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Hi Folks::

I have searched around a bit and can't seem to find anybody with a similar problem--

I've got a '92 wagon EJ 22 with 5 speed manual transmission, 213k miles.

I was cruising down the street yesterday, ~30 mph in 3rd gear, and I lift off of the gas pedal, but the car just keeps accelerating. I shift into neutral, and the RPMs keep rising rapidly like the throttle is wide open so I kill the ignition and roll to stop. First thing I think is the throttle cable or throttle body must be stuck open-- but neither is the case-- all looks normal. I try starting it up a couple of times, same thing-- engine acts like its going to go all the way up to redline so I kill the ignition. I try disconnecting the IAC, same thing, then I disconnect the MAF sensor and the car will start up but immediately tach up to 2500 RPM and hang there, running very rough and spewing quite a bit of smoke out of the tailpipe, evidently running very rich and smelling like gas. I then reconnect the MAF, and the same thing still happens. I tried swapping to a junkyard picked MAF since the housing on the one in the car was cracked anyway, no change-- car is still starting right up but idle is at 2500 RPM, very rough and shaky. I have a junkyard IAC I could try but I don't want to bother unless there's some chance it might help. Anybody have any clue what's going on here?

No CEL, didn't make any mechanical changes to the car apart from an oil change several weeks ago. Car gets driven maybe 4 times a week, 4,000 miles at most per year.

Thanks for reading.

Welcome to the BBS.

A bad TPS sensor could cause what you described. Try removing the connector for the TPS and see if the problem is still there. If it's not, then I'd suggest checking the TPS per the diagrams below. If you replace the TPS you'll need to calibrate the new one via the instructions in the third scan.

http://www.main.experiencetherave.com/s ... sting1.jpg
http://www.main.experiencetherave.com/s ... sting2.jpg
http://www.main.experiencetherave.com/s ... sting3.jpg

Josh :

Thanks very much for your reply.

Disconnecting the TPS and starting the car makes it first do the high idle, then throttle just keeps opening as it did initially.

Not worth a shot to try the IAC, huh?

Thanks again.

Hmmm

Have you verified that the throttle plate is closing completely? If removing the electrical connector for the IAC valve doesn't do anything, then I'm not sure changing the IAC valve will do anything.

Does your throttle body have this screw on it?

http://www.main.experiencetherave.com/subaru/images/tb/

If it doesn't then another possibility could be an intake/vacuum leak. I would try pinching the IAC valve hose to see if reducing the airflow to the IAC valve causes any difference or not.

I'll take a closer look at the plate tomorrow to see what's going on with it when the car is running, check for that screw & pinch the hose to see if it makes a difference. Just about out of daylight over here and it's raining.


Thanks again for your expertise!

Josh::

Thanks for the reality check-- I pulled the intake ducting off the throttle body, and sure enough, there's something jammed under the throttle plate. I didn't have time to carefully remove it, so I'm going to go back after work and see what happens when I do. Since the car ran so poorly, I'm wondering if some debris already got pulled into the intake manifold. I expect it's pieces of the old cracked MAF housing which I just replaced. Is there a chance some of it made it through the intake manifold into the cylinder head? Hoping not.

edited for clarity!

Well that's good to know....at least you found the cause.

Regarding whether there was any more material sucked into the heads. I would think if that happened, you'd know. What I'd suggest doing is removing the throttle body or at least unbolt it from the intake manifold if you don't want to have to disconnect the coolant lines that run through the lower part of the TB. This will hopefully give you enough room to remove any debris and look into the intake manifold to see if there is any other debris in there.