recently started running rough and misfiring when cold?

117,000 MILES • V8 • 4WD • AUTOMATIC
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MIKE HANKS
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  • 1 POST
I have a 1999 Tahoe that recently started running rough and misfiring when cold. This problem goes away after about 10 miles of driving. The car idles well at all times, misfires under light throttle application, but goes away under heavy acceleration.
The car has been tuned up with new plugs, wires, distributor cap and rotor, and new fuel filter. The engine light is on and only one code is present: "Random Cylinder Misfire" (I don't remember the code number).

It seems like a fuel related problem to me, however, I am wondering about oxygen sensors, or possibly the Mass Airflow Sensor. Any ideas which direction I should go would be greatly appreciated.

Thanks!
Jan 3, 2008 at 9:16 AM
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SQM
  • ✓Experienced Mechanic
  • 6,383 POSTS
Hello,

The random misfire can be due to a number of components. It could be for a fuel issue as you are suspecting but it could also be due to a faulty EGR valve, cam sensor etc.

The best course of action would be to take a step-by-step approach to finding the reason.

Take a look at this helpful guide:

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

I have attached a trouble shooting guide for the random misfire below.
Follow those steps as it can help you determine the issue.

Please let me know if you have any questions.
Thank you.
Jan 15, 2022 at 4:27 AM
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