ISV and weird throttle/idle response with cold.

halik · 08-09-2009, 11:57 PM

edit: Rechecked the symptoms, 4 posts down

I've got an interesting problem on my 86 na. The whole top end was rebuilt and it starts and idles without issue.

When the car is cold, giving it some throttle from idle makes it stumble a bit in the 1000-1800 rpm range, once you hit 2K rpm it works fine and none of this happens when the car is nice and warm. Idea ideas what that could be?

V2Rocket_aka944 · 08-10-2009, 12:30 AM

this happens on my car when its really cold out (below 60F here lol), i figure its the catalyst needing to warm up..

halik · 08-10-2009, 01:01 AM

Quote:

Originally Posted by V2Rocket_aka944

this happens on my car when its really cold out (below 60F here lol), i figure its the catalyst needing to warm up..

Hmm can it be oxygen sensors going bad (ie the heating circuit)

halik · 08-10-2009, 04:06 PM

bump so here's what happens:

The car does start but the idle stumbles for a second or two, then the rpms shoot up to 1500 and come back down and sit steady at ~1000. If I give it full throttle from 1000rpm it nearly dies before shooting up. Any idea?

Can it be dirty/bad ISV?

elzergone · 08-10-2009, 04:46 PM

Could be a bad AFM?

Check this guy's video on a cool little tweak:

http://www.youtube.com/watch?v=-11J8...om=PL&index=17

SprintStar · 08-10-2009, 11:30 PM

Quote:

Originally Posted by V2Rocket_aka944

this happens on my car when its really cold out (below 60F here lol), i figure its the catalyst needing to warm up..

My '86 Turbo does the same but I don't think it's weather or catalyst or oxygen sensor related. Why? Becoz here in Singapore, it's hot all year round, my RoW car hasn't got a cat nor O2 sensor. I think it's to do with the cold start enrichment. Is the original poster running stock chips or aftermarket?

Sprint.

halik · 08-10-2009, 11:37 PM

Quote:

Originally Posted by SprintStar

My '86 Turbo does the same but I don't think it's weather or catalyst or oxygen sensor related. Why? Becoz here in Singapore, it's hot all year round, my RoW car hasn't got a cat nor O2 sensor. I think it's to do with the cold start enrichment. Is the original poster running stock chips or aftermarket?

Sprint.

Stock chip, I rebuilt the top end last summer along with ported head, newish valves etc. It runs and revs great when warmed up, it's only when it's cold it acts a little funny.

08-09-2009, 11:57 PM	#1
halik User Join Date: Jul 2008 Location: Ann Arbor, MI Posts: 324	ISV and weird throttle/idle response with cold. edit: Rechecked the symptoms, 4 posts down I've got an interesting problem on my 86 na. The whole top end was rebuilt and it starts and idles without issue. When the car is cold, giving it some throttle from idle makes it stumble a bit in the 1000-1800 rpm range, once you hit 2K rpm it works fine and none of this happens when the car is nice and warm. Idea ideas what that could be? Last edited by halik; 08-10-2009 at 04:09 PM.

08-10-2009, 04:06 PM	#4
halik User Join Date: Jul 2008 Location: Ann Arbor, MI Posts: 324	bump so here's what happens: The car does start but the idle stumbles for a second or two, then the rpms shoot up to 1500 and come back down and sit steady at ~1000. If I give it full throttle from 1000rpm it nearly dies before shooting up. Any idea? Can it be dirty/bad ISV?