Miss under load when engine goes closed loop

Tiny
UNCLEJUNK70
  • MEMBER
  • 1994 PONTIAC SUNBIRD
  • 3.1L
  • 6 CYL
  • 2WD
  • MANUAL
  • 165,000 MILES
Car runs fine in open loop. As soon as the engine goes closed loop, there is a noticeable stuttering miss under load. New coils and ignition module. New plugs, wires, and crank sensor. Closed loop symptoms make me believe that the PCM is driving a too-lean or too-rich condition. No OBD-I codes at all. This issue is almost identical to one listed in a thread started by a member EK2000D back in December 2013 on his aunt's 1995 Pontiac. I've troubleshot every sensor on the engine and everything looks good. I'd be curious what solved EK2000D's problem (if it did get resolved). Thanks
Monday, February 4th, 2019 AT 7:36 AM

1 Reply

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

Misfires can be frustrating to track down, but this sounds like it could be a problem with a vacuum line somewhere. Here is a helpful link that should help you out.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

I have also included some step by step instructions below for you as well

Alex,
2CarPros
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Monday, February 4th, 2019 AT 9:55 PM

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