Zoolander

iTrader: (8)

So my FD has been running "perfect" for almost three years...I've been able to just turn the key and drive. Last month, after a month of sitting, I fired it up and drove it about 45 miles to a car show with no issues. I took some spirited runs along the way but nothing super crazy. Pulling into the lot and parking, I did not notice anything wrong at all.

Six hours later upon leaving, the idle revs around 1800-2000k! So far I'm reading about vacuum leaks, TPS, ISC, waxrod, etc. I've driven it twice now since this happened and have noticed that it idles at 1800 when cold and an electrical load does not affect it. But once it's warmed up, the lights will affect the idle. Last night, it was high with the lights on, it went down to 1500 with only the parking lights on, and with the lights off, the idle hunts from low (almost stalling) to high. I didn't get the exact RPMs unfortunately.

Before I dive into this....can this be an electrical issue (and easy fix) besides a vacuum or air/fuel issue? I think I read the TPS was affected by electrical load so maybe the TPS just crapped out spontaneously. It's been three years since I've done any heavy duty mechanical stuff to the car so I'm out of practice...and I kind of gotten used to not working on it. Anyone with insight before I have to get my hands dirty again?

Thanks as always.

Pertinent info: I had the tie-wrapped silicone vacuum line job done years ago and a superficial visual inspection looks okay and it has a Pettite ECU.

thewird

iTrader: (8)

Vacuum leak. Find it, fix it, problem solved.

thewird

Nataphen

iTrader: (6)

Mine's just started doing weird stuff like this too, and I don't know that it's a vacuum leak. Whenever I turn the HVAC blower on, it starts idle hunting, but it doesn't do it every time and eventually it settles into stable idle for a second. Does yours ever settle and then start hunting again? Not trying to thread jack, it just sounds like a similar problem and I didn't want to start a new thread.

EDIT: I think it only does it when the AC button is pushed, not just the blower being on. I'll doublecheck tonight. I have no AC, I just push the button from time to time to turn the cooling fans on low. It doesn't idle hunt when the cooling fans come on at any other time.

Nataphen

iTrader: (6)

I just checked, it only idle hunts when I turn the AC button on. I can turn the lights on, rear defroster, any other electrics, the cooling fans and HVAC blower can be running at any speed, and the idle is perfect as long as I don't turn on the AC switch. The voltage stays between 13.3-13.8 at all times.

Zoolander

iTrader: (8)

Not what I wanted to hear at all. My boost is -16 at idle and it seems to be hitting full boost on full throttle. Does that mean anything? If an electrical current is affecting it then doesn't that point to a bad TPS or ISC? And can/do those things just spontaneously go bad?

No problem on the thread jack...the more eyes and brains the better. I too don't have AC but use it for fan control. I didn't think to check with the AC/fans running but will soon. Mine has not settled at 800....but it has at 1800 with the lights on and 1500 with just the parking lights on. It hunted and almost stalled once warm and the lights were cut off. I'll check with the AC and report back.

Thanks.

Dudemaaanownsanrx7

iTrader: (23)

Doesn't mean anything, a small leak can cause a big idle surge and will not majorly affect vacuum and will definitely not change your boost. Start the car and take some carb cleaner, spray it around different areas especially under the UIM. If you make it stumble you found a leak. Or you can use a pressure tester system, basically just need a plug that you can attach to your throttle body elbow that has a valve stem in it, then hook it up to an air compressor. Pretty easy to make with some imagination. (exhaust pipe, pvc, ect) Other things to try is check the throttle linkage, the dashpot, you could remove the warmup system to eliminate that as a possibility. The ISC can get dirty and/or just stop working completely but I doubt that's the problem, TPS usually does not go bad. You can check the ranges with a multimeter, a couple sewing needles makes it easier to test, if you dont have a PFC.

The main thing is to start checking things, it sounds like you already did the research but YOU have to do the leg work. Within an hour or so you should be able to figure out what the cause is. Fixing it will take longer, but first step is to diagnose the cause.