Rough Idle?! Help!!

[tobrien109]

Hi guys

I recently bought a 1994 GF8 Wagon and things have been going quite good until the past couple of days.

When I start up Ilet the car warm up for 3 - 4 minutes and head off. This morning was the worst it has been as I drove out of my driveway and sat at the traffic lights just down the road. All of a sudden the revs started droppingat an alaming rate and it nearly stalled so I responded with a blip of the throttle, the revs raised but then they came back down again, almost as if it was going to stall...

Im not too sure what it could be or how to go about fixing it and being a poor student I dont really have any money to take it to a mechanic.

Any advice would be great!!

 

[94 Leone]

Coils or leads?

Have you had a check engine light? 

Have you checked the  CEL codes?(do you know how?)

Edited September 10, 2016 by 94 Leone

[Rosssub]

Give the idle air control valve a good clean out with carby cleaner. If it only ever does it when it's cold, or only when it's warm it could be a faulty coolant temp sensor. If it's always low or erratic then it's more likely a vacuum leak somewhere.

 

Here's some diagnosis info from a recent thread with similar problems:

On ‎18‎/‎08‎/‎2016 at 10:37 PM, Rosssub said:

Sensor's like the coolant temp sensor can effect idle, warm signal when the engine is cold. But more likely a vac leak or a sticky idle control valve, so best to rule them out first. You will see some pic's of the idle control valve in borland667's garage thread linked below. Remove it from the manifold and give it a good clean out with carby cleaner:

http://www.clubsub.org.nz/forum/index.php?/topic/45394-wrx-sti-v3-restoration-project/&page=4

 

To check for vacuum/boost leaks. With the car idling you can spray ether (starting fluid) around any possible leak spots. If any fluid gets sucked in the idle will change instantly.

 

Or block the intake off at the AFM somehow:

 

Then pump 10-15 psi into the intake manifold with an air compressor. Any leaks will hiss and be obvious.

[tobrien109]

2 hours ago, 94 Leone said:

Coils or leads?

Have you had a check engine light? 

Have you checked the  CEL codes?(do you know how?)

Havent had a check engine light, the leads are fine and I wouldnt have a clue about CEL?

1 hour ago, Rosssub said:

Give the idle air control valve a good clean out with carby cleaner. If it only ever does it when it's cold, or only when it's warm it could be a faulty coolant temp sensor. If it's always low or erratic then it's more likely a vacuum leak somewhere.

 

Here's some diagnosis info from a recent thread with similar problems:

I'm gonna clean the intake and throttle body soon!