View Full Version : sr20det s13 hunting/surging at idle.

10-30-2020, 10:57 PM
Hey guys!

New to the forum and looking for some advice!
I have a friends s13 that?s had a auto to manual conversion it seems. Still has auto ecu but has manual tps (read both it can make a difference and won?t).
He told me it had issues where when the car got to temp or ?hot? it wouldn?t go over 3000 odd rpms (when first hearing this I thought it could be a fault crank sensor when getting hot sends it into limo home mode or something). Also it was slow. It?s a lot to take in not having worked on an s13 before! I checked the ecu light for errors and there was none. When I wound the ecu screw back fully the engine wanted to die after being turned back on. I found on the internet this screw is also a little idle control valve. Alien to me but after turning it the idle stabled a little. It still hunts badly when idling so I started checking for vacuum leaks. Found the housing coming from the turbo to intake pipe had two out of three bolts striped. Fixed that and kept looking for leaks. It looks like the vacuum hoses were changed recently as they are very clean and new looking. I was then sort of satisfied that there were no more leaks. So I tested the tps and it seemed to be fine. I then tried to adjust the idle control valve by turning the ecu screw all the way back, unplugging the tps and turning the car on. It should have reved high for a couple of secs and dropped but didn?t. Stayed at 2000rpms without dropping. I then turned the idle control valve screw with didn?t change a thing. Then thinking the idcv was clogged or the solo kid wasn?t working removed the intake to get to it realizing the intake gasket had a slight leak. I have ordered new gaskets which will arrive in a week. I then removed the idcv and stripped it down. It was a little clogged with carbon but not so bad to prevent any parts from moving or cutting of air flow. The solinoids both retracted when given 12volts. Where I?m sitting now is waiting to put everything cleaned and new gaskets back together. If the idle is fine I will take it a drive to try to get the not being able to rev when hot problem to occur. If the engine is still hunting after everything testing okay, cleaning everything and fixing little leaks here and there I will have to look into The ecu not corresponding correctly with the tps and such or the new turbo vacuum hoses are too narrow for the spec of the car or the turbo purge valve is not functioning properly. It does have one of the two hoses coming out the valve closed off which I?m not sure as to why this has been done.
Does anyone have any experience with this series of events? Or any advice?

Much appreciated!!