Wont hold idle after car is hot

[derder87]

I recently finished my 93 Talon tsi awd and it starts right up and runs fine. When the car gets hot it no longer wants to hold idle. If i start to slow down it will die. Whats weird to me is it only happens when its hot. Any advice or help would be great.

 

[eclipsyco]

If you give it gas will still die? Check The ISC may is out of range or is dead? Is the CEL on?

 

[blakkat]

Most cars run closed loop when warm at idle meaning they adjust afr using the o2 sensor, make sure yours is working properly

 

[derder87]

When i give it gas it will stay running. but if i take it out of gear and try to slow down it dies. it restarts by pushing in the clutch and putting it in gear just fine. but after its warmed up it wont stay started in neutral without gas. I re did all the vacuum lines to go with the new fmic and bov that i got. i used a diagram that i got from this forum. It hits boost just fine, i dont have any other problems as long as my foot is on t
he gas

 

[blakkat]

Sounds like an Isc to me. That's where you should check first. It idles when your on the accelerator because your allowing air in, if the Isc is ####ed it won't be able to allow enough air in for it to idle

 

[dsmracing92]

Agreed sounds like an ISC to me also!

 

[2ndGen]

man we all have so many idling problems with these cars :/ when mine started to do that I let it warm up then quickly took the battery out and removed the air intake house and took the isc motor out (without burning yourself like I did) and had a friend turn the key to on (engine NOT cranking and not running) and I held it in my hand and looked at the plunger. It would shutter and shake and not extend and retract. After getting a new one and doing the same test the plunger would extend and retract like normal. That's how I knew my old one was crap. Also your O2 sensor could be bad because it needs to heat up to start sending signals to your ecu. I ran mine un plugged and it would idle somewhat better before I replaced the isc but it ran rich and messed up my cat. Lol so don't do what I did thinking it was "helping". Get a haynes or research how to test the o2 sensor when its warmed up. Cant find my haynes manual right now otherwise I would tell you.

 

[codeofdastreets]

yeah defenity is a isc problem, I deleted mine, start ups are a pain but once its warm it runs perfect with no problems

 

[TalonsThree]

I am having a similar problem with my 92 TSi.

It starts fine, and I can drive/rev it all day without issue, but the second I let off the gas, the revs drop to zero and of course it stalls out.

Is this an ISC issue, or Idle Switch (or is that the same thing)?

Sorry for the probably really basic question, I'm a total engine newb but want to start turning the wrench on my Talons myself.

 

[JusMX141]

ISC probably has a dead coil. Same thing happened to the girlfriend's car about a year ago- new (used) ISC fixed the problem.

 

[TalonsThree]

Thanks Jus.. is it a relatively simple replacement? From what I've researched it's not hard at all (but wtf do I know)?

Also, can you ballpark what the cost is? I've read around $100 for a new one?

 

[JusMX141]

Step #1 would be to test yours and verify that it indeed has a dead coil so you're not just throwing parts at the car and hoping it fixes the problem.

[ame=http://www.youtube.com/watch?v=KibYz21IMA0]DSM ISC motor testing & Replacement - YouTube[/ame]


If you need a new one, the Standard part number is AC146; definitely $100ish.

 

[Boostdriven]

I looked at your mod list but you have nothing in there so I'm going to do some guess work here like number of other people said its possible that its your idle air controller (iac) so pull it out and test it like Justin showed you in that video. If it checks out ok there are few things that you can check.

Whatever you did to your car when you said you finished it, did you remove the hose that goes from your intake manifold to the pcv valve on your valve cover? If you did and capped off the nipple on the intake manifold then you just took away a small air supply to your engine at idle. If you didn't do that then check your pcv valve to make sure its not plugged up or stuck closed.

On factory set up that hose is used for removing crank case pressure (blow by) for emission reasons. While in boost the pcv valves holds boost from entering crank case but when your engine is in vacuum it pulls air out of the crank case. The other nipple on the valve cover between the two cams runs a hose to your intake pipe before the turbo, that bleeds off the crank case pressure while your car is in boost.

In reality you should take that pcv valve out and replace it with a regular nipple type fitting and run a hose from it to a catch can for best crank case ventilation. Stock set up just shuts that hole off when in boost and makes it useless, anyways back to the topic.

Another thing you need to check is your biss screw in the throttle body. If you removed that hose from the manifold you will need to compensate for that lost air with something so the biss screw will usually do the job. It's possible that your iac is maxed out and can not keep up with the demand of the engine to keep it running at idle. So check your biss screw and make sure its not all the way tight, try unscrewing it out and see if it will keep your car idling.

Another thing you need to check is make sure you have set you base timing correctly to 5 degrees, if your timing is to retarded your car will still run ok with part throttle but it will have hard time idling especially if there are other minor factors involved like the things I described above.

Anyways check those few things and hopefully you get it figured out, if not let us know and we will go from there.

Shit just realised that we are like 3 months to late to answering your question, hopefully you got it figured out. Hopefully this will help those who have similar problems in the future.

 

[TalonsThree]

A *HUGE* thank you to everyone above that posted with their help.

After driving for too long with my foot constantly on the gas to avoid stalling, I did everything as suggested (tested the ISC - found it was faulty, then replaced) and it was surprisingly easy with all of your help.

Thanks to a few posts on other threads on this forum, I ordered the part from Rock Auto for $70 as opposed to the $400 the dealer wanted for it. I then had that new part installed in 45 minutes, as opposed to the "minimum" 2 hours of shop time I was quoted.

I know for real gearheads this is a 2 second repair, but other than changing oil or filters, this was my first time working on my own car. It saved me over $500.

Guys, again - Thanks a ton.

 

[maxharmony537]

buy some seafoam or you can use water, pour some in your oil filler and and start the car and spray it down the intake (after MAF). it will make a lot of smoke, but the seafoam or water will break up and make all the carbon sponge like. you will need to change your oil after you put a few miles on it. if that doesnt work you can try throttle body cleaner that is sensor safe