High Idle and surge

[n00btalon]

So i have quite a few problems with my 91 tsi. So heres one to start off with. Lately when i start the car (when its sat and is cold) It idles high till warmed up. But sometimes the idle will climb to about 2,000 and then it will fall down, like the car kicks it down and then it will climb up again and will kick it down. Its hard to explain it, but i do know that someone i know, their car was doing that when it was over heating. but i know thats obviously not the case here...

HELP!

 

[Rashwerd]

kindly sounds like idle surge?? id check the isc and tps i checked mine but all seem ok if i checked them right..theres a vfaq on it...also having my ecu checked as well..

 

[GVR4592]

It sounds like you're describing idle surge. It can be caused by a lot of different things and sometimes it's pretty difficult to diagnose. I would start by doing a boost leak test
http://vfaq.com/mods/ICtester.html

Then I would read this http://www.dsm.org/how-tos/tttt/tttt3.html

 

[n00btalon]

the turbo is crap still stock 14b (still boosts but has shaft play) could it have to do with most of my problems?? car does have 110,000miles

 

[jredgo1234]

Yeah use the vfaq link above or this http://www.dsmtuners.com/forums/showthread.php?t=54439 to understand more.

Also, i was having very weird idle problems and a few weeks later the caps in my ecu fried the whole thing. So, if you haven't replaced those you need to do that!!!!

 

[n00btalon]

thanks guys, i will be doing a boost leak test asap. and those articles are very helpful. anyone else is that has some .02? i am glad to listen haha... especially if u have expeirenced the same sort of situation!

 

[n00btalon]

So i took off the Isc and checked for wear and cleaned it up... it looked fine. But am still getting the problem. I saw someone posted with pretty much the exact same problem as me and said they fixed it by messing with the BISS screw?


should i mess with that?

 

[pedrick1]

the base idle set screw is usually only good to mess with to fine tune the idle, if its a major surge then the idle screw will only do so much. It isnt dangerous to mess around with but just to be safe you should count how many turns you turn it one way or another so you can go back to where it was previously set if need be

 

[nates6969]

first do a boost leak test, they can cause some serious idle surge...the biss screw is a common leak as well. if you do decide to tweak the biss screw, you really need to put the ecu into diagnostics mode and ground the timing wire. You can find tech articles on here on the exact process. Chances are though, the biss screw won't help you unless its a major vacuum leak but worth a try. I had the same problem on my 91 tsi...2000rpm idle when cold then as soon as it warmed up a few deg. the idle surge started...I believe mine was a bad FAIV (fast air idle valve). its a pain to replace as you have to replace the lower half of the throttle body. also you said you checked the ISC, did you actually test the resistance on the coils?

If you do decide to give up on fixing it and can deal with a 2000 rpm idle for the first few minutes of running, you can unplug the closed throttle switch on the throttle body (its the one wire harness plugged right above the throttle cable). with this unplugged this tells the ecu that you are not trying to idle and therefore it does not initiate fuel cut every time it revs up (the surge). It a good option if you just want the annoying surge gone. Try it out after you've done a boost leak test, it won't hurt anything or throw any codes

 

[n00btalon]

thanks for the info ill be checking it out tonight. btw i was just up in ontario weds an thurs. next time ill be looking for u! haha damn are their not any cops in canada?? people are nuts haha. i was in hamilton btw.

 

[matt1995tsi]

MY 91 TSI did the same thing and it was a bad idle air sensor you mite check that to see if its your problem?

 

[nates6969]

Hamilton huh, so you probably passed right by london then...and to answer your question, we definitely have cops...haha I know cause the other week I got busted doing 47km of the speed limit! a nice $277 ticket....then 3 days later got pulled over for taking a left turn too hard! come on! if you have awd you have to have fun with it!

 

[Tsi_User]

if none of those threads, look into "FIAV blockoff", your symptoms are exactly what i was experiencing and doing the blockoff fixed the problem.