Idle problem. What do you think?
Idle problem. What do you think? Just last week I started having an idle issue. When starting the car, hot or cold, after it's been sitting for about 1/2 an hour it takes a bit longer to crank and will die right away unless I give it gas. I have to hold it for a few seconds then slowly let off to keep it idling. Even then it will drop to around 200-300 before raising up to normal. When I put it in gear (auto) it will drop again for 1-2 secs before raising to normal. While driving it runs fine, but when I stop at a light it drops again. After driving for awhile it seems to clear up, and I don't have any issues. If I turn the car off and back on, it idles fine, but let it sit about 1/2 an hour and I have to go through it all over again.
No dash lights as of now and I've driven around 100 miles since this started.
No vacuum leaks.
Replaced IAT with a new unit.
Cleaned MAF
Checked for any melted or busted wires, non loose either that I can tell.
The only thing that was done prior to this was changing my alt to a KG3, but I drove about two weeks with no issues before this started. any ideas? Could the MAF just be bad and need replacing?
No dash lights as of now and I've driven around 100 miles since this started.
No vacuum leaks.
Replaced IAT with a new unit.
Cleaned MAF
Checked for any melted or busted wires, non loose either that I can tell.
The only thing that was done prior to this was changing my alt to a KG3, but I drove about two weeks with no issues before this started. any ideas? Could the MAF just be bad and need replacing?
Joined: Nov 2001
Posts: 34,631
Likes: 2,554
From: Schiller Park, ILL Member: #317
I would start by checking fuel pressure when the issue is occurring, and see how much/how long pressure is held in the rail after a key cycle without actually starting the engine.
On The Tree
Joined: Dec 2014
Posts: 131
Likes: 0
From: Mesa, AZ
Have you tried it with AC on and off to see if it makes a difference. Sometimes with a load on your engine will sputter initially and then rev back up to normal, sometimes a failing compressor put extra drag on the motor and makes the idle fluctuate more then usual. Might want to check your throttle position sensor too. it could be giving the computer faulty readings when letting off the gas making it nearly die.
Have you tried it with AC on and off to see if it makes a difference. Sometimes with a load on your engine will sputter initially and then rev back up to normal, sometimes a failing compressor put extra drag on the motor and makes the idle fluctuate more then usual. Might want to check your throttle position sensor too. it could be giving the computer faulty readings when letting off the gas making it nearly die.
Joined: Nov 2001
Posts: 34,631
Likes: 2,554
From: Schiller Park, ILL Member: #317
It is definitely a myth that these pumps either work completely or not at all. Like anything, there are shades of gray and the many threads on this issue are solid proof.
Again, I'd start with a fuel pressure test, during the conditions that present the issue. See what pressure you have during the poor idle, and then see how long it holds pressure after shutdown.
