Any ideas why my idle will bounce from 1100 - 1300 continuously in a '90 200TQ?

andysprague · 03-02-2005, 09:08 AM

At start up it idles consistantly high till warm then it starts to bounce from 1100 - 1300 continously up & down. It does this 100% of the time.

I took off the ISV & cleaned it = nothing.

I unplugged the ISV = same bouncing.

Searching the archives hasn't really helped.

Anyone have any ideas?

Thanks!

Suffolk · 03-02-2005, 09:38 AM

Unmetered air leaks?
Clogged Fuel Injectors?
TPS?
-Scott by BOSTON

XcellR8edAudi · 03-02-2005, 09:47 AM

Jon Clay · 03-02-2005, 01:33 PM

I soldered mine up but it only lasted a day before they recracked. The new ones have a better design which doesn't lend themselves to cracking.

You could try unplugging the throttle switch and connecting a wire across (I think the bottom two pins) to see if that stabilizes the ISV. Also try cleaning the ISV out with some carb cleaner.

comp_jas · 03-03-2005, 03:57 AM

I wrote a lengthy post about this called "wild idle".

hdtrc · 03-05-2005, 10:15 AM

I was letting my '89 200QT idle for about 1/2 hour when it started doing the same thing. Aside from test trips around the block, the car hasn't been on the road since I got it for free 20 mos. ago. I rblt the head, had the exh manifold welded (Superior Welding...Pittbrg,PA)and a whole lot of suspension work. The interior gets wet after rains so I let it idle to dry out. Suddenly the idle started swinging from 1000 to 1300. I unplugged the TPS and the revs shot up,unplugged the fuel cutoff and it stabilized but very erratic, unplugged the ISV and nothing changed, ran the throttle bypass screw in and out but little changed, all new seals and gaskets, charged the battery, check alot of stuff. I'll let you know when I fix it.

03-02-2005, 09:38 AM	#2
Suffolk AudiWorld Super User Garage is empty, add now Join Date: Aug 2001 Posts: 2,760	Re: Any ideas why my idle will bounce from 1100 - 1300 continuously in a '90 200TQ? Unmetered air leaks? Clogged Fuel Injectors? TPS? -Scott by BOSTON __________________ THANKS to all who voted in this month's NAAClub.org's election. Learn history about the ACNA at http://www.acnasupport.com -Scott by BOSTON Driven: (like I had key on my key ring) 74 100LS, 80 4000S, 86/87 4000S/4000Q, 86 5000S, 90 200 Avant, 91 200 20V Avant & Sedan, 99 A4, 99 A6 Avant a few others and MANY rental cars. NHIS/NHMS, LimeRockPark, WatkinsGlen, MontTremblant, Poconos, VIR, MidOhio, AutoBahnCC - Full, Daytona

03-02-2005, 09:47 AM	#3
XcellR8edAudi AudiWorld Super User Garage is empty, add now Join Date: Dec 2002 Posts: 3,255	i would say tps... __________________ Current Rides: 2005 Subaru Impreza WRX STi 1987 Audi 5000 CS Turbo Quattro Past Rides: 1988 Audi 90 FWD/Auto 1988 Audi 5000CS TQ Avant 1989 Audi 200 TQ 1987 Audi 5000CS TQ Avant 1988 Audi 5000CS TQ 1995 Audi 90 Quattro 1990 Eagle Talon TSi 1992 Subaru Legacy L Wagon 1995 Ford Escort Wagon 1989 Volvo 240 DL 2005 Subaru Impreza 2.5RS

03-02-2005, 01:33 PM	#4
Jon Clay Junior Member Garage is empty, add now Join Date: Feb 2003 Posts: 615	agreed, probably the solder joints have cracked and you need a new one I soldered mine up but it only lasted a day before they recracked. The new ones have a better design which doesn't lend themselves to cracking. You could try unplugging the throttle switch and connecting a wire across (I think the bottom two pins) to see if that stabilizes the ISV. Also try cleaning the ISV out with some carb cleaner. __________________ <a href="http://filebox.vt.edu/users/jdubyk/Audi/Index.html"> </a> ______________________ AIM SCREEN NAME: j0n clay (that's a zero in j0n)

03-03-2005, 03:57 AM	#5
comp_jas AudiWorld Member Garage is empty, add now Join Date: Apr 2002 Posts: 590	Re: Your ISV has failed. I wrote a lengthy post about this called "wild idle". __________________ JAS '86 4000cs (RIP) '86 5000CS QT

03-05-2005, 10:15 AM	#6
hdtrc New Member Garage is empty, add now Join Date: Sep 2003 Posts: 53	Mine does the same thing I was letting my '89 200QT idle for about 1/2 hour when it started doing the same thing. Aside from test trips around the block, the car hasn't been on the road since I got it for free 20 mos. ago. I rblt the head, had the exh manifold welded (Superior Welding...Pittbrg,PA)and a whole lot of suspension work. The interior gets wet after rains so I let it idle to dry out. Suddenly the idle started swinging from 1000 to 1300. I unplugged the TPS and the revs shot up,unplugged the fuel cutoff and it stabilized but very erratic, unplugged the ISV and nothing changed, ran the throttle bypass screw in and out but little changed, all new seals and gaskets, charged the battery, check alot of stuff. I'll let you know when I fix it.

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