I'm having an odd issue with my 04 STI. If the car is sitting stationary, clutch pedal in and I just barely tap the gas, the idle will dip very low - like down to 200, 300 range (sometimes it will die) and then slowly come back up. Similarly, if I'm coming to a stop and push the clutch in it will do the same thing. Sometimes this problem nearly goes away (doesn't drop rpm's as much) and then comes back seemingly at random. Currently the idle is set to 1500 rpm's - we raised it during 100 Acre Wood when this problem started in hopes it would drop to only like 1000 or 800 instead of 200 but it didn't really help. So it was doing this same thing on a normal idle setting and an elevated setting. relevant info: 3" turbo back, tgv deletes, gms turbo inlet, perrin intake, walbro 255, gmbcs, 11lb flywheel (idle was fine when this was originally installed), 11:1 cr, 100 octane, open source tune, stock vf39 with a 34mm restrictor, stock tmic. We just re-tuned the car and everything else seems normal. Our baseline pull was pretty much identical to the last time we dyno'd. Settled in on 220whp/287wtq at RS Motors at 16psi. the only other issue the car is having right now is the engine temp is taking a long time to get up to operating levels (threw a P0128). Has a mishimoto radiator and a gms 170 tstat - not sure if this would be related to the idle problem or not. Not really sure where to go with this now - possibly an issue with the drive-by-wire throttle body?
could it be the MAF even if it's not throwing a code? I cleaned the maf and put on a new filter after 100 Acre Wood, also put in a new front O2 and MAP sensor at the same time (different issue - possibly related? car was over fueling which DNF'd us day 2).
Do you have a water temp gauge and sensor or relying on the cluster's temp gauge? Not sure if it relates to the DBW
I just notice off the stock cluster, Ron noticed it wasn't getting over 170 when he was tuning yesterday. Had to turn the fans off for a while to let it come up before we could tune. (basically what I notice if I drive it on the street. Cruising speed the gauge reads very low - right at the bottom. If it sits at idle for a bit the temp comes up to the middle, same if I drive it with the revs up for a while). I need to pressure test the system again - I thought we had found and fixed any post maf leaks but maybe there's a new one or an intermittent one.
no it's something i need to get installed. some co-driver had lined one up but then never went and got it... I have a gauge I use with my pressure tester I may just hook up temporary to see
i know my answer is of no help since my car does it to (granted mine is not an 04). Has it died on you yet when you push in the clutch? Since thats what mine will do, only once per drive if even that much. even though with a vented bov it doesn't help matters either with the drop in idle (on my car anyways) I have gotten the problem to be a little more steady (as in not dropping as much) by playing with the IAC output line, i put hose clamps on instead of the stock metal spring clips or whatever they are. so i don't know if pointing you towards the IAC may help, but its worth a shot.
see what i mean by no help, sorry i don't know the new sti/wrx's very well. and i just googled it for my sake, and you are correct the DBW does not have an IAC. the throttle body is your "IAC"
My STi did something kinda like that, idle low would die at stops. Do you have adjustable fuel pressure regulator? I adjusted my pressure up about 5 psi and it hasn't done it since. I got a boost gauge you can have
I want in on answers to this too. My 04 sti will randomly do this too. Mine is all stock except for intake and a catback. Just like carl described when you step on the clutch sometimes i will literally see my idle drop to where the car is almost going to die and sometimes it actually does die making me look like a total newb.
My mishimoto takes a very long time to get up to temp too, was annoying in the winter waiting for heat lol.
yea like nate pointed out the MAP was just replaced. It had this problem on the old MAP and now the new MAP. What tstat is in yours? I just took the gimmick 170 out, going to put in an oem one again to see if that helps.
I been telling carl for a while now and we finally confirmed my thoughts....the gimmick Tstat was jarred/failed open and never allowed the engine to get up to temp. replaced with oem replacement and everything is back to normal. we also re-circed a hose that was coming off the custom air/oil seperator and fixed a after maf leak. after all that the car still dips a bit, but not like before....it seemed to dip maybe 300rpm or so...but now stays above 1000 rpm (due to higher idle settings) versus before when it would threaten to stall or dip very low. I'm pretty pleased with the progress...I think carl is too.
it's back. maybe a new post maf leak. I'm going to put the pcv system back to how we had it for n/a mode and try to get the turbo inlet to seal better (seems to be leaking from there now)
martin and I put the pcv system back to how it was last year when we had no idle issues and re-sealed the turbo inlet. It's still dipping idle but not as bad (dropping to only like 1,000 or 800 instead of sub 500).
