[forgedSTi]

check the o2 sensor

[chumpsteak]

Originally Posted by forgedSTi

check the o2 sensor

I assume you mean the front 02 sensor....how do I go about "checking" it?

[chumpsteak]

Did a pressure check today and found that the turbo inlet had a slight leak. Tightened up the clamp and the leak went away but my idle problem persists.

At this point I'm so tired of messing with it I put the intake back on and reflashed the PDX stage 2 map. Car runs great....super smooth acceleration, holds boost solid in 5th and 6th gear, and idles great at 850 rpm. But then I sit at a stop sign or light for a few seconds while it settles to 700 rmp and starts to shake and make the miss sound.

Should I take it to the dealer? Do they have diagnostic tools that would actually help or are they just going to do the same crap I've already done?

[effect]

your dealer should have a ignition scope to check the problem out..
if your car where to be having a major sensor issue it would put out a CEL.
you can start by checking your air cleaner its a common thing for the car to miss at idle because of a dirty air filter .

or over Oiled air filter is also common.. if your COOL with a smog guy you can have him hook up a Sniffer to it and see what the HC's and O2"s CO2's and EFF of the vehicle is it will tell you alot about the vehicle.. it's only missing at idle possiblities can be alot of things.. one your EGR could be bad.. Leaking injector air cleaner clogged/dirty. an Ignition problem would presist at any RPM range..this only accures during idle. those items i suggested are affected during idle. another thing that could cause that is Timing. i hope you fix your car bad idle issues are always a pain in the ass. if you are able to get a Reading from a smog guy.. i can tell you what the numbers mean..

remember be cool with him just to get a Reading dont want the guy to send to the DMV ( dont know if thats possible) .. if you get hold of a smog guy to do you the favor or maybe tip him.. test has to be at idle and 1500RPM then 2500 RPM..and a vacuum leak! would also show as a miss at idle but not at higher rpm sorry for the random **** it's just that ideas are poppin in my head as i'm typing... anyways Good luck man.

[DjChieNa]

You may have a grounding issue. Either that or you have a dirty MAF sensor seeing that you have an oil covered air filter.

[SiCkSTi04]

how you tried cleaning the throttle body while you had the IC off, could be a build up there.

[Garo666]

My car has a similar problem... At stop lights sometimes (at least 2 times a week) the rpm will rise to 2k and sometimes all the way up to 3k and just sit there ... and when i shift it stays up there or just drops extremely slow...

The shop said they would take a look at it but were never able to replicate it soo ... im stuck with it

[ilikepie]

I think my car does the same thing. Sounds like the idle drops really low, engine kinda stutters. I think its the car just running rich at idle. I got protuned by dough with a catless downpipe and stock exhaust. A month later I got a catless cobb turboback and my car does it here and there ever since. I smell fuel when im outside the car so my guess is its running a little rich.
And about gapping your plugs. You arent suppose to gap irridum plugs. They come pre-gapped.

[awd4life]

my car (04 STi) has done that since day one. i'm also running a OTS stg2 AP tune and honestly i just live w/ it. the engine doesn't die and it only seems the most predominant in hot weather.

i was just recently getting some P0301 missfire codes and pulled my plugs to find them way out of wack. like .050 gap, but i had just recently changed them. after i pushed them back into spec my idle got much better.

if you can get ahold of some software to increase the idle bit by bit i'm sure you would find a speed at which the stumble dissapears and you can be happy again. or try and have someone tune out the stutter w/ fueling and stuff?

[chumpsteak]

Originally Posted by ilikepie

You arent suppose to gap irridum plugs. They come pre-gapped.

Are you sure they come pre-gapped? they were at about .038 straight out of the box and everything I read said they needed to be between .028-.030.

I thought it was the platinums that were pre-gapped.


Thanks for all the input guys, I cleaned the MAF several times and did the grounding mod with no change. I'll clean the throttle body next time I have the IC off, but I noticed it was pretty clean, not much oil or gunk built up at all.

Last night I was driving it and the idle settled in at about 850 and was perfect. No stuttering or missing at all. Then today it dropped back to 700 and started the miss sound again. It's very strange, I may have to look into increasing the idle.

Thanks again for all the suggestions.

[ilikepie]

Yeah you aren't suppose to gap iridium plugs. They are very fragile and you can damage them or break them tips. And after any plug as been in an engine for a period of time, you aren't suppose to re-gap them.

[Tortfeasor STi]

My guesses. Dirty MAF, malfunctioning O2 sensor, cracked vacuum hose creating vacuum leak, clogged iac valve (iac=idle air control). Idle issues can be very difficult to diagnose, as you know. Try reflashing to the stock map and see how it idles then, if it helps you probably need a protune or tactrix cable to lean out the mixture at idle. But I am betting it is one of the above issues and not a mapping problem.

[96golfin]

Any updates to this problem? If you fixed it, what steps did you take?

[SCSTI]

Yea similar to my problem... I actually had a check engine light thrown. It is a running lean code in #1 I believe. I took my 05 sti to a tuner and he upped the idle by laptop to 900rpm. Well that fixed my prior issue which was almost stalling at 500rpm and then shooting up to 1000rpm and then settling about 750rpm problem, but the check engine light came back on a day later ?? Now the car runs ok with a slight stutter every 4 or 5 seconds. I also have a whining noise near the front of the car which starts about 40mph and gets louder when I step on the gas even lightly. It even occurs when the car is slipped into neutral while rolling. I had the clutch replaced 4000 miles ago could that be the problem? Need some help with this one. Tuner says previous problem of code thrown might be the O2 sensor and the dealer said if he replaces it it is not under warranty because I added a FMIC, exhaust and intake. Tuner said Im still running stock tuning so would the three above modifications ruin an o2 sensor???

[juniorsti]

i have taken the same steps you, and most that were mentioned by others and i still have the EXACT same problem.... very wierd.... i got the car protuned by PDX last weekend, and he cant find any problems... just a rough idle. sometimes its good, most of the time its rough....