2003 GMC ENVOY ROUGH IDLE

  • Tiny
  • kslusher1
  • 2003 GMC Envoy

Engine Performance problem
2003 GMC Envoy V8 Four Wheel Drive Automatic 81000 miles

I keep getting a P0171 (system too lean) code. I changed the wires, plugs and fuel filter. It idles real rough in the morning. After it warms up and I drive 5-10 miles or so then everything runs fine. Could it be the O2 sensors? The MAF sensor is reading 3.49 on my scanner which I believe is normal.

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Wednesday, October 29th, 2008 AT 7:50 PM

5 Replies

  • Tiny
  • James W.
  • Member

If you have to crank it quite a few times to start it cold, check the cold start injector. If this isn't working, it will run rough until it warms up.

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Wednesday, October 29th, 2008 AT 9:45 PM
  • Tiny
  • kslusher1
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I checked the codes again and I had 4. 2 lean codes for bank 1 and 2 for bank 2. It cranks and starts fine. It just runs bad after it starts.

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Wednesday, October 29th, 2008 AT 10:03 PM
  • Tiny
  • James W.
  • Member

Sounds to me like the engine temp sensor is telling the computer that the engine is warmer than it is on startup. Thus, giving the motor too lean a mixture until the actual motor temp catches up with the sensor reading and then everything is ok.

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Thursday, October 30th, 2008 AT 11:54 AM
  • Tiny
  • kslusher1
  • Member

The engine coolant temp sensor?

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Thursday, October 30th, 2008 AT 11:00 PM
  • Tiny
  • kslusher1
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On my scanner it is showing the ECT and the IAT at about 20-30 degrees difference. Is the IAT sensor and the MAF sensor one unit on a 2003 envoy xl with a 5.3? Mitchell 1 online manual is only showing the 4.2.

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Friday, October 31st, 2008 AT 5:02 PM

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