tomdscooby

Hi folks, i have a 2003 uk sti thats done 40 k miles and my car has deleveoped an intermittent irregualar idle recently. sometimes it's fine, but others it sounds like it's going to cut out, especially when pulling up at traffic lights when clutch is dipped. the dash lights like when you stall it, or turn key to start it etc (NOT CEL) have come on once but other than that it doesnt stall.

it hops about a bit from say 1200 down to 600 ( i think bottom marker on revs starts at 500?) and sounds weird from exhaust, only done it recently and ive not done anything to it mod wise for a long time. only decat centre section, standard otherwise. no VTA BOV,no bleed valves etc, no induction kit.

it drives fine though, holds boost etc, but occasionally it pops quite loudly when changing gear at normal pottering about town speeds,which suggests it may be running a bit rich?

its puzzling me to be honest.

all i can think of to start any ideas is there is a small leak in the exhaust before the back box, and i had my cambelt changed in march.


thanks for any help.

hopefully getting it looked at tomorrow as im currently 170 odd miles from where i need to be by tuesday lol

DaveBeck

iTrader: (12)

idle control valve needs a clean mate. spray some carb cleaner in there.

search on here/web for how to do it

dont worry bout the pops from exhaust

99greenwagon

iTrader: (39)

i had exactly the same problem and i replaced allsorts,it ended up being spark plugs,replace them first and clean the idle valve.

tomdscooby

plugs have only been on for 12k or so.
I've been to where i take it this morning, and as it is, i'm goin back to the garage wednesday to have the idle raised by their mapper(it's not been mapped and isn't being mapped) and gonna try to see if its a coil.nothin came up on the diagnostic machine, and the AFR is fine.its a weird one

99greenwagon

iTrader: (39)

if the car idled fine before then noone should be altering idle speed,were the plugs checked and gapped correctly? they should be set to 0.7mm

99greenwagon

iTrader: (39)

could also be a vacuum leak or leak between turbo and i/c,it dosent take much.could be as small as a pin hole!

tomdscooby

i've got no feelers,otherwise i could check the plugs tomorrow before i go back wednesday. it idles at 700 rpm or 650 at times,and it should be 750 im told.the ecu was reset while it was on the diagnostic tool and it didnt cure it either.any way of checkin the gap without feelers?

DaveBeck

iTrader: (12)

did mine with a ruler. you can get it almost bang on by just looking at it next to a ruler(obviously needs to be a 6" rule with mm on it lol)

tomdscooby

noticed that i have a small leak of exhaust gases after my downpipe where it joins my stainless centre decat pipe. this leak is before the rear 02 sensor so could this affect the idle????????

tomdscooby

all sorted now,turns out it was because the lid on the airbox wasnt seated quite right,of all things lol.

you live and learn hey(feel a bit of a plonker though)