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1989 GMC Jimmy Rough running, looses power under load. Smel

Tiny
4WD4ME
  • MEMBER
  • 1989 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 115,000 MILES
4.3 V6. Runs rough thru acceleration. Will idle well for a while and dies. Black smoke. It runs alot better than when I got it but still not right. What I have done. NEW cap, rotor, wires, plugs, rebuilt TBI, new MAP sensor, O2 sensor and installed a COMPLETE exhaust from manifolds back. Also removed gas tank and cleaned it, installed new fuel filter. Did a compression check and had 155 high and 148 low. Oil pressure is also good. When I first got the truck it smoked really bad (black) I got a code for O2 sensor. Since it runs better (kinda) I am not getting any more codes and "check engine" has not come back on.
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Tuesday, October 26th, 2010 AT 10:09 AM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Probable causes of an engine running rich are as follows:

1. Excessive fuel pressure can be cause by restricted fuel return line or defective fuel pressure regulator.
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.
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Tuesday, October 26th, 2010 AT 10:24 AM

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