Throttle Sticking under boost
 

Hey team just wondering if any 1 could shed some light on a little issue i've been having.

As the title state my Sti seems to be temporarily holding the revs under boost conditions. 3000rpm upwards. It will only hold it there for maybe a second before dropping back down to normal.

Another sympton of the car is that it will idle to 1000rpm then drop to almost a stall and will do this for maybe 30 secs to 1 minute) This rarely occurs though and strangely seemed to correspond with the radiator fan was running. I replaced the battery a few days back because it had ran flat a few times and since have not had that issue re-occur so i'm not sure if they are related, or infact if this has been resolved.

The issue seems to occur more often when the car has been running for a while and i would also say it has been getting slightly more noticeable and frequent over time.

I have taken it into RaceTorque and we had a little look over it, checking the gasket from the top mount to manifold for leaks, which was fine, along with some airlines (where we found some loose ones which we changed). Ironically the issue didnt occur on the way home from the shop but i did occur again the next day. The guys there seemed to think it was likely to be an air leak of some sorts though i haven't noticed any loss of power/boost even when it is occuring.

I have 3 current theories/solutions.

1) The aftermarket BOV (not my doing) sleeve may not been opening and closing smoothly. this would explain why it is getting worse overtime and correlates with the fact that it only occurs under boost. It is adjustable and it currently set pretty tight so it doesnt go off and make a massive racket all the time. I may try and take it apart and give it a nice clean and adjust the spring tension.

2) The second although not my field of expertise is that the car may be in need of a retune. although nothing has changed on the car it has been some 45 000km's since last tuned (exhaust, fuel pump, ecutek tune at mms). I dont really think this is the case though.

3) I've heard that sometimes certain sensors can become a little dirty and need to be cleaned every so often. I haven't had any dash lights come on so i dont think its an O2 sensor or anything, possibly the air/fuel?

Car is a 2005 Sti 2.0L done 147000 and was serviced at 145000 and had a major service at 135000 shortly after i purchased the car. have probably only had the issue occuring over the last 7000km's.

Whilst myself and the guys at racetorque didnt think it was anything catastrophic, it is a little annoying and can be a little dangerous when i back off the gas to brake and the revs along with the car want to keep pushing. so any thoughts or opinions of things i could try or look at would be greatly appreciated.

Your throttle position switch (on the throttle body) needs to be adjusted......It isn't providing the ecu a low enough signal for the fuel cut off to activate when you lift off the throttle.

Google how to do it or see a workshop - you need a multimeter.

Cheers Rossco, i've got a multimeter at home, so will have a tinker this arvo if not, its back to z shop.

In case you haven't done this already, i found a guide and posted it here a while ago;

[url]http://www.perth-wrx.com/vb/mechanicals/53246-adjusting-throttle-position-sensor.html[/url]

Cheers Alternate, that a very good write up. Interestingly i kept following the links and there were a few people that seemed to have idling problems that were sorted out after cleaning adjusting and replacing the TPS, but 1 person still had the car hunting between gears.

A few people claimed that this could be caused by a shift solenoid.

Given that my idling issues seem to have subsided, i'm inclined to think this may be my issue as a pose to the TPS sensor requiring adjusting. Had no time yesterday, nor will I tonight. Looks like a weekend job i'd say.

Can any 1 indicate which plug is the tps switch and where the little screws are to adjust the voltage is on this pic.

Spent 15mins or so cleaning them all, and although i had a multimeter handy testing the voltages was rather redundant when i didnt know how to adjust it.

Cheers

Another pic

[IMG]http://www.perth-wrx.com/vb/members/rossco-albums-hk-450+heli+stuff!-picture4844-tps.jpg[/IMG]

Sweet cheers rossco,

From what i read on the link posted is that there should be some little screws that you can adjust the voltage, i'll have a close look tonight but theres really not much room to tinker with there. Do i need to remove that silver unit to get to them (believe thats the idle air control valve ey)

[IMG]http://ecx.images-amazon.com/images/I/81UjHj6RMKL._SL1500_.jpg[/IMG]

The two (here ^^) screws are phillips head - they are adjusting and mounting screws - the TPS has slotted screw holes to allow for adjustment.