so... ive recently got myself a nice 53 plate impreza gx witch when i baught had no problems at all apart from in need of a clutch, so i have just replaced with an excedy. after putting the new clutch n it was sooo much better but 40 miles later, it started getting a very weird idle problem witch i cant quite put my finger on the cause..
it all started while stopping at a roundabout and as soon as i clutched in the revs just went straight down and it stalled, first of all i thaught it was the lack of fuel it had in, but there was no jerking around which is usually a sign of being low. so i tried starting it with a little bit of throttle and it fired up but wouldnt keep idle, anything below 1500 revs and it would sound like it was misfiring and stall. so got it home and looked on here for any info and found that it could be the aicv or throttle plate, so cleaned and reinstalled those, but no luck, went and got a replacement aicv and still no luck, so i then replaced the spark plugs and checked the ht leads and all thats good. and now my head is about to explode as i cant find the problem! i am a honda engineer and new to the imprezas wich ive loved for as long as i can remember.

my car is not starting unless i press the accelorator then once started it wil rev fine past 1500revs but then it will blip up on the over run back down and any thing under that it sound like its misfiring but its not and it will tick over at about 300revs and slowly die.. and a new thing wich it has just started doing is revving itself up to about 2500 from just a feather of thottle. its completely standard apart from a set of 17" weels and a cat-back exhaust system fabricated by myself.
has anyone on here had similar problems with theirs before i lose the will to live lol. any info greatly appreciated..

 

Any codes? u dont say what car , but , ifs its a classic use the black plugs

 

sos my mistake on saying u didnt say what car. u should be able to get the codes read nontheless. have u checked all vac pipes ,

 

just a thought , but on classics, and i assume it hasnt changed, theres a return spring for the clutch fork top of the gearbox. check this hasnt been put on somewhere it shouldnf have , and displaced something.

 

Hi yes ive checked all vacuum lines and none of them seem to be a bother,i have one code, which is a p0558 which has something to do with my alternator but it ran fine when this shown up, il check it again today to see if any more has shown up l, hope it has so it can tell me the problem, im also going to check the voltage the tps is giving out to see if that got nudged in the process of doing the clutch.

 

Just looked for a spring near the clutch fork and there isnt one so cant be anything round that.

 

Is there an idle control valve on a N/A version?

Matty has some for sale at £10 if they are the same as the turbo versions.

 

Yes they do, i went to a local nreakers and got one off an imort legacy and it made no difference at all, ive cleaned the throttle plate and aicv with carb cleaner and it looks like new, so there out the equasion unless the aicv i got was knackered, could it be a lambda sensor down wich could cause this issue?

 

Maybe maf?.

 

check crank and cam sensors and associated wiring. might be worthwhile checking the knock sensor as its in that area.

 

Plugged it into diagnostics and no more codes than what was there before.........
So pent the last 5 hours in my workshop today trying to find the problem, I wiggled and made sure every connector I touched when doing the clutch was firmly connected, i also checked the cam sensor, crank sensor, knock sensor both lambda sensors and any others I came across, I also took the throttle plate off yet again and cleaned all the sensors on that including recalibrating the tps. And then I replaced all gaskets and o rings I came across while doing it to make sure none of those are seeping, all this while the battery was disconnected so the ecu could reset its self. Connected everything back up made sure everything was in place, turned the ignition on left it for about a minuite.... she fired up fist crank and purred like it should!! So I dont know where in the process I fixed it but I have managed to.. thanks for the replies people, they helped.