Engine stutter

Tiny
RUNWAY7
  • MEMBER
  • 2001 BUICK LESABRE
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 156,000 MILES
The engine runs normal when it is cold but hesitates and stutters when it warms and runs off the sensor inputs.
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Monday, May 27th, 2019 AT 8:35 AM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon.

Runs off sensor inputs? The engine does that 100% of the time. Please explain.

How old are the plugs and wires? Basic tune up is where I would start.

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

Roy
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Monday, May 27th, 2019 AT 12:43 PM
Tiny
RUNWAY7
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Thanks Roy. The plugs and wires were replaced in the last sixty days. I just found out the computer has logged EGR codes p0404 and p0405. It has also logged a random misfire code p0300 that the EGR valve might cause. I believe my problem is a lean fuel mixture and I know now that the EGR circuit needs attention. What I do not understand is why the engine runs good until it comes up to temperature. I had been under the impression it ran on internal computer mapping until it warmed up but I guess not. When I get the EGR problems solved I will see what that does for the car. Please add anything you like and thanks for responding.
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Monday, May 27th, 2019 AT 6:29 PM
Tiny
ASEMASTER6371
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Okay, remove the EGR and start the engine. You should have exhaust leak through the exhaust port and a loud sucking noise from a vacuum leak. It may even stall.

If both of them are there, replace the EGR.

Also, 300 code is a lean code but not the EGR. In most cases, it is low fuel pressure from a weak fuel pump.

Roy
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Monday, May 27th, 2019 AT 6:54 PM
Tiny
RUNWAY7
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Hi Roy. I removed the EGR valve and I can hear the loud sounds of the exhaust and the vacuum leak sucking noise. The two round ports are clean and free of debris. I will install a new EGR valve. I have a fuel pressure gauge and I checked the pressure at the fuel pressure regulator. It is 48 lbs key on engine off and 46 lbs with engine running. Speeding the motor up and down has no effect on the pressure. Do you think this is enough pressure for this car?
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Tuesday, May 28th, 2019 AT 4:11 PM
Tiny
ASEMASTER6371
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Okay, that is a problem.

Fuel System Pressure.

Key On Engine Off 53-59 psi.

You need a fuel pump.

Roy
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Tuesday, May 28th, 2019 AT 5:51 PM
Tiny
RUNWAY7
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Thanks Roy. I will get a new fuel pump on the car also. This will take a few days. Thanks again for all your help with my car.
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Wednesday, May 29th, 2019 AT 1:25 AM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Wednesday, May 29th, 2019 AT 5:01 PM

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