different idle surge

[gtbread77]

hey guys new to the dsm world so any help is appreciated. i have a 1990 talon tsi you can check out my mod list for mods, i have searched the vfaqs and none of the symptoms are the sam as im having.

so when i am at normal hwy rpm's 3k-4k everything is fine, as soon as i let off throttle the surge starts, between 1000-1500 rpm which is normal but where it gets weird is that it stops when i come to a complete stop. checked throttle body, no vac leaks, biss is set, before i go drop $240 on ics or $100 on egr valve ### i have to pass emissions i cant do the egr block mod. Has any body had this same problem any info would help alot

DSM 4 LIFE

 

[dented_coffee]

Hate to tell you this but it sounds exactally like what my talon was doing when I got it. It would pulse a bit when I stopped but only for a second or 2 them leveled out to normal RPM's.

After some testing I found out that my ISC had a bad coil from someone adjusting the BISS screw on the TB the wrong way without following the proper steps.

Test your ICS to make sure it's still within spec.

HERES HOW TO TEST YOUR ICS:

Use an OHMS meter to test the pins on the ICS. They should all be reading between 28-33ohms. If the ohms readings are out of that range then it's going bad and if you get no readings at all then that pack is dead.

TOP OF PLUG
1 2 3
4 5 6

Test the pins in this sequence to get each ohms reading.
1-2
2-3
4-5
5-6

 

[And_44]

Vacuum leak can be an annoying issue too. And you still have the emission equipment. Those add ALOT of feet of potential vacuum leaks. Cheap easy fix, 8-10 dollars for hose and 90min to 2 hours of your time cutting and replacing.

 

[bigpoppa694lyfe]

it wouldnt hurt to replace the vaccum hoses even if they are fine. Odds are that your car has the factory lines and being that they are a common problem on forced induction cars where the heat is considerably higher... $10 and a couple hours now can save u alot of headach's later

 

[izzone913]

My 90 tsi awd had same thing and it was my ecu. I have an extra TPS and IAC both for 90's if you want pm me.

 

[gtbread77]

Hate to tell you this but it sounds exactally like what my talon was doing when I got it. It would pulse a bit when I stopped but only for a second or 2 them leveled out to normal RPM's.

After some testing I found out that my ISC had a bad coil from someone adjusting the BISS screw on the TB the wrong way without following the proper steps.

Test your ICS to make sure it's still within spec.

HERES HOW TO TEST YOUR ICS:

Use an OHMS meter to test the pins on the ICS. They should all be reading between 28-33ohms. If the ohms readings are out of that range then it's going bad and if you get no readings at all then that pack is dead.

TOP OF PLUG
1 2 3
4 5 6

Test the pins in this sequence to get each ohms reading.
1-2
2-3
4-5
5-6

yeah i ajusted the BISS with the car running at idle and cold when i got the motor running the first time, without grounding the ignition timing plug and diagnostic plug. so its ###### ics then idk ill keep you guys updated,it was before i found out it was the BISS. thought it was just simple idle adjust screw

I don't hav maft translator or gm maf and im running atmosphere dump bov could that also be it. im thinking bout gettin 2g maf would that help?

Vacuum leak can be an annoying issue too. And you still have the emission equipment. Those add ALOT of feet of potential vacuum leaks. Cheap easy fix, 8-10 dollars for hose and 90min to 2 hours of your time cutting and replacing.

alright ill try this first

 

[gtbread77]

Just a update that is FREAKIN AWESOME!!! I checked the isc and found it was actually ok, Sweet!!! so i found on identifix (borrowing account from buddy) they found that the biss screw was backed out to far causing ecu to hunt for correct idle, causing surge. so if you messed with your biss screw and your having similiar surge problem check this first it saved me bout $240. HAHAHAHAAHA

 

[92AWDHX40]

Yep that would do it, that biss screws it sure is pesky.