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Running rich?

Tiny
BUSINESSFRED
  • MEMBER
  • 2006 ACURA TSX
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 225,000 MILES
I've been dealing with a rough and low idle when stopped in Drive.

I have short term fuel trims ranging from (-10% to -15%) while in drive

So far I've adjusted the Valves lash, Installed New Spark Plugs, New Timing Chain and Tensioner, New Water Pump and New Head Gasket with Resurfacing of cylinder head before installing.

Are there any diagnostic instructions for this issue you can provide me with? I'm considering replacing the ECT Sensor or MAP sensor.
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Sunday, July 28th, 2024 AT 7:09 PM

13 Replies

Tiny
BUSINESSFRED
  • MEMBER
  • 79 POSTS
I've added 4 pictures of current values on my OBD2 scanner in case any irregularities are found on your end, thank you.
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Sunday, July 28th, 2024 AT 7:55 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,512 POSTS
When you replaced the spark plugs were they black? Because these numbers are for a rich mixture, The MAP sensor reading can be off which will cause this.

Here is the location of the MAP sensor so you can swap it out to see if the readings change.

Also check the O ring seal for the sensor as well.
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Monday, July 29th, 2024 AT 10:48 AM
Tiny
BUSINESSFRED
  • MEMBER
  • 79 POSTS
When I pulled the plugs, they were white and didn't smell of gasoline. Forgot to mention I also have a slightly extended crank when starting the car

My understanding was that negative fuel trim values = running rich.

I will run the recommended fuel pressure test first, then if it checks out I will replace the MAP sensor thank you, will keep you updated.
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Monday, July 29th, 2024 AT 6:28 PM
Tiny
KEN L
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You are correct, negative numbers mean rich mixture, can I ask if all of the spark plugs looked the same? I would check out the MAP sensor.
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Tuesday, July 30th, 2024 AT 9:44 AM
Tiny
BUSINESSFRED
  • MEMBER
  • 79 POSTS
Yes, the spark plugs all looked the same. Okay, I will start with the MAP.

Is there any way to test the injectors for leakage?
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Tuesday, July 30th, 2024 AT 11:14 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,512 POSTS
Yep, here is a guide to help with that, but since they all looked the same I don't think they are a problem but you never know.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Check out the images (below). Please let us know what happens.

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Tuesday, July 30th, 2024 AT 1:10 PM
Tiny
BUSINESSFRED
  • MEMBER
  • 79 POSTS
I replaced the map sensor and the fuel trim values went to 0% momentarily before going negative again.

I will recheck my valve lash to confirm my exhaust and intake valves are within spec.
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Tuesday, July 30th, 2024 AT 9:14 PM
Tiny
KEN L
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Do you have exhaust leaks? If the exhaust system is pulling air the PCM will richen the mixture. If not you may have a bad PCM.
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Wednesday, July 31st, 2024 AT 10:08 AM
Tiny
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  • MEMBER
  • 79 POSTS
I readjusted the valve lash and retightened the exhaust manifold.

When I drive and let off the gas my fuel trims reach (-16.4%).

Could the evap purge valve also be a suspect?

If my timing were a tooth or half a tooth off would that also cause a rich condition?
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Wednesday, July 31st, 2024 AT 1:18 PM
Tiny
KEN L
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Yes, the valve can cause a rich condition here is the location so you can check it out, remove it and see if you can blow through it, if so, the valve is bad. Yes, if the timing of your engine is a tooth or half a tooth off, it can indeed cause a rich condition. Check out the images (below). Let us know how it goes.
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Wednesday, July 31st, 2024 AT 5:59 PM
Tiny
BUSINESSFRED
  • MEMBER
  • 79 POSTS
I plugged the vacuum line that comes from intake to the evap purge valve, and the car was running lean for the first time in a while but after a while my long-term trims reached negative again

Letting off the gas on acceleration the negative values tanked to (-12.9%)STFT, (-7.0%) LTFT

Although improved I am Considering replacing my ignition coils to remedy the misfiring type of idle while stopped.

I also noticed my exhaust tail pipe is sucking instead of blowing out exhaust.
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Thursday, August 1st, 2024 AT 12:22 PM
Tiny
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The issue was resolved, crankshaft was a tooth off.

Valve lash adjusted and smoothed out well, ran perfectly again.
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Thursday, August 8th, 2024 AT 2:21 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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That will do it, good find, glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.
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Thursday, August 8th, 2024 AT 10:14 AM

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