'90 S10 with 4.3L won't run correctly - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 01-13-2004, 02:04 PM Thread Starter
Mud in my Veins
 
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\'90 S10 with 4.3L won\'t run correctly

Wondering if any of you could give me some ideas to help with my future brother in law's S10. It's a 90 S10 4x4 with a 4.3L TBI V6 and 700R4. Standard fare, the usual rust and all that, but eh, to be expected. Problem is the engine. Has 200,000+ on it, but supposedly got a rebuild not to long after 100,000. Originally when he got it this spring it wouldn't idle. It was like an out of tune carb. It'd idle high when you started it, then settle down to maybe, maybe 800-1000rpm once it was good and warmed up. Even when warmed up, it won't idle smoothly, always bouncing between 800-1000rpm. Occasionally it'll just die while sitting there idling. You can't keep it in D and not be moving, had to put it in park or neutral. Died at stop lights, whenever he'd slow down for a stop sign, etc. Also would bog sometimes when he hit the gas. I followed him once, thing was slow, just plain slow.
He's done the total tune up, plugs, wires, cap, rotor, air filter, fuel filter, O2 sensor (what a chore on that rusty pipe), new gaskets on the TBI, and just this weekend a "new to him" TBI. Old one seemed to be sticking when it tried to open. It's doing better now, will keep running at lights in D, seems to accelerate a bit better, but not fixed at all, just better.
I'm at a loss with my meager skills. Only thing else I know is that it doesn't throw any codes and when they hooked a diagnostic computer up to it, it couldn't say what the target idle was. Showed the current idle speed, but wouldn't give a target idle. I've wondered if maybe the cat is clogged? OBD-I so the O2 sensor is in front of the cat, so no codes if it was clogged.

Any help would be appreciated guys.
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post #2 of (permalink) Old 01-13-2004, 03:28 PM
 
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Re: \'90 S10 with 4.3L won\'t run correctly

how about the fuel pump. sometimes the pump will only be a lb. or two below spec, but still pumping and it will run drastically different. Every chevy we have owned has had to have the fuel pump replaced.
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post #3 of (permalink) Old 01-13-2004, 03:37 PM
 
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Re: \'90 S10 with 4.3L won\'t run correctly

I have a 93 S-10 Blazer and it began running rough after 2 weeks of owning it. Found a bad ground to the fuel pump was the culprit.

Good luck
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post #4 of (permalink) Old 01-13-2004, 06:16 PM
yv67warrior70
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Re: \'90 S10 with 4.3L won\'t run correctly

same thing happened to my 96' take out the thermostat and it ran better. but i still gotta do more to make sure tis the thermostat and not something else. [img]images/graemlins/AR15firing.gif[/img]
post #5 of (permalink) Old 01-13-2004, 09:34 PM Thread Starter
Mud in my Veins
 
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Re: \'90 S10 with 4.3L won\'t run correctly

Okay guys, writing these down and telling him soon.

Someone on another forum recommended the idle air circuit, but didn't specify anything beyond that. Anyone know what that is and what it does? Where is it on the TBI?
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post #6 of (permalink) Old 03-13-2004, 06:26 PM
crazy4offroading
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Re: \'90 S10 with 4.3L won\'t run correctly

heres a haynes scan
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post #7 of (permalink) Old 03-15-2004, 08:11 PM
wrobel
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Re: \'90 S10 with 4.3L won\'t run correctly

pull the egr valve off and clean any carbon deposits that might've built up in it
post #8 of (permalink) Old 03-17-2004, 11:45 AM
triplejracing
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Re: \'90 S10 with 4.3L won\'t run correctly

there could be a problem with the idle air circuit,my father had a similar problem with his 90 Z71,take a can of carb and choke cleaner with the engine running and spray around all the stuff on the intake,like all the vacuum lines and the base of the throttle body. If you hear a change in the rpm of the engine there's the leak.
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