idle surge

[honda4life]

So lets see this is my first real post and i hope i dont mess up to bad. i got a question here and im hoping you guys could help. my brother just bought a 1991 eagle talon today and the only thing wrong is wat i m being told is idle surge. when he and i turn the car on it's revs up to 3000 rpm and then goes down to 1000 and then it jumps up and down between 1000 and 1500 rpm. i was told to adjust the bliss screw in the throttle body but i wanted to get another opinion from someone who i trust. and after reading different post i think you guys kno wat u are talking about... any sugestions or comments??

[03tarmacblack]

Does it still do it after to warms up? If not i believe its the idle position sensor or something, the one that helps the car warm up on cold starts.

[honda4life]

no it does it all the time... he had it out and was driving it all day...

[sfd]

i dunno the mechanics of the DSM motor but usual things to look at would be plugs/wires/TPS/IAC. hell, i had an idle surge (but reverse, id lose power) because of a loose alternator belt.

[awdlaserbeam]

check for vaccum leaks, it could be several different things.

vfaq

or i found this one as weel
http://www.dsm.org/how-tos/tttt/tttt3.html

[2point4DSM]

My brother just bought a 1991 eagle talon today and the only thing wrong is what i m being told is idle surge. when he and i turn the car on it's revs up to 3000 rpm and then goes down to 1000 and then it jumps up and down between 1000 and 1500 rpm. i was told to adjust the BISS screw on the throttle body but i wanted to get another opinion.

Idle surge if very common with older DSMs and it can be caused by many things. Here a few....

1. ISC (Idle Speed Controller) - located on the throttlebody. Needs to be replaced when it gets clogged or the coils in the unit burn up. Basically, this unit controls the amount of airflow going to the motor when the throttle plate is closed. Test the ISC motor according to the manual or the link mentioned above.

2. Air leaks btw the MAF and motor - includes intake manifold gasket failure, numerous possible throttlebody leaks, IC pipe leaks, improperly routed BOV, ripped intake hose, leaky IC. Perform a leak test.

3. Throttle cable attached too tight. There needs to be some slack in the throttle cable so when the motor warms the cable doesn't yank on the throttle plate.

4. BISS

[eviltalon]

i had the same problem and it was my idle screw in the throttle body, but u might need to replace your idle speed controller.

[StealthTC]

ISC- Idle Speed Controller

Pretty much a common issue with DSM's I think I have replaced one in every DSM I have owned

[honda4life]

ok so i posted before asking about how to fix my brothers idle surge on his 91 talon n/t. well i took a look at the BISS screw and that didnt work, i checked for vacume leaks and there were none. so i got a new TPS sensor, that didnt work, then i got a new air flow meter thinking that might be it, again that didnt work. the only other thing i could of was there was maybe a problem with the ECU so i went and got a new ECU, and yet again that wasnt the problem. so just for fun i went and took off the metal cover over the exaust manifold and found that there are 2 small cracks in it. plan on going tomorrow to get a new mani but im thinking is it possible that that could be the reason behind the idle surge???

[awdlaserbeam]

Negative. The new parts you swapped in, where they New or used.

[2point4DSM]

Did you check #1 and #3 in my post above? And do you have a logger? To me it seemed like a waste of time swapping out the TPS.

[honda4life]

the parts we put in were new....

[honda4life]

i checked the cable but im going to go get a new ISC now and gonna see if the works... that was the only part i didnt get...