Weird idle problem and biss

[Dsmj89]

I couldn't find a thread that sounded similar to my problem so here it is.
About 2 days ago my car started to idle weird, no surging, just high idle. The car would idle, fully warmed up and driving, it would idle at 1200-1400 rpm, so today in the morning i adjusted my throttle cable and the idle fixed. Now tonight going home the car didn't idle that high but it started to idle at 900-1000 rpm and stay there. I got home and tried closing the biss screw some more, and to my surprise, it was closed all the way ! And the car's idle wouldn't drop.
I do have to change my water pump and thermostat, not sure if that has to do with my problem in any way ? Please any help is greatly appreciated guys.

 

[RT-AWD]

your isc motor maybe on the way out or, may be stuck in one position. look for boost/vaccum leaks by testing. also when you adjust the biss are you grounding out the isc cable using the grounding plug behind the battery.

 

[LiquidX]

Not sure if your TB was touched anytime, but how open is your throttle plate in the closed position? Could adjust the throttle stop to have it +/- open. May need to adjust your TPS then if you go that route which only takes a second to do. Hope that helps

 

[Dsmj89]

your isc motor maybe on the way out or, may be stuck in one position. look for boost/vaccum leaks by testing. also when you adjust the biss are you grounding out the isc cable using the grounding plug behind the battery.

No i didn't ground it out. Is this really necessary ? And how would i go about doing that ?

Not sure if your TB was touched anytime, but how open is your throttle plate in the closed position? Could adjust the throttle stop to have it +/- open. May need to adjust your TPS then if you go that route which only takes a second to do. Hope that helps

Not sure i'll have to check into that plate. Thanks.

 

[RT-AWD]

If its in the same spot as mine, its a rubber nub behind the battery uncover it and you will see a plug, plug your isc wire into this and then adjust the biss (with the car running). yes you need to do this or else the isc will just adjust to your changing the biss screw and nothing will change.

 

[DarkMyrakul]

i agree about adjusting the isc...but personally it sounds like your throttle plate is sticking open, from what you said about adjusting the throttle cable. a common problem if you haven't cleaned your tb in a while. if the whole isc thing doesn't work out then i would suggest cleaning the tb as the next option.

 

[Dsmj89]

Thanks guys will look into that monday on my day off. It gets annoying sometimes as it does it sometimes, and then at times it won't do it at all.

 

[Dsmj89]

Still nothing. Car doesn't do this all the time either. It does it when it wants to. I'm suspecting a vacuum leak, as last night when i got home from work the car was surging. Vac readings went from my normal 21 and going up and down to 25-26 and back up to 21, THAT'S TOO MUCH VAC !
What do you guys think ? Could a bad biss screw cause a vac leak to happen that bad ? Could it be something other than that ? I'm at total lost.

 

[black_gst]

sounds like a big vaccum leak... if you have a boost leak tester nows the time... mine would do the same thing when my intake gasket was bad

 

[Dsmj89]

Thanks. I totally forgot about the intake manifold gasket as well ! I bet that thing has never been changed. Will look into that as well, let's see what the boost leak tester discovers.

 

[92dsmgst]

shoot some carb cleaner on the intake gasket for a quick diagnosis. Dont get to happy thought, my car has pretty close to the same problem( 95' talon awd), it idles good cold but once its warm it idles up to 2000-2500 rpms, i replaced IAC, TPS, ECT and tons of other things. Let me know what fixes your problem because i am still looking for a solution :/

 

[jdodds]

Its sucking air somewhere. Get any boost leaks you have fixed, then check your ISC. Also, the o-rings on the BISS screw could be bad. Take it all the way out and youll see them.

 

[Dsmj89]

Jdodds i was thinking the same. I will be getting me a new biss screw kit tomorrow to see if that cures my problem. Then again it's a 15 year old part...