One frustrating Impreza

So I have an automatic '99 Subaru Impreza L with 180,000 miles (California spec but that only makes things more expensive, otherwise much the same) with some really nasty bogging just off idle. Here’s what’s going on: The car will idle fine and once it’s above 2000rpm will run fine and dandy, but when it’s at idle and I hit the throttle it just about dies. The idle will drop a bit and then won’t budge; to get it rolling I have to quickly pulse the throttle. Once it’s been at operating temp for a while it will get better but I’ll still need to pulse it a couple of times to get it going from a stop.

For what I’ve done, I replaced the MAF which fixed nothing, looked for and found no vacuum leaks, then I tested the throttle position sensor which was fine, then I replaced the MAF again since it was reading high all the time and showing about 3g/s with the engine off and ignition on and I figured it may have just been a bad one I picked up. Well that fixed nothing either.

So now I’m on my second MAF showing the same faults and have no idea what’s going on. The dealer’s next step is to replace the ECM And that’s $700 I’d rather not spend on a $2500 car.

Any clues?


Does the car backfire at all when it stalls?

A bad or dirty EGR valve could do weird things like the ones you describe but they do tend to throw a code when something is wrong.
On a Subie they come off pretty easily so you should be able to clean it with some brake cleaner. Sometimes they get gummed up and are stuck closed or open or get lazy in not opening/closing fast enough.
It would be a quick thing to try and eliminate as a cause.

It doesn’t backfire, no, the rpms dip a little bit and it kind of growls–not much louder than normal idle. If it’s a quick item to clean I’ll take a whack at it just to make sure, thanks for the tip.

I forgot to mention, it does throw codes every so often, misfires in all cylinders. I’ll clear them and they’ll come back after a while, generally after a bit of steady cruising on the highway.