Rough Idling!

[butler]

On my 97 sti when driving then come to a stop the revs start to drop till the car almost stalls then climb again to about 1100 rpm then down again, does this for about 20-30 seconds then returns to normall. Anyone have any ideas to problem? Cheers

[speech]

Do you have an induction kit fitted?? On other cars in the past I have experienced lumpy idling when I came to a stop due to heatsoak from the engine.

[butler]

No induction kit m8, forgot to say engine is totally standard.

[euan_r]

have you got standard dump valve? if not check that first.

probably that old favourite maf sensor.

i would clean idle valve as well, couldnt tell you how though as i have yet to do this on mine.

[butler]

Still has the standard d/v. Took the idle control valve off and cleaned it couple of days ago but still the same. Unplugged the maf when car was running and it cut out which suggests that's fine (i think). The car tends to idle rough sometimes not every time i come to a stop. It's doing my head in .

[jodie typeRA]

i will go for the ICV ..my car was doing the same, over time it got worse and ended throwing the check engine light up . i tryed cleaning it aswell (you did take the hole icv unit off yeh and not just the cap) and it did not word..

get hunting iff its is mate thay dont come cheep. about £260 from subaru.

have you had a look to see iff these any faults held on the ecu?

[euan_r]

i wondered if it could be pcv valve. my theory is dodgy though so maybe someone who knows more could either confirm or tell me to shut up. i was thinking it was happening when comming to a complete stop with clutch down as the brake booster vacum comes of pcv valve i think, does on a n/a anyway. wouldnt harm to clean it i suppose.

[butler]

I took the connector that sits on top of the manifold off and gave that a clean. Is that the right way?

[seafar99]

I took the connector that sits on top of the manifold off and gave that a clean. Is that the right way?

Yes, but check the condition of the rubber'O' ring , could well be the 'O' Ring needs replaced on the idle control valve.

[butler]

Were is the oring located?

[seafar99]

There are two screws on the right hand side which let you open the icv there is an 'o'ring seal which would be worth checking, this will take all of 5 minutes.

[butler]

Ok mate cheers. Will give it a go tomorrow see how it goes.

[butler]

Took the ICV off yesterday and gave it a good clean, Rubber o ring looked fine too. Been out in it today and seems to be ok, When i started it up though coming back home the revs started to drop slightly and up again but fine when coming to a stop. Could the lambda sensor cause this kind of problem? Had a punto gt few years back and idling was rough due to lambda.

[thefastone]

have you tried checking the ECU fault codes? think that could be the best way to go mate!

There's a really good write-up on how to do it here: Reading ECU codes (classic Impreza only)

[butler]

Think i'll have to give that a go now. Still doing it and does it on start up now .

[butler]

Just done a ECU error code check, Showing no faults. Anyone think of anything else?

[thefastone]

Well my usefullness has just expired...

[superstar_tradesman]

sounds like a dodgy maf, strange it's not thrown a CEL tho.

[thefastone]

oh now theres a thought... am I right in thinking that you may not get a Fault code if it comes on gradually...? IE: if you reset your ecu and then check the codes again, it may well throw up a code that hadn't been flagged before...?

Dont know, But I seem to remember someone saying that before... or am I thinking about something else...?