Diagnosis? Car won't hold idle...
 

The '92 SVX had just had the alternator replaced with a brand new factory Subaru alternator.

I removed the alternator to place it in another SVX for testing purposes, then replaced it back into the original '92 SVX and put a re-built alternator into the other SVX. This is when the problem started.

At the same time, I also cleaned the short ram air intake cone, and re-installed the cone.

I drove the vehicle a few times since then, and it died on me while traveling down the road. I got it to re-start and drove it home. Now, I'm unable to start the vehicle, and have it idle correctly.

I can start the vehicle and keep my foot on the gas - at around 2500 RPM, and it'll run. If I let my foot off the gas, the vehicle will quit running. If I bring the RPM up to ~3000 RPM, the vehicle will start shaking like a monster V-8, vibrations which are not normal.

I've replaced the fuel filter as well, done recently (last three months). I checked the MAF by unplugging the unit to see if it would idle at all, and no luck there. It doesn't make a difference, limp mode isn't enough to keep the vehicle running.

Any clues or suggestions on something that might be a "common" problem area?

Re: Diagnosis? Car won't hold idle...
 

The beginning of your post is a little confusing...... if you mean that the SVX that you reinstalled the cone filter on is having the problem...... then I would suspect that if you re-oiled the filter, oil may have shed from it and fouled the MAF vane. I suspect this because you said it happened shortly after you did this, and your symptoms are indicative of a possible MAF issue. Clean the MAF and see if that helps would be my first guess.

Second guess would be the crank angle sensors directly under the alternator, since you could have possibly accidentally nailed one when you did the alternator swap.

Re: Diagnosis? Car won't hold idle...
 

Thanks for the help! :) I'll check both of those out, and see if I might have damaged the Crank Angle Sensor. I don't believe that my wife re-oiled the filter, though.

Re: Diagnosis? Car won't hold idle...
 

How could she clean it but not re-oil it? Is it paper? This really sounds related to mixture control, and since you were working with the filter, id check the MAF first (spray it out with MAF cleaner or Brakleen). Limp mode cannot compensate for a bad MAF signal because it cannot substitute any value for a dynamic throttle dependent airflow reading.

Re: Diagnosis? Car won't hold idle...
 

Take that filter OFF and put one without oil in (ie one that says "subaru" and goes in the box that serves the purpose of directing cool air into the engine) You'll have more horsepower and less problems.

Re: Diagnosis? Car won't hold idle...
 

It's a non-oiled (paper) filter. It was still a little damp from washing it out when I reinstalled it, but not dripping wet to the point that water could've been sucked into the engine either. Could a little water mist possibly foul the MAF?

-Roo's wife

Re: Diagnosis? Car won't hold idle...
 

Washing out a paper filter :confused: Well at any rate clean the MAF first since it can be done in less than 5 minutes and it was something touched before all this happened. Then just for kicks, disconnect the battery for 1/2 an hour to reset your computer.

If this doesnt help, then carefully inspect those two sensors under the alternator.

Re: Diagnosis? Car won't hold idle...
 

Update... the issue has evidently been resolved. Hubby installed a new fuel pump and she's running just fine now. :)

Re: Diagnosis? Car won't hold idle...
 

Update was typed too soon. Car ran first time it started up - after the battery has been disconnected. Second time we tried to start it, it won't hold idle again...

...same problem.

Re: Diagnosis? Car won't hold idle...
 

No check engine light?

From your first description it seems to be a random misfire....

Since this all happened after the alternator swap and filter clean (paper :confused:) I would look first at those two areas. The symptoms you described seem very close to a bad MAF sensor....... but could also be a crank angle sensor since you replaced the alternator. You might also check the voltage that the alternator is putting out, since its a rebuilt right?

There are testing procedures for all of these, in the online service manual, the link to which you can find below in my signature. All you need is a multimeter.