Major rough idle problem

[Endless]

hi all, I have been having the problems that when I stop pressing on the gas throttle, my engine idle will drop below 480rpm and engine stalls....this happen quite often (many times per day especially in cooler days), I bring in to my mechanic to check...they replaced my AAC valve and adjust some timing, also uplift the original idle timing. Car runs great for a week. Then the same thing happen again tonight, which is very annoying, I was stuck in traffic, then idle suddenly drop below 480rpm again and car stalls, restart the car and it happen again, I have to constantly pressing on the throttle to keep the engine running. I stop the car for a minute, start the car again and car has no problem....idle mostly stay at around 700 - 800rpm when no throttle is apply. What could the problem here? AAC valve is replaced and problems seems to go away, but still happen? :rant:

P.S. I have the SR20DET engine

 

[Derek]

If there's a boost leak or vaccum pipe bust the car will stall while sitting in traffic etc.. Check your intercooler pipes etc.. Might be only something small.

 

[Marco_v_w]

I Kick this thread if its okey!

I have the same problems with my car. Everytime when i stop pressing the throttle the engine stalls
I allready changed the AAC valve from my second s15 bud it diddnt help.

Steve told it should be the AFM that is to close to the turbo, but i have this problem allready 2 years

Could anyone help? thnx

 

[andeep]

Sounds like a boost leak. Do a proper boost leak test

 

[TriniGT]

Is your BOV vented or recirculated? If vented either retune or get it recirculated between the MAF and the Turbo.

 

[Marco_v_w]

I have no BOV on the car!

I will do a boost leak test, what is the best way to do that?

 

[TriniGT]

With the car switched off remove the air filter and MAF setup and make a plastic/metal/aluminum replacement pipe with the end blocked off and a valve stem attached to it. Attach that setup to replace the air filter MAF setup and then using an compressor or foot pump or whatever presurize the system to whatever psi you intend to be running and listen for the hissing and tighten or replace vacuum lines where appropriate. I usually go a little above the intended psi to ensure that I will have no problems. You will be surprised to see how many leaks you have and once corrected how much more responsive the car will be.

 

[GUEST_JDM]

Just an idea have you checked the blow by valve on the rocket cover? look for the black hose that comes over the break booster and connects to the left hand side of the rocker cover. there is a one way valve attached to the rocker cover if this leaks or the valve is faulty ( this happened to me) it will cause the idle to become unstable as it acts as a vacum leak. the trick is the one way valve will almost always close under boost but under no vacume it can leak.
Just an idea...

 

[m4rk181983]

i had this problem. it was the intercooler pipe. had a hole in it