86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the time

ddog800 · 10-12-2009, 01:29 AM

I'm having a rather frustrating problem. I've got a 86 s-10 blazer, 2.8 TBI. It runs beautifully when I first start it up and will do so for as long as 30 or 45 minutes if I just leave it on the driveway running, but after a while it begins to stumble and want to stall out, and it will backfire into the throttle body. If I start it and take off it may run great for a few miles and then it starts stalling and misfiring and backfiring into the t.b. In some cases it will do that for miles, in one case it stalled out completely and refused to start stranding me. So far I've been chasing my tail with this issue. I thought initially it might be a clogged fuel filter, so I changed it out, but it had no effect. At times it will stall out and won't start back for a while. I checked and am definitely getting good fire to the plugs, and I can also see both of the injectors spraying what looks to be the normal amount of fuel that I usually see them spraying. However, once it hits this no start condition it simply will not start unless I let it sit for a while, despite getting fire and fuel. Even checked the timing, which was a bit out, and after sorting it out it does run much smoother when it's running. Sometimes after it begins to stumble and backfire it will do it for a few minutes and then begin running great again. It's very intermittent and quite frustrating. I removed the EGR and inspected it, but it didn't appear to be that dirty and didn't appear clogged, though there was some carbon buildup. Also checked the diaphram and it didn't seem to be broken at all. In the process of working out another issue, I've also replaced the ICM and the ECM, but they've also had no effect on this particular issue. I'm starting to run out of ideas short of just randomly replacing stuff, but that's not the proper solution. I'd really appreciate any ideas on this!

Thanks in advance

Revolt · 10-12-2009, 02:10 AM

Test your ignition control module and pickup coil.

Edit re-read you've tested the ICM, test the pickup coil.

bobditts · 10-12-2009, 02:17 AM

I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM.

ddog800 · 10-12-2009, 10:00 AM

Quote: Originally Posted by Revolt

Test your ignition control module and pickup coil.
Edit re-read you've tested the ICM, test the pickup coil.

I didn't check the coil directly, but I did verify that I'm getting nice hot fire to each of the plugs. I put a timing light on each wire and it went off as i would have expected it, and I also removed each spark plug wire and had someone turn it over while I held it close to the block with a long nail sticking out of the end. Each time I got a nice blue spark. Not sure how definitive that is, but it would seem to indicate I'm getting good fire from the coil.

Quote: Originally Posted by bobditts

I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM.

I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon.

ddog800 · 10-12-2009, 02:11 PM

Quote: Originally Posted by bobditts

I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM.

Quote: Originally Posted by ddog800

I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon. I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon.

Well, I checked the TPS. It was out just a bit, was reading about .32v . I readjusted it to about .43v, but it had no effect. The problem is still there. It will run excellent for a bit, then start to stutter and backfire. Any other ideas?

Revolt · 10-12-2009, 02:18 PM

Are you getting spark when the problem occurs ?

Its hard to exactly know without seeing the symptoms in person. I would however test the pickup coil that is underneath the distributor cap.

Or you throwing any codes ?

bobditts · 10-12-2009, 02:26 PM

how old is the gas tank? Maybe you have debris in the tank that gets stirred up while you drive and restricts the gas flow?

ddog800 · 10-12-2009, 02:42 PM

Quote: Originally Posted by Revolt

Are you getting spark when the problem occurs ?

Its hard to exactly know without seeing the symptoms in person. I would however test the pickup coil that is underneath the distributor cap.

Or you throwing any codes ?

I haven't tested the pickup coil under the cap, but I have been wondering if I might be having a distributor problem. I can tell you that when it hit a complete no-start condition I was able to confirm that I was getting spark all the way out to the wires. Can you tell me the best way to test the pickup coil on the distributor?

As for codes, I don't yet know that (and I may find a plethora of answers there, maybe not) because the Service Engine Soon bulb on the instrument panel is gone out. Last night I ordered an ALDL cable to connect to my laptop with some software so I can read the codes out that way. I'm hoping to get some good info from it.

Quote: Originally Posted by bobditts

how old is the gas tank? Maybe you have debris in the tank that gets stirred up while you drive and restricts the gas flow?

As for the gas tank, I have been suspecting it since this problem started. I initially changed out the fuel filter hoping that was it, but it didn't fix it. That said, the filter that was on it was completely filled with rust. When I first removed the input hose some nasty red/brown liquid came out of the bottom of the filter. After it sat for a few days I can shake the old filter and powdered rust comes out. It may very well be that there is crap in the tank. I have considered dropping the tank and taking a look, possibly replacing it, but haven't gotten that far yet. Not something I'm looking forward to doing and was hoping to weed some other possible problems out first.

I did confirm this morning that it doesn't have anything to do with heat. When i initially turned it on this morning it barely ran for 2 minutes before it started acting up. The engine was still cool enough that I could touch it, and the temp gauge hadn't even moved yet. Then it cleared right up and ran like a champ for about 30 or so minutes.

Thanks for the assistance guys!

ddog800 · 10-17-2009, 02:13 PM

Well, here's an update. I finally had some time to play around with this thing yesterday. We've finally gotten that perfect 60F breezy weather down here, so I know what I'll be doing for the next solid few weeks

.

In the past few days the truck had degraded to the point to where it wouldn't even try to run smoothly. It was constantly sputtering, and often it wouldn't even start. I could see the fuel injectors spraying down into the throttle body so I knew it was getting fuel. I pulled multiple plugs and was getting nice hot fire from each one I tried. And when it would stumble it would occasionally backfire back through the throttle body with a much larger flame than I think is safe for the well-being of my TBI components. So, I'm getting fuel, fire... hmmm only thing left is air. After fighting it for about 30 mins, mostly just trying to ensure that it wasn't working before I started changing or removing things, I went around and pulled the PCV valve. Lo and behold the truck started right up and was even idling rather higher than normal, about 1200 - 1300 rpm. I turned it off and on a few times and it barely made one rotation before it started every time, revved up great. I ran down the road and grabbed a new valve and installed it. Made sure to clean out the hose going from the valve to the TBI and all that good stuff. After doing so it ran for a solid hour beautifully. At one point near the end of that it actually did stumble and stutter for about 30 seconds, which made me uncomfortable, then it went back to running perfectly, so I stopped it for a few mins and let it rest.

When it turned it back on it was running great again. I decided to take it around the block. I barely made it around before it was right back to doing exactly what it was doing before. I parked it and let it sit for about 10 mins, then tried to start it again and it did the same thing. I then let it sit for a good hour or so. I went back out, started it up, and it ran perfectly. I took it around the block again, and this time, at first, it was great. Got it up to about 50 with no problems, it was running awesome. After a few minutes of it running awesome, it started the stumbling and stuttering again. I took it home and parked it again. This morning, I just started it up in the yard and it's running great, a solid hour and a half with no problems.

I'm now thoroughly convinced I'm fighting multiple problems here. I have no doubt my PCV valve was causing part of the trouble. It was one of the parts I hadn't gotten to checking out yet (stupid since it's so accessible and only 2 bucks to replace, but hey, live and learn). It did run consistently like crap for a few days until the moment I removed it, so I'm convinced it was part of the problems. Now, the stumbling and backfiring issue remains, but it's very intermittent again and it's running better more often than not. However, after taking it out on the road each time it doesn't take long before it starts crapping out again.

I'm almost wondering if I have crap in my tank or something that's randomly inhibiting fuel flow. Next thing I'm going to try is to attempt to monitor fuel pressure while it's in the stumbling/studdering condition (if I can sort out issues with how best to do that. If you have any ideas please let me know, or check out my other post regarding that here.)

Hopefully I can reply to this in the next day or so with my final solution to this issue for anyone else who may come along experiencing the same thing.

ddog800 · 10-17-2009, 09:45 PM

Another update. I decided to extract some gas from the tank. I removed the rubber fuel inlet hose from the bottom of the fuel filter and aimed it at a clean bucket, then had someone hit my fuel pump switch in the cab....

I don't think my truck likes red gas. :P ... I let it spray a few cups of gas into the bucket, and by the time it evaporated it left mass quantities of red powder behind. It was so thick with red/brown color that it was no longer a transparent liquid in the slightest. I did the same test after letting it sit for about an hour or so and then put yet more gas into the bucket (after cleaning it again). Same thing. It's down to about a 1/4 tank at this point.

I believe I'll be dropping this tank and replacing it tomorrow. I can get actually get a 20 gallon tank here in town for less than $100, so i think I'll be doing that. I get the feeling this is 90% of the remainder of my problem.

Will post tomorrow.

bobditts · 10-17-2009, 11:18 PM

red meaning rust? Ya, a new tank sounds like its in order!

ddog800 · 10-18-2009, 01:34 AM

yep, red meaning rust... bad rust :P.... will be ordering one first thing in the morning.

ddog800 · 10-22-2009, 12:39 PM

Well, I hope I'm not speaking too soon, but I believe this problem is SOLVED! It appears that my initial instinct was correct (clogged fuel system) as well as bob's suggestion (trash getting stirred up in the fuel tank as it runs).

I completed the fuel tank replacement yesterday and went ahead and replaced the fuel filter again as well (for good measure) and everything is working wonderfully thus far. I went ahead and upgraded it to the 20 gallon tank and replaced the sender/float assembly as well, so it's all brand new except for the pump (which, despite processing the bad gas for a few weeks, is still a fairly new and unused AC Delco pump). Took it for a spin around town last night for about 30 or 45 mins with no problems, and then drove it into work this morning also with no problems. It's running better than ever (not surprisingly). In the process of troubleshooting this mess, I've adjusted the timing, tweaked on the TPS adjustment, revamped my vacuum system, tightened belts, replaced the PCV valve, cleaned the EGR valve, etc etc. and it's all showing now that I can drive it around again.

I will post some pics later this afternoon of what the old tank was looking like. The sock filter that's attached to the intake side of the fuel pump was so caked up with rust it was unbelievable. Once it dried out I had chunks of rust flaking off of it that was at least a 1/2" or more thick. In hindsight, it's amazing this thing was running at all. The interesting thing is, for the most part my injectors were still always firing into the throttle body even when it wouldn't start or would begin to run badly, so that just goes to show how much the volatility of the gas was being affected.

The installation of the new tank went fairly well, except for a minor snag here or there, mostly having to do with going from a 13 gallon to a 20 gallon tank. The tanks were dimensionally almost identical, but the only real issue we encountered was when trying to adjust the straps that route above the tank to increase the vertical space for the slightly-taller 20 gallon tank. There is a bolt for each upper-strap accessible between the top of the bumper and the body on either side of the license plate that is to be loosened as-needed. Unfortunately the bolts were so rusted up and caked with crap that it was almost impossible to loosen them enough. Despite using penetrating oil and whatnot, I still broke a bolt on the drivers side upper strap, so I just went ahead and broke off the one on the other side as well so I could get the tank on. As it happens, there was still barely enough clearance to get the bottom straps mounted on and the top is pushed well into the body on the topside, so I don't anticipate any play that would cause the tank to bounce around. It was nice and snug. After a day or 2 of driving I'll get back under the truck and try to jockey the tank back and forth to ensure that there is no play. Also, I'm going to let this fuel filter catch any rust left behind in the fuel system for a month or 2 and then change it out again to try and remove as much as possible from circulation.

Thanks for your help everyone.

bobditts · 10-22-2009, 06:39 PM

glad I could help!!! I feel I will have to do the same thing soon.

ddog800 · 10-23-2009, 10:40 AM

Indeed, I'm actually glad it worked out this way because the engine runs so much smoother overall now than it has in years. Now, if I can just take care of this leaky oil pan (or at least slow it down a bit) without having to have the engine pulled, I'll really be doing something

, but that's for another thread I suppose.

bobditts · 10-23-2009, 06:36 PM

leaky oil pans are just part of these engines I think. I pulled my engine a few months ago, had the engine upsidown, replaced the gasket and pan, let it seal for 3 days, then flipped it back over and it still leaks!

ddog800 · 10-24-2009, 07:56 PM

Ouch! I'd be happy if I can just slow mine a bit. I'm losing about a quart or more a week and it's smokes from under the vehicle where it drips onto the exhaust... rather nasty.

dB-r · 10-24-2009, 11:37 PM

On the full size TBI trucks I have owned in the past, seems like stumble or weird idle problems were almost always either clogged passages on the bottom of the throttle body for the PCV and IACV, or bad ignition control module.

Hope its fixed now!

dB-r · 10-24-2009, 11:38 PM

Oh and bad EGR also, but that's an easy one to troubleshoot, just unplug the vacuum from it and plug off the hose, then drive, if it now runs fine, but the computer throws a code, even though it's running fine, then you need a new EGR.

dB-r · 10-24-2009, 11:49 PM

there is other great one that I have experienced... I had a 92 4.3 v6 full size truck, which got harder and harder to start, I would crank on it for what seemed like forever before it would finally fire up.

Then it quit. I assumed it was the fuel pump. Dropped the tank, put in a new pump, same problem... LOL. Opened the hood, tapped gently on the fuel pump relay mounted to the firewall and it started right up.... I felt dumb. Was just a bad relay...

ddog800 · 10-27-2009, 05:08 PM

Yep, still running great, so I think i got it licked. Hate to hear about your experience with the relay, dropping the tank sucks when you didn't need to do it. One of the reasons I spent a week troubleshooting every stupid little thing on this before I broke down and dropped the tank :P

10-12-2009, 01:29 AM	#1
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the time I'm having a rather frustrating problem. I've got a 86 s-10 blazer, 2.8 TBI. It runs beautifully when I first start it up and will do so for as long as 30 or 45 minutes if I just leave it on the driveway running, but after a while it begins to stumble and want to stall out, and it will backfire into the throttle body. If I start it and take off it may run great for a few miles and then it starts stalling and misfiring and backfiring into the t.b. In some cases it will do that for miles, in one case it stalled out completely and refused to start stranding me. So far I've been chasing my tail with this issue. I thought initially it might be a clogged fuel filter, so I changed it out, but it had no effect. At times it will stall out and won't start back for a while. I checked and am definitely getting good fire to the plugs, and I can also see both of the injectors spraying what looks to be the normal amount of fuel that I usually see them spraying. However, once it hits this no start condition it simply will not start unless I let it sit for a while, despite getting fire and fuel. Even checked the timing, which was a bit out, and after sorting it out it does run much smoother when it's running. Sometimes after it begins to stumble and backfire it will do it for a few minutes and then begin running great again. It's very intermittent and quite frustrating. I removed the EGR and inspected it, but it didn't appear to be that dirty and didn't appear clogged, though there was some carbon buildup. Also checked the diaphram and it didn't seem to be broken at all. In the process of working out another issue, I've also replaced the ICM and the ECM, but they've also had no effect on this particular issue. I'm starting to run out of ideas short of just randomly replacing stuff, but that's not the proper solution. I'd really appreciate any ideas on this! Thanks in advance
	[Reply w/Quote]

10-12-2009, 02:10 AM	#2
Revolt Registered User Join Date: Oct 2009 Posts: 24 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Test your ignition control module and pickup coil. Edit re-read you've tested the ICM, test the pickup coil. Last edited by Revolt : 10-12-2009 at 02:16 AM.
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10-12-2009, 02:17 AM	#3
bobditts banned Age: 25 Join Date: Aug 2008 Posts: 947 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM.
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10-12-2009, 10:00 AM	#4
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Quote: Originally Posted by Revolt Test your ignition control module and pickup coil. Edit re-read you've tested the ICM, test the pickup coil. I didn't check the coil directly, but I did verify that I'm getting nice hot fire to each of the plugs. I put a timing light on each wire and it went off as i would have expected it, and I also removed each spark plug wire and had someone turn it over while I held it close to the block with a long nail sticking out of the end. Each time I got a nice blue spark. Not sure how definitive that is, but it would seem to indicate I'm getting good fire from the coil. Quote: Originally Posted by bobditts I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM. I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon.
	[Reply w/Quote]

10-12-2009, 02:11 PM	#5
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Quote: Originally Posted by bobditts I have the exact same vehicle. Mine used to run like garbage as well. Not quite as bad as yours but the biggest improvement I saw was readjusting the TPS. Make sure it is properly set with a DMM. Quote: Originally Posted by ddog800 I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon. I haven't taken a look at the TPS yet, I'll go ahead and check that out this afternoon. Well, I checked the TPS. It was out just a bit, was reading about .32v . I readjusted it to about .43v, but it had no effect. The problem is still there. It will run excellent for a bit, then start to stutter and backfire. Any other ideas?
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10-12-2009, 02:18 PM	#6
Revolt Registered User Join Date: Oct 2009 Posts: 24 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Are you getting spark when the problem occurs ? Its hard to exactly know without seeing the symptoms in person. I would however test the pickup coil that is underneath the distributor cap. Or you throwing any codes ?
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10-12-2009, 02:26 PM	#7
bobditts banned Age: 25 Join Date: Aug 2008 Posts: 947 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t how old is the gas tank? Maybe you have debris in the tank that gets stirred up while you drive and restricts the gas flow?
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10-12-2009, 02:42 PM	#8
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Quote: Originally Posted by Revolt Are you getting spark when the problem occurs ? Its hard to exactly know without seeing the symptoms in person. I would however test the pickup coil that is underneath the distributor cap. Or you throwing any codes ? I haven't tested the pickup coil under the cap, but I have been wondering if I might be having a distributor problem. I can tell you that when it hit a complete no-start condition I was able to confirm that I was getting spark all the way out to the wires. Can you tell me the best way to test the pickup coil on the distributor? As for codes, I don't yet know that (and I may find a plethora of answers there, maybe not) because the Service Engine Soon bulb on the instrument panel is gone out. Last night I ordered an ALDL cable to connect to my laptop with some software so I can read the codes out that way. I'm hoping to get some good info from it. Quote: Originally Posted by bobditts how old is the gas tank? Maybe you have debris in the tank that gets stirred up while you drive and restricts the gas flow? As for the gas tank, I have been suspecting it since this problem started. I initially changed out the fuel filter hoping that was it, but it didn't fix it. That said, the filter that was on it was completely filled with rust. When I first removed the input hose some nasty red/brown liquid came out of the bottom of the filter. After it sat for a few days I can shake the old filter and powdered rust comes out. It may very well be that there is crap in the tank. I have considered dropping the tank and taking a look, possibly replacing it, but haven't gotten that far yet. Not something I'm looking forward to doing and was hoping to weed some other possible problems out first. I did confirm this morning that it doesn't have anything to do with heat. When i initially turned it on this morning it barely ran for 2 minutes before it started acting up. The engine was still cool enough that I could touch it, and the temp gauge hadn't even moved yet. Then it cleared right up and ran like a champ for about 30 or so minutes. Thanks for the assistance guys!
	[Reply w/Quote]

10-17-2009, 02:13 PM	#9
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Well, here's an update. I finally had some time to play around with this thing yesterday. We've finally gotten that perfect 60F breezy weather down here, so I know what I'll be doing for the next solid few weeks . In the past few days the truck had degraded to the point to where it wouldn't even try to run smoothly. It was constantly sputtering, and often it wouldn't even start. I could see the fuel injectors spraying down into the throttle body so I knew it was getting fuel. I pulled multiple plugs and was getting nice hot fire from each one I tried. And when it would stumble it would occasionally backfire back through the throttle body with a much larger flame than I think is safe for the well-being of my TBI components. So, I'm getting fuel, fire... hmmm only thing left is air. After fighting it for about 30 mins, mostly just trying to ensure that it wasn't working before I started changing or removing things, I went around and pulled the PCV valve. Lo and behold the truck started right up and was even idling rather higher than normal, about 1200 - 1300 rpm. I turned it off and on a few times and it barely made one rotation before it started every time, revved up great. I ran down the road and grabbed a new valve and installed it. Made sure to clean out the hose going from the valve to the TBI and all that good stuff. After doing so it ran for a solid hour beautifully. At one point near the end of that it actually did stumble and stutter for about 30 seconds, which made me uncomfortable, then it went back to running perfectly, so I stopped it for a few mins and let it rest. When it turned it back on it was running great again. I decided to take it around the block. I barely made it around before it was right back to doing exactly what it was doing before. I parked it and let it sit for about 10 mins, then tried to start it again and it did the same thing. I then let it sit for a good hour or so. I went back out, started it up, and it ran perfectly. I took it around the block again, and this time, at first, it was great. Got it up to about 50 with no problems, it was running awesome. After a few minutes of it running awesome, it started the stumbling and stuttering again. I took it home and parked it again. This morning, I just started it up in the yard and it's running great, a solid hour and a half with no problems. I'm now thoroughly convinced I'm fighting multiple problems here. I have no doubt my PCV valve was causing part of the trouble. It was one of the parts I hadn't gotten to checking out yet (stupid since it's so accessible and only 2 bucks to replace, but hey, live and learn). It did run consistently like crap for a few days until the moment I removed it, so I'm convinced it was part of the problems. Now, the stumbling and backfiring issue remains, but it's very intermittent again and it's running better more often than not. However, after taking it out on the road each time it doesn't take long before it starts crapping out again. I'm almost wondering if I have crap in my tank or something that's randomly inhibiting fuel flow. Next thing I'm going to try is to attempt to monitor fuel pressure while it's in the stumbling/studdering condition (if I can sort out issues with how best to do that. If you have any ideas please let me know, or check out my other post regarding that here.) Hopefully I can reply to this in the next day or so with my final solution to this issue for anyone else who may come along experiencing the same thing. Last edited by ddog800 : 10-17-2009 at 02:20 PM.
	[Reply w/Quote]

10-17-2009, 09:45 PM	#10
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Another update. I decided to extract some gas from the tank. I removed the rubber fuel inlet hose from the bottom of the fuel filter and aimed it at a clean bucket, then had someone hit my fuel pump switch in the cab.... I don't think my truck likes red gas. :P ... I let it spray a few cups of gas into the bucket, and by the time it evaporated it left mass quantities of red powder behind. It was so thick with red/brown color that it was no longer a transparent liquid in the slightest. I did the same test after letting it sit for about an hour or so and then put yet more gas into the bucket (after cleaning it again). Same thing. It's down to about a 1/4 tank at this point. I believe I'll be dropping this tank and replacing it tomorrow. I can get actually get a 20 gallon tank here in town for less than $100, so i think I'll be doing that. I get the feeling this is 90% of the remainder of my problem. Will post tomorrow.
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10-17-2009, 11:18 PM	#11
bobditts banned Age: 25 Join Date: Aug 2008 Posts: 947 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t red meaning rust? Ya, a new tank sounds like its in order!
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10-18-2009, 01:34 AM	#12
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t yep, red meaning rust... bad rust :P.... will be ordering one first thing in the morning.
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10-22-2009, 12:39 PM	#13
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Well, I hope I'm not speaking too soon, but I believe this problem is SOLVED! It appears that my initial instinct was correct (clogged fuel system) as well as bob's suggestion (trash getting stirred up in the fuel tank as it runs). I completed the fuel tank replacement yesterday and went ahead and replaced the fuel filter again as well (for good measure) and everything is working wonderfully thus far. I went ahead and upgraded it to the 20 gallon tank and replaced the sender/float assembly as well, so it's all brand new except for the pump (which, despite processing the bad gas for a few weeks, is still a fairly new and unused AC Delco pump). Took it for a spin around town last night for about 30 or 45 mins with no problems, and then drove it into work this morning also with no problems. It's running better than ever (not surprisingly). In the process of troubleshooting this mess, I've adjusted the timing, tweaked on the TPS adjustment, revamped my vacuum system, tightened belts, replaced the PCV valve, cleaned the EGR valve, etc etc. and it's all showing now that I can drive it around again. I will post some pics later this afternoon of what the old tank was looking like. The sock filter that's attached to the intake side of the fuel pump was so caked up with rust it was unbelievable. Once it dried out I had chunks of rust flaking off of it that was at least a 1/2" or more thick. In hindsight, it's amazing this thing was running at all. The interesting thing is, for the most part my injectors were still always firing into the throttle body even when it wouldn't start or would begin to run badly, so that just goes to show how much the volatility of the gas was being affected. The installation of the new tank went fairly well, except for a minor snag here or there, mostly having to do with going from a 13 gallon to a 20 gallon tank. The tanks were dimensionally almost identical, but the only real issue we encountered was when trying to adjust the straps that route above the tank to increase the vertical space for the slightly-taller 20 gallon tank. There is a bolt for each upper-strap accessible between the top of the bumper and the body on either side of the license plate that is to be loosened as-needed. Unfortunately the bolts were so rusted up and caked with crap that it was almost impossible to loosen them enough. Despite using penetrating oil and whatnot, I still broke a bolt on the drivers side upper strap, so I just went ahead and broke off the one on the other side as well so I could get the tank on. As it happens, there was still barely enough clearance to get the bottom straps mounted on and the top is pushed well into the body on the topside, so I don't anticipate any play that would cause the tank to bounce around. It was nice and snug. After a day or 2 of driving I'll get back under the truck and try to jockey the tank back and forth to ensure that there is no play. Also, I'm going to let this fuel filter catch any rust left behind in the fuel system for a month or 2 and then change it out again to try and remove as much as possible from circulation. Thanks for your help everyone. Last edited by ddog800 : 10-22-2009 at 12:40 PM.
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10-22-2009, 06:39 PM	#14
bobditts banned Age: 25 Join Date: Aug 2008 Posts: 947 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t glad I could help!!! I feel I will have to do the same thing soon.
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10-23-2009, 10:40 AM	#15
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Indeed, I'm actually glad it worked out this way because the engine runs so much smoother overall now than it has in years. Now, if I can just take care of this leaky oil pan (or at least slow it down a bit) without having to have the engine pulled, I'll really be doing something , but that's for another thread I suppose.
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10-23-2009, 06:36 PM	#16
bobditts banned Age: 25 Join Date: Aug 2008 Posts: 947 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t leaky oil pans are just part of these engines I think. I pulled my engine a few months ago, had the engine upsidown, replaced the gasket and pan, let it seal for 3 days, then flipped it back over and it still leaks!
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10-24-2009, 07:56 PM	#17
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Ouch! I'd be happy if I can just slow mine a bit. I'm losing about a quart or more a week and it's smokes from under the vehicle where it drips onto the exhaust... rather nasty.
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10-24-2009, 11:37 PM	#18
dB-r Registered User Age: 35 Join Date: Oct 2009 Posts: 7 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t On the full size TBI trucks I have owned in the past, seems like stumble or weird idle problems were almost always either clogged passages on the bottom of the throttle body for the PCV and IACV, or bad ignition control module. Hope its fixed now!
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10-24-2009, 11:38 PM	#19
dB-r Registered User Age: 35 Join Date: Oct 2009 Posts: 7 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Oh and bad EGR also, but that's an easy one to troubleshoot, just unplug the vacuum from it and plug off the hose, then drive, if it now runs fine, but the computer throws a code, even though it's running fine, then you need a new EGR.
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10-24-2009, 11:49 PM	#20
dB-r Registered User Age: 35 Join Date: Oct 2009 Posts: 7 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t there is other great one that I have experienced... I had a 92 4.3 v6 full size truck, which got harder and harder to start, I would crank on it for what seemed like forever before it would finally fire up. Then it quit. I assumed it was the fuel pump. Dropped the tank, put in a new pump, same problem... LOL. Opened the hood, tapped gently on the fuel pump relay mounted to the firewall and it started right up.... I felt dumb. Was just a bad relay...
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10-27-2009, 05:08 PM	#21
ddog800 Registered User Join Date: Oct 2008 Posts: 45 Location: User is: OffLine	Re: 86 s-10 blz 2.8 tbi runs great half the time, stutters/stumbles/stalls half the t Yep, still running great, so I think i got it licked. Hate to hear about your experience with the relay, dropping the tank sucks when you didn't need to do it. One of the reasons I spent a week troubleshooting every stupid little thing on this before I broke down and dropped the tank :P
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