1992 Legacy 2.2L non-turbo misses when warm

[szymon]

I have a 1991 (NOT a 1992) Subaru Legacy 2.2L non-turbo engine with automatic transmission. The car runs fine when started from dead cold. After restarting the engine once it has already warmed up the there is a moderate to strong miss that shakes the car. Significant loss of power is felt if the engine is missing badly, and the engine misses throughout driving speed range. The car idles at 500 rpm when warm and the rpm does not fluctuate, the car does not stall. The CHECK ENGINE light does not come on (the car would sporadically miss before it became a consistent problem and a CHECK ENGINE light would go on but all I needed to do is turn the engine off and start it again and the car would run fine)

 

The plugs, and plug wires are only 6 months old (coil pack looks new as well but can't tell for sure if it is). Valve adjustment and ignition timing has been done about 4 months ago when the head, exhaust, intake and valve cover gaskets were being replaced. PCV valve seems to be working although the hose is old, stiff and missing a clamp that is supposed to hold it to the PCV valve. I cannot find and EGR valve (I think there might have not been EGR on this model).

 

Could my problems be caused by a malfunction of the fuel injection system? If so why would the engine run fine when started from dead cold? I don't know when was the last time the fuel filter has been changed, could the fuel filter be at cause? Or maybe air filter is a problem?

 

Suggestions as to what a good next step would be are well appreciated.

 

Cheers

 

Szymon

Edited June 27, 2010 by szymon

[markjw]

Sounds like the o2 sensor.Maybe.That's what I'd look at.

[abog]

You might want to check the coolant temp sensor.

[Olnick]

O2 sensor is a possibility, or might be a faulty ECTS (Engine Coolant Temperature Sensor).

 

Definitely start with the air and fuel filters, PCV valve and new hose too.

[Durania]

Agreed. Check out the coolant temp sensor and your front o2 sensor. Too bad you can't pull the check engine codes so you can start narrowing things down.

[union76]

Since you have an OBD-1 Legacy (pre 1995), you can use these instructions to diagnose the check engine light that's stored in memory (connect the black wires). Count the long (10s) and short (1s) flashes to figure out the 2-digit code:

http://www.surrealmirage.com/subaru/engine.html

 

And here's a youtube video of how to do it: