Why does my engine run rich?

Tiny
SAL OZGON
  • MEMBER
  • 2002 CHEVROLET S-10
  • 107,000 MILES
It runs rich onboth banks 4.3Litre. It has a service engine light on and sometimes it misfiers.
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Friday, December 28th, 2012 AT 7:24 PM

52 Replies

Tiny
DOCFIXIT
  • EXPERT
Have codes read then post will advise this guide can help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back.
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Friday, December 28th, 2012 AT 7:45 PM
Tiny
SAL OZGON
  • MEMBER
Po172 and po175 and po300
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Friday, December 28th, 2012 AT 8:31 PM
Tiny
DOCFIXIT
  • EXPERT
P0300 needs to be solved first Random Missfire try this clean MAF check for any cracked or disconnected vacumn hoses. Recent repairs?
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Friday, December 28th, 2012 AT 8:57 PM
Tiny
SAL OZGON
  • MEMBER
It was the MAF sensor thank you so much
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Friday, December 28th, 2012 AT 9:40 PM
Tiny
SAL OZGON
  • MEMBER
  • 2002 CHEVROLET S-10
  • 106,000 MILES
I have a S10 pick with a 4.3L runs rich on both banks does have service engine light on.
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
DRCRANKNWRENCH
  • MEMBER
There may be a leak in the exaust near the oxygen sensors making it think it is running lean so it is dumping extra fuel cauising the rich situation. Look ofr exhaust leaks or the pressure regulator may be bad. Have the fuel pressure checked.
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
DIMIXBIKES
  • MEMBER
  • 1995 CHEVROLET S-10
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 161,000 MILES
Hello,

I have a 95 S10 2.2L automatic. I've owend this truck for about 2 years and have sense done numerous amounts of work to it. Shortly after I purchased the truck I discovered it had a blown head gasket and had the head checked, milled, added new seals, etc. Ever since i've owned this truck it had odd idel problems or acceration problems. I've change the plugs/ wires/ vaccum hoses, etc. Numerous times. I've also installed a new egr valve about 1 year ago. In the past the truck seemed to downshift sporadically at different speeds, however that seemed to clear up after I installed some new vaccum lines. I've also installed a new feul filter & feul pump. Now the truck is hard to start. It will take several seconds to crank and normally needs to be assited with pumping the throttle. Once it starts will will idel ok at times, then it will suddenly change its idel and accerate alittle higher with a low end bog. Or a bog at and speed when accerating. To cure this problem i've attempted to replace the throttle position sensor (twice now) and also the crank sensor. With little results. Also, when I start the truck it will blow feul out the tailpipe. What could be the source of this truck running rich with a low end bog?

Any ideas or suggestions would be greatly apperciated. Thanks -Jimmy
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
HMAC300
  • EXPERT
Chekc your fuel pressure, your regulator may be screwing up. It's condensation coming out your tailpipe, not fuel. It could also be the injectors, that's why you should have apro check it out to save yourself some cash on all the parts you've put in to try to fix it and it hasn't. Don't go buying the store bought injector cleaner it doesn't work
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
HAWGPOUND
  • MEMBER
  • 1994 CHEVROLET S-10
Engine Performance problem
1994 Chevy S-10 6 cyl Four Wheel Drive Automatic

what can cause the pass, side 0f a 4.3 vortec to foul and it is only the passenger side and you can smell that it is runnig way to rich
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
BILLYMAC
  • EXPERT
Hi sounds like leaky poppett valves this is the fuel injector unit under the plantum the orings go bad and cause eng flooding. Cost about two hundred parts and a cpl hours labor. However codes should be pulled and exact cyl misfire idenified billymac good luck
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
BILLZ24MAN
  • MEMBER
  • 1993 CHEVROLET S-10
  • 6 CYL
  • 2WD
  • MANUAL
  • 142,000 MILES
My truck wont pass smog, and I was wondering what causes a 2.8L to run rich. Please help
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
RASMATAZ
  • EXPERT
A bad O2 sensor, excessive fuel pressure (bad fuel pressure regulator or plugged return line), leaky fuel injectors, dirty air filter or restricted air inlet, or a defective coolant sensor that prevents the engine management system from going into closed loop mode
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Friday, January 22nd, 2021 AT 11:06 AM (Merged)
Tiny
DOZER202
  • MEMBER
  • 1991 CHEVROLET S-10
  • 4 CYL
  • 2WD
  • MANUAL
  • 278,000 MILES
2.5 vin code E running very rich. I replaced the oxygen sensor, coolant temperature sensor, map sensor and air sensor in the intake manifold. I can unplug three sensors and make it go into open loop and it runs good, but fuel economy suffers. The tailpipe is shooting out black smoke indicating the running rich. Any help is appreciated.
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
HMAC300
  • EXPERT
Read your engine code to see what has messed up on it. But because you disconnected sensors you have to start over. Pull the ECM fuse for thirty seconds then start truck and let light come on. Shut engine off and take a paper clip and cross a and b at the aldl. Count the flashes then come to the site here and look under diagnostic codes OBD1. Go from there.
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
MATTSCLINE
  • MEMBER
Did you ever figure this out? I have the same truck and the same problem. I did not know you can unplug three sensors and make it go back to open loop. So I will try that. I know the OBD trick but no code to read just 1, 2 flash.
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
KEN L
  • ADMIN
This sounds like a classic engine coolant temperature sensor that is causing he issue. Here is a guide to show you how to change the sensor out:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Please run down this guide and report back.

Cheers, Ken
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
MATTSCLINE
  • MEMBER
  • 1991 CHEVROLET S-10
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 98,000 MILES
Truck runs for a few minutes fine the starts to stutter and shut off. You can smell the unburned fuel and it acts like it runs rich and stalls out. Can start right back up and do it again. Not sure if the timing is when the IACV closes or just the computer kicking into †closed loop†(if I got that right). Pretty much all sensors and distributor changed.
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
ROL*S.
  • EXPERT
Hi Matt, were you able to see if it has any codes? I saw your other post and unplugging sensors usually does not reset codes, but disconnecting battery will.
And able to get fuel pressure?
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
MATTSCLINE
  • MEMBER
No codes and yes fuel pressure.
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)
Tiny
ROL*S.
  • EXPERT
Sorry Matt, I should have been more specific about fuel pressure and asked if a pressure gauge was ever installed to see how much pressure it has. Spec is 9-13lbs. higher pressure will make it run rich. It kind of sounds like the pump could be getting hot too.
And when you have a pressure gauge hooked up with the engine running, and the fuel pump is producing pressure within specification, let it run until the engine starts stuttering and stalling, to make sure the fuel pump pressure remains stable and within the 9-13lb. spec.,as it stutters and stalls.
And usually the check engine light turns on when they start running bad.
Also, it probably will have a code if you check it right after it stalls.
You need to make sure the vacuum lines are good. Did you guys change the MAP senor too?
https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method
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Friday, January 22nd, 2021 AT 11:07 AM (Merged)

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