wierd idle surge

[badas93tsi]

My car just started doing this wierd idle surge b.s. The first time it did it, the engine was cold and i drove it like 7 miles and when I got to where I was going, it was idiling fine. Now its doing it even when its warmed completely up. I did a few searches and decided to unplug the isc while the car is surging to see if it stops, it didnt. Just for sh*ts and giggles I unplugged the mas, it idled fine. I had a friend loan me his mas and it surged with it too. I'm not sure what to do, I tested my isc with an ohm meter and got some irratic readings, but from what I read if it doesnt stop surging when you unplug it, its not bad. Please someone help, its annoying as hell.

 

[vintagemuscle]

Your Logger will tell you if your ISC motor is working.

the logger will not tell you if your isc is working properly. the isc is a stepper motor and doesn't send info back to the isc. the logger will just tell you what the isc should be doing. that is why the ecu doesn't throw a code and turn the CEL light on when the isc is bad.

 

[Turbo Talon 111]

i forgot to mention the IAC is supposed to make a noise when it comes on.

 

[badas93tsi]

I dont have to hold it to the floor, just about 3 or 4% until it warms up a little. To me that is a good trade off for have a severe idle surge. I drive my car maybe 4 or 5 times a month, so its not that big of a deal.

 

[Funk1]

I Have a 98 talon tsi, and am having a similar issue. But it would appear that it "might" be O2 sensor related. Here's why:

When I start my car up and it is open loop (cold) it idles fine. when the car starts to come up to temp, it starts to surge varying about 150-250 rpms. (naturally I would suspect the O2, because it has 60K on it.)

I have done some intake leak checks and I have some known leaks, one being in the TB shaft seals, the other being right at the fp regulator. (one of the little metal tubes in it is loose.) I just figured it would be ok.

But the coolant comment is one I hadn't thought about. I need to re check the coolant levels and see where they are...

Dunno where to go from there. I don't want to get into this "swap-tronics" mentality of chasing the problem.

Any one else have an O2 cause the surge?

 

[vintagemuscle]

I Have a 98 talon tsi, and am having a similar issue. But it would appear that it "might" be O2 sensor related. Here's why:

When I start my car up and it is open loop (cold) it idles fine. when the car starts to come up to temp, it starts to surge varying about 150-250 rpms. (naturally I would suspect the O2, because it has 60K on it.)

I have done some intake leak checks and I have some known leaks, one being in the TB shaft seals, the other being right at the fp regulator. (one of the little metal tubes in it is loose.) I just figured it would be ok.

But the coolant comment is one I hadn't thought about. I need to re check the coolant levels and see where they are...

Dunno where to go from there. I don't want to get into this "swap-tronics" mentality of chasing the problem.

Any one else have an O2 cause the surge?

you NEED to fix all boost leaks before you try convincing yourself that it is something else. once all leaks are fixed then you can move on to other possibilities. i'd bet that the tb shaft seals is your problem.

 

[Turbo Talon 111]

you NEED to fix all boost leaks before you try convincing yourself that it is something else. once all leaks are fixed then you can move on to other possibilities. i'd bet that the tb shaft seals is your problem.

that would be my guess to. after i fixed some leaks mine stopped surging when cold but would just idle high. then when i replaced the tb to get rid of all the leaks it worked fine.

 

[Funk1]

that would be my guess to. after i fixed some leaks mine stopped surging when cold but would just idle high. then when i replaced the tb to get rid of all the leaks it worked fine.

Cool, I guess I will look into that more first.

Thanks.

F

 

[SlowChild3]

I was reading somewhere that if your isc is bad then it might damage the ecu? I hope this isn't possible.

 

[badas93tsi]

Ive never heard that, it was just annoying and embarrassing. Im not even sure mine was bad, I think it was the fiav.

 

[Dragon Talon]

I have the same wierd idle surge, idle at about 1100 to 1250rpm.I have started to do several checks. Only two things I have come across that is strange..# 1 a ticking noise comes from my isc when the ignition is just turned on..But the resistance,(tested in ohms) was in good range.... #2 I checked the resistance of TPS when in working back and forth the TB, which was reading (550-4870) Meaning lower# with TB closed and higher# WOT.. But spec in manual is (1100-5600ohms) But I can not check the voltage reading...All these test are being performed by manual procedure.. These are just a couple of things I have tracked down...Any1 got input if my TPS is bad?

So what and how should you set your tps? Been thinking of just replaceing the whole TB.
This idle surge promblem is no fun. is this a promblem for n/t and turbo..??