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Rough running 95 Blazer

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Old 02-10-2010, 08:33 AM   #1
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Rough running 95 Blazer

Ok, I've searched here, and over on Chevy Talk, trying to get some ideas on where to look for possible causes. I'm just going to cross post to here as well, since there seems to be more S-10 owners with the 4.3 V6 here. This might be long, but I'd rather have more info out to you than not enough.

Ok, A friend of mine has a 95 S-10 blazer with CPS injection. After we replaced the head gaskets, it's developed a rough idel/run/miss condition. We've already replaced the distributor,cap, rotor,wires and plugs, along with a fuel filter trying to get rid the rough run/miss. We've even cleaned out the EGR, as it was clogged, and replaced a couple of sensors, as gas mileage had dropped to terrible. It runs even worse when it gets wet, but runs good on the highway with your foot into it. The ses light comes on when it feels like it, and sometimes even flashes. I don't have a code reader (I only own 1 OBD2 vehicle, and haven't needed it), but we are looking at borrowing one to see what codes it'll throw. Also, I don't have a fuel pressure gauge. It does blow black smoke on fire up, and seems to run better when cold than warmed up.
I'm beginning to think either the fuel pressure regulator, the lines under the cover, or possibly a clogged map sensor.Any ideas that we could check? We're looking at pulling it in over the up coming weekend, and see if we can figure out what's wrong.
Ok, a little more info. The truck was taken to Autozone to get the codes read. It coughed up, multiple miss fires. Well, we knew that already just by driving it. Anyway, another friend suggested a coil swap, or the module that resides next to the coil being a possible culprit. We're looking at what could make it run like crap, and what could make it even worse after it gets wet (like after a car wash). We're still not sure on the spider/regulator, as it runs good as long as you keep your foot in it, and that wouldn't / shouldn't make it worse when wet.
We replaced the front O2 sensor, but haven't done the rear yet. The codes weren't printed out at the zone, so I don't know what the actual numbers are. Head gaskets were replaced about 5 months ago, due to the gasket blowing thru at the very rear of #5 cylinder just above the locating dowel pin (standard place they go, even on V8's). We used Felpro head gaskets, intake manifold gaskets, and the plenum gasket. Distributor was pulled, and the new one was indexed and dropped right back in place. A new module was put in while we were there as well. It has a roll pin to locate it to the manifold, so it's gotta be pretty close, and you can't fine tune them for a tooth being off. The TPS was replaced, and the MAF was cleaned with electrical cleaner, and re-installed. We do have a spare of both though, as we're still hunting down the problem, and nothing has been thrown away. The plugs looked real good (Bosch platinums, but were replaced with Rapid Fires),with a nice clean burn. That's what's throwing me off. He told me that removing the vac hose to the vac ball on the hood made it run a little smoother, until the computer caught up. We're both thinking is an electrical issue, due to it running worse when it gets wet. I mean a FPR or a nut kit won't change if the outside were wet, but this thing runs terrible after a car wash. Can the ECM go bad intermittantly? We do have a line on one, IF needed. Thanks for any help or ideas, as we're grasping at straws.
Also, I'd like to thank gchemist for his help over on Chevy talk, as he's tried to give me some ideas. Thanks again for any help.
Old 02-11-2010, 10:48 PM   #2
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Re: Rough running 95 Blazer

WOW 20 views, and not a single piece of advice or help. I guess it's time to just toss a 4 barrel carb on it, and call it good. I thought this was supposed to be THE site for S-10 owners to get help.

Sorry for the rant, but I was hoping to kick around some ideas on what the problem might be, but I guess I won't be getting any help here. Now I remember why I sold my 88 S-10 Extended cab, and left here back in 2002. Bye.

Last edited by 97countytrk; 02-11-2010 at 10:50 PM. Reason: Added more text.
Old 02-12-2010, 03:06 AM   #3
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Re: Rough running 95 Blazer

if you suspect a fuel leak inside the intake, then you need to pull out the manifold tuning valve and look inside the bottom of the intake for small puddles and smell for any gas at all....also make sure yo do a fuel pressure check with the system primed and also running.......
Old 02-12-2010, 03:08 AM   #4
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Re: Rough running 95 Blazer

if you suspect a fuel leak inside the intake, then you need to pull out the manifold tuning valve and look inside with a flashlight at the bottom of the intake for small puddles and smell for any gas at all....also make sure yo do a fuel pressure check with the system primed and also running.......
Old 02-14-2010, 09:41 PM   #5
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Re: Rough running 95 Blazer

Well, in case anyone is interested, it turned out the coil was dieing, and the EGR valve had failed. Replaced both of those items, and it's good to go.

The big problem, was a very rough idle, and it got worse (would barely run) when WET from a car wash. We knew it was an electrical problem, but didn't know where to look. The only codes that came up were P0141, P0300, P0401, and P1406, with the last 2 being EGR related, so it got swapped. The P0300 code pointed me to the coil, since I've seen them go intermitant.
Pulled the top off the manifold, and it was dry inside, no fuel leaks.
Old 02-15-2010, 12:44 AM   #6
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Re: Rough running 95 Blazer

Quote: Originally Posted by 97countytrk
WOW 20 views, and not a single piece of advice or help. I guess it's time to just toss a 4 barrel carb on it, and call it good. I thought this was supposed to be THE site for S-10 owners to get help.

Sorry for the rant, but I was hoping to kick around some ideas on what the problem might be, but I guess I won't be getting any help here. Now I remember why I sold my 88 S-10 Extended cab, and left here back in 2002. Bye.
I love how people post things and expect everyone to know the answers to their problems in a hour or so. Some of us have lives and we don't just sit around waiting for the next new problem to be posted.

Maybe those 20 veiws wasn't 20 people (your included in the count), would you rather everyone that read it reply just to tell you that they don't know, or give you half assed advise that may cost more in the long run? IMO I'd rather have quality information even if it took longer to get it.
Old 02-15-2010, 10:32 AM   #7
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Re: Rough running 95 Blazer

Quote: Originally Posted by 97countytrk
Well, in case anyone is interested, it turned out the coil was dieing, and the EGR valve had failed. Replaced both of those items, and it's good to go.

The big problem, was a very rough idle, and it got worse (would barely run) when WET from a car wash. We knew it was an electrical problem, but didn't know where to look. The only codes that came up were P0141, P0300, P0401, and P1406, with the last 2 being EGR related, so it got swapped. The P0300 code pointed me to the coil, since I've seen them go intermitant.
Pulled the top off the manifold, and it was dry inside, no fuel leaks.
thanks for posting what cureed your problem ....im glad to hear that your truck is fixed and up and running smooth again. keep us posted on anything else, thanks
Old 11-20-2010, 10:03 PM   #8
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Re: Rough running 95 Blazer

I am having the same problem with my 95 vinW. Rough idle, kicking and jerking rpms within 40-50mph. I tried cleaning the EGR, but it is completely carboned up. Going to try a new one. Already tried a MAP, didn't help at all. Hoping a new EGR will do the trick.
Old 11-23-2010, 05:00 AM   #9
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Re: Rough running 95 Blazer

EGR Replaced, MAP replaced, and Crank Sensor Replaced.. Still not any better. I also found a vacuum hose that needs a home and I cannot find a port for it. Anyone know where I can get a vacuum diagram?
Old 11-27-2010, 12:55 PM   #10
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Re: Rough running 95 Blazer

Quote: Originally Posted by tripsblazer
EGR Replaced, MAP replaced, and Crank Sensor Replaced.. Still not any better. I also found a vacuum hose that needs a home and I cannot find a port for it. Anyone know where I can get a vacuum diagram?
where is this didconnected vacuum line coming from? and also have you checked you fuel pressure with a gauge on the test port? its very common to have a leaky FPR or leaky fuel nut kit. and how are your basic tune up parts? are they in good condition?
Old 11-28-2010, 08:39 AM   #11
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Re: Rough running 95 Blazer

closing the barn door here sfter the horse is gone. As far as the smoke is concerened..there are only 3 colors of smoke,and 3 only. They each mean a different thing and can help in problem solving. Black is fuel, blue is oil and white is coolant. Always!
My coil was them oppisite of your. I would be driving and the darn thing would just die. I started carring bottled water with me. When it died, I would pour water on the coil to cool it off..crank and drive again for a few days or however the donkey thing made up its mind to stop working again. Yes, coil replacement solved it.
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