Mongoose350

iTrader: (1)

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?

wssix99

iTrader: (5)

What happens when you put the car in to Neutral at a stop?

Mongoose350

iTrader: (1)

Same as if in park. It will idle a bit higher than in drive. It still drops and stutters a bit before raising to normal.

RPM WS6

iTrader: (3)

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.

McGinnis

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.

Mongoose350

iTrader: (1)

Same with or without the ac being on. It will die right away from a cold start, but after that it will drop and stutter a bit before correcting itself. I primed the pump about 3-4 times this morning and I stayed running, but barly. It was bouncing from about 200 to 500rpm and kept it up until I gave it gas. I'm leaning toward fuel issue. Could this be a weak pump? I've always been told that fuel pumps don't mess up, they work or they don't. Regulator maybe?

RPM WS6

iTrader: (3)

You were told bad information then. Fuel pumps can and do get weak; sometimes the loss of pressure isn't even visible on a gauge until the engine is under load, so a simple idle PSI test isn't always enough (sometimes you need to tape the gauge to the windshield and watch what happens under load). Also there is a check valve that holds fuel in the line for quick starts, and this valve can go bad causing the need for several primes (or long cranking times) on a cold start.

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.