Can some one point me in the right direction?

My 93 wrx has started to run very poor when cold. It almost stalls when I fire it up, my air/fuel ratio meter goes off the scale showing overfuelling and if you don't give it plenty of throttle when you lift the clutch up it almost stalls again. After about five minutes it runs fine and I won't have a problem again until the next time the engines been left for a while.

I had new spark plugs fitted last year and TSL said the coil packs were fine (I asked them to check just in case)

My MOT last month was fine for the emissions test so I wouldn't think it was the lambda

I just don't know where to start looking

Anyone had a similar problem?

 

So many people and not one with any help - come on guys, where's all the experienced members?

 

Temp sensor would be a could call to start with i'd guess

 

What air filter have you got and when was it last changed/cleaned? Could also be the notourious MAF.

 

I've got a supposedly good maf in my shed somewhere, I suppose I could give that a go. Just wondered why a faulty maf would cause overfuelling when cold but fine when the engine is warm???

 

Couldn't tell ya why but if you have a spare one it won't hurt giving it a try. Reset your ECU aswell just to start things from scratch.
What about your air filter? If its dirty/oily/damp it won't be letting through enough air to mix with your fuel which will cause over fueling and if your MAF is knackered it won't detect this to re-adjust you air/fuel ratio.

 

are you sure its not the lambda sensor, afaik the car runs alot different once has warmed up, hence passing mot? just a thought.
also giove the temp sensor a try and as stated before try the MAF change you have.

tim

 

If the radiator fans start running as soon as you turn on the ignition, it will be the coolant temp sensor - located on the top of the engine, under the intake manifold.

About £30 for a new sensor.

 

I would say coolant temp sensor too although it would still be rich when warm..

lambda is not used until car warm so unlikely to be that.

check plugs too..

Simon

 

Air filter is an ITG one so I'll check that.

Fan doesn't kick straight in so maybe not the coolant sensor??

I'll try the maf as I have a spare - spark plugs have only done about 4K so should be ok

I'll also do the check engine thing to see if it's reporting any errors

 

The MAF sensors on the old cars <99 aren't as prone to failure as the 99> cars. It sounds like a temperature sensor fault to me.

 

Get back to work you

The temp gauge on the dash works as normal so wouldn't a faulty sensor affect this too or is that gauge fed from a different sensor?

 

no different sensors..

 

Do you know which plugs they fitted? It sounds like they could be a possible cause.

 

KN 07's I think although I did have this problem about 2 years ago before the plugs were fitted. I never did find out what the problem was though, it cleared on it's own before I got to the root of the problem.

Thinking on, it occured before my fuel pump failed??? Could a failing fuel pump cause this fault though? Surely it would do it all the time and not just cold?

 

How long ago were the coils checked?

 

About a year ago.

Jolly Green Monster - thanks for that, I'll bear that in mind

 

Well I did some checks at the weekend and I think it could of been the MAF. I did the check engine thing and that was clear, no faults showing, so I changed the MAF with the one I had lying around and touch wood it hasn't done it since although I've only used the car twice from cold this weekend. I suppose I'll just have to wait and see

 

Damn! took the car out last night and it started doing the same fault again. Air/fuel meter going straight to rich, engine running very lumpy and almost stalling until it was warm then ran fine

Is it worth changing the temp sensor even though the diagnostic check engine thing didn't show any faults?

 

Anyone got any more ideas?

 

Hi just wondering how you tested the air fuel meter. I have just changed my MAF and its still drinking fuel. I am getting about 30 miles from a tenner. But think its down to the coil pack because I have had to reduce the sparks to 6 mm to get it to run ok. Will you let me know how you get on.

 

I just swapped the maf for a supposed good one, I didn't actaully do any "tests" on it

 

please let me know how you got on and what the problem was I have exactly the same problem with my car and I dont know where to start looking!
Thanks

 

No neither do I, that's the problem

 

Charlie, did you change the temp sensor?

These tend to die over a period of time. I can't remember if the CEL illuminates, but it could explain the symptoms you are seeing. Worth £30 if you are stumped for any other ideas?

 

Suppose it may be worth it although I've checked for any sensor faults with the CEL/black connectors and it is showing clear? I'll see if I can get one this Sat from my local dealer

 

charlie,
did u get this problem sorted, as i'm now in the same boat. have replaced plugs and lambda. did u try the coolant sensor as suggested?

does anyone have any ideas.

cheers

 

Not yet, I've just got hold of some good coil packs to try but I've been busy installing a new bathroom suite so I've not got round to it yet. Might get chance this weekend, I'll let you know

 

Damp/dirty HT leads?

Doesn't really explain the rich AFRs, but when I had cold start and misfire problems I resolved it by removing the leads one at a time and giving them a good clean with some WD40. Mines just started to get a bit lumpy on startup again in this cold weather so I'm going to try cleaning them again. Clears after a couple of minutes though.

 

i've tried temp sensor and still no joy, how did u get on with coil packs?