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Also A Grumpy Site User
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Discussion Starter #1
03 Sonoma, ZR2.

Going in no particular order, Dad's old truck has had an entire front end rebuild, new battery, a/c compressor, intake gaskets, PCV valve, seafoamed the crap out of it (which honestly seemed to have helped it idle)
BUT.....
it's intermittent, but it'll start, and chug, bad. random misfire. then the code for low voltage and no voltage for an 02 sensor come on, check engine light flashes, and giving it about 30 seconds, and just drive away, it clears up, light stops, and it runs goodish. It's still a little chuggy, not bad, just not super smooth, and it has (what I remember anyway) normal go when I push the peddle. (The 8 speeds and extra 135hp kind of screwed my memory for how these things normally run)...

So, now the new trick is check engine light comes on and stays, the 02 sensor code (0134,0137, and the 0300 random misfire code) and the misfire will pop in, and it will just roll along, and all of a sudden feels like it got a shot of NO2, takes off, one quick surge, and it's back to fine.
I've changed all the vacuum lines when I'd first started dinking with it. It's doing it after sitting all night, or running in a store, and it'll go a day or two with no issues.

I am wondering if maybe the cap has a little crack in it, but I would think that would be more "cold" or "hot", and it's done it at 30 degrees, and today it was 90. Also engine temp doesn't change anything, warm, cold, just ran, sat all night.... it's making me insane.

Anyone have any ideas aside from the distrib/fuel filter/plugs-wires route?
 

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2002 S10 4.3L 3-button 4x4 3 door, 1984 S15 2.8L extended cab 5 speed
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the plugging along then sudden surge of power was something my nephew's dakota had. Oddly enough it went away after replacing the pcv valve. His was sticking closed. Not a s10 but maybe that'll help
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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1,193 Posts
check ALL your grounds- batt to frame, batt to block, batt to rad support,and the ones at the back of block to the firewall and ecm mount.
 

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Also A Grumpy Site User
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Discussion Starter #4
The PCV valve was actually the first thing I changed, along with vac lines.

I literally was wondering about ground this evening after work, It had a little of the "idle pulse" in the headlights at night, so i will probably try that tonight.
Buddy at the shop is really wondering if there isn't a small head gasket leak and it's filling up a cylinder just enough to foul it for a minute, but I would see that as an ever single start type of problem, and this isn't.
 

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2002 S10 4.3L 3-button 4x4 3 door, 1984 S15 2.8L extended cab 5 speed
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I don't know how i missed that you'd changed the PCV VALVE already. I made an account here just to answer this question because it drove me nuts on my nephews dakota. But maybe this will help. Circuit 31 goes to the rear o2 sensor. 2 separate grounds. Says both on rear of engine left and right side for the o2 sensors.

341930
 

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Also A Grumpy Site User
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Discussion Starter #6
oh no you didn't miss it, i had forgot about it until you'd typed it and i remember that was the first thing I had done, and it had the frappachino look stuck to it, that then led to the intake gaskets getting done. so that's totally my fault, you were right, but i will check those wires too, that is what it's acting like, a wiring issue, not really a mechanical issue, i would think something broke/leaking/whatever would be a problem every single time, not just every random however often it feels like doing something crazy.

another really weird thing, that engine light will be solid, throwing an O2 code, flashing, with the random misfire, or just totally shuts off.... BUT, I noticed today, even sitting outside for 5 or 6 hours, it'll start over 100 degrees, roughly the 2nd mark above 100, and rises to full operating temp within 90 seconds. granted, it's beeen 90 degrees, but I've never seen an engine do that. the guy I had taken it to for the front end had hooked it up and re-timed it, and said it was like 12 degrees off, he said he just has this hunch it's got a head problem, said he saw some wet on the side that looked fresh, and i just hope that's not what i'm staring down.
 

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2002 S10 4.3L 3-button 4x4 3 door, 1984 S15 2.8L extended cab 5 speed
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In my experience wet is usually a valve cover not a head issue. Since there's so much pressure there it tends to not be intermittent. Pull one of the easier plugs and check them. Mine was supposed to have fine wire and someone put standard Champions in 5 cylinders. It had random misfires at first. Those went away after i changed the plugs and wires. Though i did give myself a misfire in cylinder 6 because i missed the plug when putting the wire on. Very embarrassing when i noticed it with the fender off.

Never heard of a vehicle hitting op temp in 90 seconds. That sounds like a very lean condition. Maybe wiggle the o2 wire when it's running to see if you get the issue. They determine fuel air mixture based on their readings.
 

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Also A Grumpy Site User
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Discussion Starter #8
I appreciate it, been texting the town genius (I'm actually not even being sarcastic, he's like, idk... motor Jesus) and it looks like the ol' Noma is going to go over and get hooked up and ran, see if he can get some data while moving it.

I returned my lease, thinking this was running okay, and then my luck kicked in. But I live in a tiny town, overrun with methheads, but I work in rent to own, so it's not like I don't know who is who anyway lol I just may be getting some exercise while it's hanging out at the shop.

If I don't just take it to the crusher, I'll let ya know what I find out lol
 

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2002 S10 4.3L 3-button 4x4 3 door, 1984 S15 2.8L extended cab 5 speed
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I know that temptation to send to the crusher. With mine it's a 4x4 and i typically avoid that. But the truck was cheap. I would have had it looking and running brand new by now if not for the 4x4 system. One thing after another. So many little things but at least i can find mine. Those hidden demons like yours drive you nuts. If you do figure it out, fixable or not, let us know. Might save someone else days of trouble.
 

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Also A Grumpy Site User
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Discussion Starter #10
Well, it started knocking when I started it tonight. So, there's that.
Being my Dad's truck or not, it wasn't like "his baby" or anything, he just liked the fact that 4x4 got him through all the winter. Might do some parting out and then scrap the rest, might see if I can get much of anything of it from a trade in.
Honestly I am starting to think he just doesn't want me driving it, just keep getting these problems haha, but I'm not putting a motor in it, because if I did that I'd go on a fresh build, and that's going to cost what the truck is worth, and there's not sentimental value to me for that.
 

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I had a random miss fire code that had me chasing my tail for days....Ended up being a intermittent bad iac.
i was watching the idle be controlled one day and missing the next. Would not even start some days, was stuck open i guess..
 

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Also A Grumpy Site User
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Discussion Starter #12
Well, I actually tried to take it in today, and it backfired about half a dozen times, the check engine light shut off, and it's running fine. I dumped an entire bottle of seafoam in the gas, it had sat for a while, and it smelled pretty rich, and I am starting to wonder if I broke a bunch of crap loose in the tank. I ended up taking it on a, maybe 80 mile highway run, and it ran just fine, not a hiccup, shut off, restarted. I'm telling you guys that thing is haunted.
 

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Well, I actually tried to take it in today, and it backfired about half a dozen times, the check engine light shut off, and it's running fine. I dumped an entire bottle of seafoam in the gas, it had sat for a while, and it smelled pretty rich, and I am starting to wonder if I broke a bunch of crap loose in the tank. I ended up taking it on a, maybe 80 mile highway run, and it ran just fine, not a hiccup, shut off, restarted. I'm telling you guys that thing is haunted.
Wait. Something doesn't add up here. You said your truck was knocking, which is a mechanical rod bearing issue and no amount of troubleshooting is going to fix that diagnosis beyond replacing the bearings. Now, you said that you took it on a run and it was fine. So, was it not actually knocking before, or are you now convinced that knocking is fine? Or was it not really knocking and you just said it was to discourage anyone from offering you any more troubleshooting advice?
 

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Also A Grumpy Site User
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Discussion Starter #14
well, i'd need to be steven king to put everything that this weirdo has done, but i sure thought it was knocking, it started backfiring, but instead of sitting still, i was trying to drive, and i realized with the little surge/pop/surge/pop what was going on, so i guess now i'm just an idiot, and it was backfiring on me the other day too.

what does everything think about a gummed up injector? it smelled gassy again tonight, but the real issue is it's doing something different every time i start it. if it was sticking open, dumping fuel, that should cause a misfire, and a backfire, right? and if it stuck shut, that could get that running lean getting hot fast too? i don't want to replace everything in the truck, but to be quite honest, I don't really want to let it beat me either haha
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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back fire is a firing issue -not fuel.Plus that "knock" could have been a knock -knock- fuel getting ignited early. Start by pull your cap- check for scoring and arc tracing inside.check your rotor- does it turn?is it burnt?. if it turns AT ALL, you have a problem with either the rotor or the dizzy.Next would be plugs and wires.start simple.- your plugs can tell you what is happening in the cyclinders by how they look.
 
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Also A Grumpy Site User
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Discussion Starter #16
i just woke up and realized something-on the highway, which i've been dumb enough to try a couple times, it will shut off the check engine light, and runs good. after a couple of restarts of being in town, which i'm in a "5 minutes to either end of town" sized town, the light comes back on and the bogging/whatever/psycho running starts again.
123K miles, I was thinking just completely new distrib-is it still only using the ac delco ones? i remember YEARS ago that they were the only one that was worth it because a lot of people had bought store brand stuff and still had problems, only to ultimately change the distrib again and it fixed it.
 

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Also A Grumpy Site User
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Discussion Starter #17
back fire is a firing issue -not fuel.Plus that "knock" could have been a knock -knock- fuel getting ignited early. Start by pull your cap- check for scoring and arc tracing inside.check your rotor- does it turn?is it burnt?. if it turns AT ALL, you have a problem with either the rotor or the dizzy.Next would be plugs and wires.start simple.- your plugs can tell you what is happening in the cyclinders by how they look.
Okay I ordered a new ac delco cap and rotor, it'll be here end of week and a set of plugs, but, the o'reilly dude handed me some (they're out in the truck and i don't remember for sure) platinum that i read isn't so hot with distributors but better with the new distrib-less ignitions. so i presume it's probably best to switch to something else, i had just told the guy to hand me 6 factory replacements and that's what I got, I haven't kept up with plugs since the birth of the 4 prong "ever spark every where" BS back in like 1999 lol

but, I've been really paying attention, when it's all loaded up, it's gassy smelling, the wind was blowing from the rear and I finally smelled it, so it's chugging while i start rolling, and decide to just floor it, clears it up within a couple seconds.
I appreciate it guys, I'll report back after I get those all swapped out and see what she does
 

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94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
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platinum was oem - but he should have given you iridium- that replaced the platinum about 2010- and stay away from the multi tip plugs- they do not fair to well with the chamber setup on our stock heads.
 

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Also A Grumpy Site User
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Discussion Starter #19
oh okay, yea i remember all sorts of multi-tip plug issues back in the day, wish i was still young and that's all the stuff i needed to know about lol
 

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Discussion Starter #20
Great news everyone!

(That's a Futurama reference)

anywho... cap and rotor came, figured I can get those changed and get the plugs once I can get the fronts off it so I can reach, and lookie what I found->
Just did a quick run around a couple blocks, idles smoother and the throttle response is of course quite a bit better. I was leasing a brand new ram, so going backwards to this, honestly I just couldn't tell because of the overall difference in the truck and power... so yes, I feel stupid for not pulling that first. i think i'll be off at 4 saturday, so if it's not bbq fat guy weather (Me being the bbq in the heat) I will probably change them then and get that done up, see if that does a little bit more. That dizzy, it's so.... disgusting.
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