Stumbling with no check engine light?

91,569 MILES • 1.8L • 4 CYL • 2WD • AUTOMATIC
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BRANDEN PAINE
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  • 4 POSTS
I had codes for random multiple misfires, overheat head protection, then each cylinder individually, misfire1,2,3,4 etc. I put 4 new coil packs in the car and deleted the DTC and it hasn't come back on, idles fine, but when I try to accelerate it starts stumbling like its misfiring, I also checked all the vacuum lines, didn't see anything broken, disconnected or otherwise. I have an Ancel fx2000 scanner, nothing great but it does do some system tests and can read more than just obd codes, it has 48 "Modules" that it can read if you need to know fuel trim, or pedal position etc. Please Help! Thanks in advance!
Nov 27, 2024 at 10:22 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,542 POSTS
It sounds like the catalytic converter is clogged up, if you check the LTFT values (e.g., +15% or more) could suggest the engine is compensating for the restricted airflow by adding more fuel.

Here is a guide to help you see if the cat is the problem:

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

You may need to remove the cat for a physical inspection. This can also be because of a lack of fuel pressure. also, I have seen the fuel pressure sensor cause this problem but usually there is a code for it. If when you rev up the engine and it starts to stumble, spray starting fluid into the intake to see if the engine changes. This can help determine if the problem is fuel or not.

Here is a guide to help check the fuel pump as well:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Fuel Pressure
Engine running - 2.5L 350–415 kPa
Key ON Engine OFF (KOEO) 350–415 kPa

Here are the instructions for your car. 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. You can rent a fuel pressure gauge at the auto parts store for cheap or free.
Nov 28, 2024 at 4:34 AM
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