OriginalSterm

pretty much on a daily basis my idle creeps up. i noticed the screw on the throttle body backs itself out causing the idle to creep up. in fact, it backs itself all the way out to the point where air leaks through the screw (in on vacuum, out on boost i believe). i've followed the instructions on clark's garage by jumpering the two pins on the diagnostic port and set the idle back to ~900 (best i could get). but that screw keeps backing itself out. also with the screw tightened all the way down i blip the throttle and it goes up, but comes back down to ~400 rpm and recovers. it did this before and after the maf kit installation.

on cold starts the idle seems lumpy at first and i simply attributed it to the maf sensor not getting enough air with the lower velocities and pressure pulsations from the engine. but it could also be the air temp sensor making compensations that throw off my air/fuel ratio.

i don't think it's a vacuum leak because i've got a slightly richer condition all across the board that i can't dial out (dyno time and wbo2 may help).

am i looking at an isv problem, vacuum leak, intake leak, tps problem, fuel pressure problem, sol problem, etc.

any insight or suggestions are welcome. thanks!

MHT

try replacing the o-ring on the by-pass screw then setting the speed. The lumpy cold idle could be a result of not enough air from the by-pass. The screw should not come out by itself, they usually take a bit of effort to turn. If you set your base idle speed to about 800 rpm and set the idle mixture to about .8-1.0% measured before the cat w. the O2 sensor disconnected, the car should idle better, esp. when cold. When it is warm the O2 sensor is able to correct for mixture problems to some extent, but when it is cold you are running on basic settings, if they are way off, it will not run well.
Good luck

OriginalSterm

where can i get that o-ring, or what size is it so i can source one cheap (ie free)? that o-ring will help my idle control? the screw does turn quite easily, i mean without a screw driver easily. i hope that's all i need to do to fix my idle, would love a cheap fix for something.

MHT

I can't find a part no. for the o-ring by itself, my microphishe only shows the screw with the seal. I pulled the screw out of my car and removed the O-ring, if you can find one that is 5mm by 2mm it will work fine. Any decent shop that works on imports should have an o-ring assortment and should be able to sell or give you one. Almost any auto parts store should also be able to sell you one.