Running rich

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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Thursday, January 6th, 2011 AT 1:57 PM

3 Replies

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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Thursday, January 6th, 2011 AT 6:08 PM
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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Monday, July 2nd, 2018 AT 12:33 PM
Tiny
KEN
  • 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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Thursday, July 5th, 2018 AT 1:02 PM

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