ok well before i put in this new head, i had idle surge. I pretty much am sure that is being caused by a bad coil in the ISC. Well anyway, we got the new head put in yesterday, and it wanted to idle at like 3k rpm. but if we quick revved it a little, then it'd go back down to like 1k and do the idle surge like it used to. well the 3k idle started to happen more often, so we popped the hood and kinda pressed on the throttle spring thingy ma bob, and if we pressed it like closer to the lil switch that it hits when its at 0% throttle, it'd idle back to the normal range, but now its gone past that stage and just idles at 3k no matter what, and will slowely creep to like 3300rpm at long stop lights. any ideas? could it be that switch?

Throttle cable and TPS sensor adjusted correctly?

Could be the throttle position sensor. Or it could be that the rod that goes through the throttlebody and connects to the throttle position sensor has worn into the throttlebody creating a vacuum leak and possibly bad readings for the sensor. This was a common problem in older carbed cars.

i've never adjusted a tps before, it's in the same place its always been. if u know how to adjust it please tell me! the throttle cable is fine im sure. its not real tight, but at the same time, not loose. I've been doing all sorts of serches, and i found this site that's got some good info. imma go do some of the tests and see what happens. here's the link to the site if anyone else ever has problems like this.
http://www.geocities.com/MotorCity/Downs/7...8/dsmtests.html

If you didn't loosen the TPS bolts then it should be okay.

Sounds like the throttle cable is off like Ecoli said earlier. Adjust that so it sits against that stop when there is not pressure on the throttle.

hey thanx for the help, it WAS the throttle cable. it was ever so slighty too tight. but problem is fixed and i've never been so happy to hear that idle surge!!!

Hey guys, this is my first post. I own a 91 Galant VR4 and I am too having an idle surge problem. Mine happens whenever I press in the clutch. I will be driving and when I press in the clutch, it will rev to 4K rpm. This does it in any gear and it is making me MAD!!! I had installed a ACT 2100 this past summer, all caps replaced in my ECU, K&N filter, and I removed the wastegate selenoid. I hear it could be many things, ISC, FIAV, throttle body, or a warped flywheel. Any suggestions?

From everyone's good friend, Rick Shindley:

I worked on a '91 today that had bad idle surge. I checked the ISC
motor and cleaned the throttle body for starter. No affect.

I cleaned the BISS and checked its o-ring. No affect.

I removed the ISC motor and disassembled it. No problems found.

I reset the idle switch (throttle plate stop). No affect.

Finally, I removed the throttle body (again) and disassembled the
fast idle air valve. It was black with carbon. Rather than risk it
not working, I replaced the lower throttle body assy with one from
an old '95 throttle body (I didn't have a 1G TB lying around). It
worked!!! The FIAV was stuck open (apparently) and wouldn't close
when the coolant to the TB got hot.



Rick

i have an idle issue as well, and i have also checked the isc, adjusted the biss, etc. the car idles from 1100-650 every 5 secs or so when at a long stop. i have a 90 TB that i have been taking apart to look at and learn, but i don't see how you can get at the FIAV, unless its that spring thing behind the small metal plate held by 3 bolts? is there a way i can use the 90 lower assembly on my 91 TB?

but then again, it could be my hacked mas. hughes?

check the biss screw o ring. my friend had a surge because of it.