Hey, I have a problem with my 1990 subaru Legacy. The engine is really rough below about 3000 RPM's and just shakes Violently. This problem only occurs some of the time though. And when ever I take it to a mechanic where they they can look at the computer, the problem just disapears and they say that the computer purges all the data so that does no good. They said it might be the fuel injectors and other such stuff. Whats up with my car? I've tried BG44k fuel injector cleaner, replacing the air filter. Recently I've replaced some fluids, the oil and oil filter. Its got a new water pump and timing belt. Suzzy Subaru only has 64K miles on her and I'd like to keep her up but this is just odd. The Check engine light only comes on once in a while, but old Suzzy just can't shake of this off. After the car sits over night The problem ushally subsides for a period of time. Anyway thanks for reading this. Hope you can help.

 

~Nathan

Go to my site, notes & tips, engine related, and pull the ECU codes. If the cel comes on, a code will be stored, and you can read it yourself.

Rough running at low revs is often caused by a vacuum leak. There may be no codes displayed. The leak is often in the hoses which, with an older car, have become cracked or split at their ends.

 

In my 1991 legacy the leak occurred at the junction between the air inlet duct and the inlet manifold. I spent a lot of time looking for it but the agent found it real quick. I guess he put a vacuum gauge on the manifold to check for vacuum leak. You could try squirting oil over the various air inlet joints to see if this improves performance as this acts as a temporary seal. It is an old technique but personally I have not had much success with it.