Clarkie GT

My 95 WRX isn't running right...

it runs fine till about 2.8k rpm then starts misfiring really bad, and Air/Fuel gauge reads very lean... if i rev through it to around 5k it runs fine.

im suspecting faulty MAF, has any one had this fault before?

magneel1

iTrader: (18)

Does your car randomly cut off when yr foot is off the throttle?

This used to happen to me when the MAF was on its way out..

There's a said test where you leave yr engine to idle and unplug the MAF where the engine should then stall. If it does not stall the MAF has apparanly failed. (Im not 100% sure about this)

Splitpin

Let's deal with that one first then. The procedure you've described above cannot determine the difference between a functional sensor and a damaged/degraded one. It's total, dangerous, bullsh*t, no other description for it. Proves absolutely nothing - and can easily give false confidence in a badly degraded sensor.

Clarkie, mass airflow sensor is a very likely explanation but by no means the only one. Has this started happening all of a sudden or has it gradually got worse and more noticeable? Is it also equally bad in every gear, and is it equally bad if you let the revs climb through the "bad" zone on light throttle as if you try and accelerate hard through it?

Do you know anyone local with the same model car you could borrow another MAF unit from to try?

magneel1

iTrader: (18)

Yh I was not too sure, Ive read it here on the forums.

Splitpin

Yep. No doubt the people repeating it mean well. Unfortunately, it's the type of well intentioned misinformation that can (and has) resulted in people blowing their engines up.

I recall one here a few months back where he'd tried that test you were on about, and his sensor "passed", when in reality the sensor was totally b*gg*red - and killed the engine a short time later.

Salutory tale that.

Clarkie GT

Splitpin... it's started since it'd been sat for 6 months, and no, its not load/gear relitive, happens at all thottle positions and all gears... just always 2.8k.

and yes if i light throttle through 2.8k to around 4.5 to 5 k its then fine and runs perfect.

Splitpin

Hmmmm, slightly contradictory symptoms that, at least if I read your post correct. If it always mucks about at 2800rpm even on light throttle then it could be that you have a couple of separate problems interacting. If you can get through the "bad" area on light throttle then this points the finger a little more firmly at the airflow meter.

Do you have access to any datalogging kit or a reasonably good quality digital multimeter by any chance? If so, going for a drive with the DVM hooked to the MAF signal and sensor ground cables running into the ECU (or looking at the voltage input via a logger) should throw some light on whether it's the airflow meter or something else.

Other than that, as above either borrow a known good sensor or take the car to your nearest specialist for a diagnosis. The one thing you don't want to do is carry on driving it until you've pinned the cause of the problem down (or at least ruled out the most destructive potential causes).