1988 V6 Running Rich / Rough Idle

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1988 V6 Running Rich / Rough Idle

January 31, 2025, 03:35:21 PM

over the past few months my V6 has been getting noticeably worse MPG and is harder to start up when warm
(it always starts up when it's warm but it'll take a couple tries)

on a cold start it fires right up and runs good until it gets warmed up

I've checked all over for vacuum leaks and can't find any, I've also sprayed brake clean on every vacuum line and around the intake but none made a difference

I checked the fuel pressure with the vac line on and off the FPR and it's in spec and I don't smell gas from the FPR vac line

tested the coolant temp sensor resistance when it's cold and hot and it's in spec as well

would a partially stuck open EGR cause it to run rich and idle rough?

I don't believe the 88 V6 has an air temp sensor so I'm not sure what else to check that would cause this other than the ECU possibly going bad

Re: 1988 V6 Running Rich / Rough Idle

Reply #1 – January 31, 2025, 06:17:56 PM

No codes?
Since you checked so many other things already i would check for possible failing TFI module since you have problem with warm start up.

Re: 1988 V6 Running Rich / Rough Idle

Reply #2 – February 01, 2025, 12:07:32 AM

Quote from: Ductape91 – on January 31, 2025, 06:17:56 PM

No codes?
Since you checked so many other things already i would check for possible failing TFI module since you have problem with warm start up.

That’s a possibility but that wouldn’t explain why my MPGs are getting worse and why it’s running rich

It’s always started for me warm and it’s never died on me so I don’t suspect it’s the TFI

Re: 1988 V6 Running Rich / Rough Idle

Reply #3 – February 01, 2025, 09:08:31 AM

The ECU is probably the last thing on the list to worry about.

How old is the O2 sensor? When was the last tune-up?