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1G Rough idle/stall

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dc320

10+ Year Contributor
89
5
Dec 22, 2011
CARMEL, New_York
Hello all,

I have a pretty rough idle and at times it wants to stall unless i give it some gas, and after releasing gas it drops to almost stalling or actually stalling.

The car starts fine, turns right over. I did find a thread from 2007 with pretty much the exact symptoms except in the thread the OP had done a 6bolt swap and was running 2g intake manny with a 1g t-body, I AM BONE STOCK, as far as I know unless previous owner put something in that I have not noticed but i doubt that. Here is the link to that thread. http://www.dsmtuners.com/threads/wont-idle-when-cold-and-rough-idle-when-warm.274149/

I had some suspicion it may be the ISC from doing research it seems to be my symptoms. I know when i first got the car i was trying to figure this problem out and I was messing with the BISS screw. I no longer have access to the page I was using to adjust the screw, this was 3 years ago. When adjusting the BISS screw back then I noticed no change in idle, which also leads me to the ISC being bad.

In the thread i linked above, they mention coolant temp senor may cause weird idles, I know the temp gauge in the car isnt the most reliable, but it shows my temps as perfect when warmed up. However the engine/engine bay feels very hot after driving. Hot like i cant even check my oil level after driving or ill burn myself on the dipstick. SO would a bad coolant temp sensor read good temps, i figure it will be all the way up or down if its bad.


I am going to keep scouring the forums and google for more info, but I figure i would post here to get up-to-date and live help instead of 8 year old pages :p


Thanks in advanced for any help anyone gives.
 
Look up how to check the iac. Check it. Could be a fuel issue, power issue, both, vac and boost leak check, pretty much like most problems you will end up checking everything. Definitely make sure the biss is adjusted properly and iac checked. Keep googling. My car feels hot as hell sometimes after a short drive sometimes too.
 
Thank you all for the quick answer, will get a boost leak test done this weekend. I am sure there is some, the car sat for AWHILE and i havent changed out any hoses, pipes,tubes,lines, whatever you want to call em LOL. Also the wastegate is ehh, would that cause any problems?
 
ISC steps range from 0 (fully closed) to 120 (fully open).

To change it properly, you have to ground the timing connector and the diagnostic connector (or hit both those checkboxes in ecmlink). Then verify base timing at the crank pulley with a timing gun, then while having the computer/logger running with isc in real time, adjust your biss until you're somewhere in the area of the idle rpm you want to be in, then further adjust in very small increments until ISC steps are fairly steady around 30.

After each half turn, once you get closer, then you'll do 1/4 turns, then 1/8 turns, and allow about a minute between each adjustment for the computer to figure itself out with fuel/timing adjustments to reach the newly set idle.

Then unground the connectors and you should have happy idle.

**Also verify all other sensor values are in spec. If you t-stat isn't opening and your fan is always running at idle, then the ecu compensates for that by dumping too much fuel because the water temp is way higher than it should be. And there are other sensors that could be making things go haywire as well, having some sort of tuning/logging device is pretty paramount.
 
Yes, it could. Keep in mind if you were turning the BISS screw with the car on the ecu would automatically compensate with ICS causing both to be off. However I'm betting the big culprit is your BISS o-ring. I had a huge leak here, two bucks later I hold 15 psi all day. IMO big vacuum/boost leaks are always suspect with idle issues.
 
Thanks guys, FINALLY got the clutch problem taken care of and now its just small maintenance shit like hoses, pipes, lines, tubes, belts etc etc. Looks like ill run to the autoparts store and see if they have boost leak tester and start there.

Chumpaumpalump im going to PM you with a question quick if you dont mind.
 
So i decided to take a video for you guys, the idle is alot more steady now, but it seems a bit high. IIRC 5speed idle should be at 750. correct me if i am wrong.

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