davefaulder

My 94 uk turbo is having problems idling. When you are driving it and you dip the clutch and the revs drop they are dropping too far, down to about 500rpm sometimes. Normally the car would idle faster at give or take 1000rpm or slightly below.

Anyone any ideas what may cause this?

Thanks

Dave.

Postman Pat

I had the same problem with a MY99. It turned out to be the MAF. 99's are known for this though. BTW the dealer hadn't a clue because as the MAF was not totally buggered it didn't generate any fault codes.

Pat

muly

davefaulder, i have a maf sensor for a 94 wrx ,its on ebay at the moment,but may be able to take it off if you need it

Nick200

How much for it m8??

smigga46

Had maf changed at the weekend only cut out once but had it checked straight away, when ecu was reset hunted all the time had learnt to accomodated the problem, get it checked and replaced £73 cheaper than engine rebuild.

SilverTurboWagon

Why would the MAF playing up require a rebuild? Just curious as I did a reset tonight and the idle is a little bit of a see-saw between 750-1000.

Dark Blue Mark

If the maf fails lean, it will cause underfuel on boost which causes det, which will melt your pistons.

My bet is either the o2 sensor, which can be checked with an AFR gauge. Or more likely the Idle control valve sticking, or the throttle sensor being out of range.

Both can be checked easily.

MB

Dark Blue Mark

Just to add, on the pre MY99 cars, the MAF is a fair bit more pricey as you can't just buy the element.

MB

muly

Nick200- want £40 for the maf

Nick200

Is it new?

If not how long you had it on your car, also why haven't you got it on car now???


I am very interested and will pay 40 quid m8.

muly

Nick200- it was tacken off my mates scooby as he has a link ecu or something as does not use the standard scooby maf, his car had 44,000 miles and ran with standard filter

davefaulder

Muly - Thanks for the offer. Did you sell it in the end? Sorry I was slow getting back to you.

Dark Blue Mark - How do I check the idle control valve and the throttle sensor. I do have mechanical skills but I'm not sure where those are on the car i.e I can strip it down and have a look at it if I can find it. The erratic idle problem seems to come and go. Isn't affected by engine temp doesn't matter if the car is hot or cold.

Thanks for the input guys.

Dave.

Mal26

Dave, I have exactly the same problem - dont think it is the MAF and replaced lamda so want to check th idle and TP sensors. Hope someone replies!

Dark Blue Mark

Copied from one of my old posts:

http://www.scoobynet.co.uk/bbs/showthread.php?t=293030

If your 02 (lambda sensor) is shot, you will probably have crap fuel consumption, as your engine uses this sensor off boost.

If it was MY99 / 00 then your MAF is the most likely culprit. Pre 99 MAF's are pretty good it wouls seem, so I would look elsewhere.

1st check is the throttle position sensor, which is on the throttle body. With the ignition on, but engine off, you need to check the output from the sensor. Disconnect the sensor plug, and stick a multimeter on it. Middle pin is earth, and use the outer one as the signal. Set the multimeter to Ohms.

You should get about 0 when the pedal is at rest, and about 5 when flat on the floor, and it should be linear. 2 man job as someone has to push the pedal

Also spay some WD all over the trottle spring area for good measure.


Next culprit is the Idle valve. Its on the right hand side, just down from the intercooler, and has A B C written on the lid, which is a cream colour. There's a pipe running to it from the airbox. Try and squirt some brake cleaner in there with someone giving the car 3k revs. Or you could use both hands and pull the throttle cable

If you do a search you can find out how to strip it down.

Do an ECU fault check too

MB

Dark Blue Mark

Just to add,

Mark around the screws on the top of the ISCV before removing it. Adjusting the position of it will adjust your idle.

MB

davefaulder

Mark - What constitutes poor fuel consumption? I get about 190 - 200 miles for £35 - £40 worth of super unleaded.

I'll check the throttle position sensor tomorrow in the daylight. Hopefully that will be the problem.

How do I do an ecu fault check?

Thanks help is appreciated.

Dave.

Dark Blue Mark

Dave,

On a Uk car, you should be getting anywhere between 250 (hard driving) and 300 miles from a full tank. Bearing in mind the older ones have a slightly smaller tank.

My STi gets about 200 (bigger injectors), so you should be getting much more than you are. It sounds like your off boost fuelling is bad, hence the thought its may be the o2 sensor.

TPS sensor is easy to find, as its on the throttle body, with a plastic connector going into it. Would suggest also taking the lid off the ISCV and see if the spindle inside is free to turn. I dont think its the ISCV, given your consumption, though. Reset ECU after all of above.

ECU fault check / reset instructions can be found here: http://www.ravensblade-impreza.com/faq/faq1.html about halfway down the page.

Ravensblade is a complete bible

Very easy to do.

MB

davefaulder

Ok I'll try the tps and the iscv tomorrow and see if that sorts the problem. If not then I'll try resetting the ecu.

Incase it makes any drastic difference to the fuel consumption my car has the following:-

Bailey atmospheric dump valve
Full turbo back Trust exhaust
Pipercross cone filter
19" Oz wheels

The car has never done more than 210 miles on a full tank since I got it. Granted I don't drive it that easily and I'm often found pushing it along rapidly down country roads. The car often pops and cracks on over run as you let off the throttle but I was always just told that was because of the exhaust and the mods.

We'll see how I get on.

Thanks
Dave.