Idle Issues..

[Galactica]

So I'm trying to get my new Galant all squared away and next on the list is this pesky idle. I tested the pins on the ISC and they're all reading around 29 ohms, which is apparently good. What happens is the car will fire up and idle pretty good, but it will sometimes drop idle and pick back up. Then when it's warm, I'll push in the clutch and the idle will usually drop to about 400-500 RPM's before coming back up. Sometimes it will drop to 1200 and then slowly drop down. If the AC is running and I push the clutch, the car will just die. If I turn the AC on in the driveway though, the RPM's will drop, but then pcik back up and the car will not die. Any thoughts as to a solution would be much appreciated. Thanks!!

 

[WaRrIoRs16]

Have you checked for vacuum leaks? If not, build or acquire a boost leak tester and check for leaks. The extra air being sucked in through the leaks will cause your idle to not behave properly.

Also if you haven't checked out your capacitors, please do so not only for the sake of your idle, but for the sake of the entire ECU itself. I can't remember which capacitor it is, but one of them sits right over top of a trace that leads to the ISC drivers. That capacitor has leak on both of the galant ECUs that I currently have and has fried the trace causing the ISC drivers on the ECU to blow.

 

[Galactica]

I'll have to see about getting a boost leak tester or building one. Not sure yet how to trace leaks with it though. I was told by the previous owner (946 on this site) that the caps were all replaced when hey had the KeyDiver chip installed. I didn't look at the ECU though because I trust what he said is true.

 

[WaRrIoRs16]

Hopefully you have a boost gauge installed correctly. Vfaq has a guide on how to build one in the intake section. Then all you do is put the tester on the inlet to the turbo and pressurize the system. Typically 15 to 20psi should find any vacuum leaks you may have. If you are boosting over 15psi, you might go a little higher to find any high boost leaks. I try to go at least 5 psi over my target boost level.

Once you start pressurizing the system, just go through with a spray bottle with a pinch of soap in it and spray your throttle body gaskets, injector seals, intake manifold gasket, and every vacuum line you can find. Those are the common vacuum leaks that can cause idle issues. Also make sure you listen for any leaks. The throttle body shaft seals have leaked on every 4g63t that I have seen, and that is also a vacuum leak. Check the intercooler piping and gaskets for other boost leaks as well.

 

[Galactica]

Awesome. Thanks man. And no, I do not have a boost gauge. The car is stock as a rock mostly. Just have the cute boost light in the dash. One thing at a time.

 

[AnotherNewb]

The boost gauge in the dash is based off of the maf not physical boost. You need a mechanical boost gauge to accurately know how much pressure your turbo is pushing as well as when you do a boost leak test.

 

[Galactica]

Yeah judging by its erratic pattern from having owned several other turbocharged cars WITH a proper boost gauge, I figured it probably wasn't reading actual pressure or it was malfunctioning. I'm just going to tackle these minor issues one at a time until she's perfect and then wait for the next thing to go wrong. Always does... Anyone have any pictures of a boost leak setup or how precisely to build one? Seems like I would need some 2" PVC with a cap and a air hose fitting on the end plus a rubber gasket to hook it all up, but it would be good to check some pictures.

 

[Okayplayer]

This one works fine.
click
but instead of a valve stem, I would throw a nipple on it and have a long piece of tubing attached to it that goes to an air nozzle.