1995 Buick Lesabre engine stumbling

1995 BUICK LESABRE
160,000 MILES • 3.8L • V6 • FWD • AUTOMATIC
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DPLEMEL
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  • 1 POST
Engine stumbles on acceleration. Runs good on full acceleration @higher rpm. Engine light code is icm trouble. Replaced icm, coils, wires, plugs, fuel filter, throttle position module, cleaned maf, checked fuel pressure. What is left when nothing has helped.
Mar 23, 2015 at 11:58 AM
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KASEKENNY
  • ✓Experienced Mechanic
  • 18,907 POSTS
More than likely you have a vacuum leak. Basically the air fuel mixture is not correct so when you introduce more air, the engine stumbles as it is lean. Normally this would be a rich condition but if the fuel pressure is ok then we need to suspect the mixture is lean. Here are some guides that will help with this.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://youtu.be/4ktw1X4W_-k

https://www.2carpros.com/articles/engine-hesitates

Also, if you can tell us what the fuel pressure was when this was stumbling then that will help eliminate it.

We can also check the o2 sensor data while this is happening which will tell us if the engine is running lean.

Below is a guide that will give the detail on how to know what the short term fuel trims mean. Please let us know what questions you have.

Thanks
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Aug 2, 2021 at 1:19 PM
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