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Running Rich on Both Fuel Trims?

Tiny
RALPHP1254
  • MEMBER
  • 2003 OLDSMOBILE ALERO
  • 3.4L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 191,800 MILES
This car is running super rich on both fuel trims. I have a screenshot of how everything is reading. We have replaced fuel injectors, the regulator, fuel pump, spark plugs and just about everything you can think of and it’s still running rich and smells bad from the exhaust. I either feel like it’s a PCM fault or a faulty sensor. Is there anything y’all would suggest looking at? The MAP is reading low as well.
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Saturday, November 9th, 2024 AT 6:10 AM

11 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Is it hot where you are? 102 degrees for the air intake? Anyway, the computer is trying to lean out the exhaust. I have seen a clogged catalytic converter cause this issue or bad fuel pressure regulator. Here is a guide to help you test the cat and I would remove the vacuum line from the regulator to see if raw fuel is present which means the regulator is bad.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

This guide can help you go over other rich conditions which you might not have thought of:

https://www.2carpros.com/articles/why-an-automotive-engine-will-run-rich

Here is the fuel pressure regulator location so you can check it out. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.
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Saturday, November 9th, 2024 AT 11:47 AM
Tiny
RALPHP1254
  • MEMBER
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It’s 65 degrees here. I just replaced the cat on it a month ago and a fuel pressure regulator was put on it a week ago. Still smells like fuel in the line when shut off. Running, you can’t smell it.
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Saturday, November 9th, 2024 AT 1:28 PM
Tiny
KEN L
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I am thinking you have a fuel injector that is stuck open or the EGVAP purge solenoid is stuck open. How does it run at idle? Can you upload a short video? One of the spark plugs will be washed clean and that will be the cylinder that needs to be replaced. Here is the EVAP solenoid so you can see if you can blow through it which you should not be able to. Also, the air intake temperature says it is 102? So that sensor is bad or the PCM is bad. Check out the images (below). Let us know how it goes.
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Sunday, November 10th, 2024 AT 8:57 AM
Tiny
RALPHP1254
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Here is a video of the idle. I can smell fuel around bank #1 around one of the injectors.
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Sunday, November 10th, 2024 AT 11:08 AM
Tiny
KEN L
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Thanks for the video, clean car BTW, did you remove the vacuum line from the fuel pressure regulator, you might have defective part. Also, did you check the EVAP valve?
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Monday, November 11th, 2024 AT 8:48 AM
Tiny
RALPHP1254
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Appreciate it. Yes, I have, and it smells like fuel. It’s from O'Reilly's so I may have gotten a defective part.
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Monday, November 11th, 2024 AT 11:11 AM
Tiny
KEN L
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I sounds like you found the problem. Let me know how it goes.
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Tuesday, November 12th, 2024 AT 10:50 AM
Tiny
RALPHP1254
  • MEMBER
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Okay, unfortunately, it didn’t fix it. I put a replacement regulator in and that didn’t solve it. The MAP sensor unplugged make the fuel trims straighten out. And the car runs smoothly. Driving it is painful when unplugged as its max pressure from the trans lines. MAF sensor really doesn’t do a difference. Any ideas?
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Sunday, November 24th, 2024 AT 4:41 PM
Tiny
KEN L
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I would replace the MAF sensor and the intake air temperature sensor. Then clear the codes, you may have a bad PCM if this doesn't fix it. Also, I would check the catalytic converter as well.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Here are the sensors locations. Check out the images (below). Please let us know what happens. Did you remove the spark plugs to see if one of them was black?
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Monday, November 25th, 2024 AT 9:22 AM
Tiny
RALPHP1254
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Catalytic converter is fine. The IAT sensor will be replaced and the MAF was just replaced the other day. I’m also going to replace the MAP as well.
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Monday, November 25th, 2024 AT 4:38 PM
Tiny
KEN L
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Sounds good, clear the codes after the job is completed and let me know :)
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Tuesday, November 26th, 2024 AT 10:35 AM

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