Hi, I am new to subarus and forums.  but thought I would give it a shot.  I bought a 96 legacy LS a month ago.  one morning I had to turn on defrost and after a few minutes the check engine light came on and the car started running a little rough.  when I turned the defrost off car cleared up.  check engine light went off a day or 2 later.  same thing happened with the AC on, so I took it and had the code read.  misfire 3 was what I got.  so I changed plugs and wires.  next morning same thing with defrost and same reading.  what would be next?  Thanks!

that should be an EJ22 - but confirm it?

mileage?

any other issues?

 

that's an odd one - so i'll just take some wild stabs:

 

coil pack?  install a used one to test

 

failing alternator if it's load-related?

 

check valve clearance.

Failing alternator was my thought. Easy enough to test. 

 

Start the car, disconnect the battery, turn on the defrost. It the engine quits, you likely found the culprit. 

Not sure how to tell engine type I will include pic. It has 170k miles. I did replace the battery last week. Tried disconnecting the battery but not with a load. I will test that next

so I did the altenator test and when I had the defrost then AC max on it stayed running.  did bog down with no check engine light yet, but still running after 10 mins

after 20 mins of running I got in the car turned on the lights the radio and stepped on the brakes, it bogged down pretty good but never shut off, never got a check engine light. I am gonna look for a used coil pack and try that.  also how would I check valve clearance?

battery cables may be corroded inside - limiting current. other grounds may need to be cleaned-up.

external cables look good but I will definitely explore internal grounds and cables. issue is surely happening under load

96 ej22 has HLAs and are self adjusting as far as valves go.

 

try drving the car with everything on, lights, heat, AC, fan, radio, wipers, dome light, flashers,

turn on the HVAC last.

see if you can cause the problem with something else,

not just the HVAC defrost / AC.

Edited September 2, 201411 yr by johnceggleston

I drive it daily to and from work. The only time I have an issue is with AC or defrost. And if I remember correctly th defrost uses the ac compressor

Not sure how to tell engine type I will include pic. It has 170k miles. I did replace the battery last week. Tried disconnecting the battery but not with a load. I will test that next

That should be an EJ22 (same as my 95 LS).  Can't quite tell from the photo you posted, but if you look down between the power steering reservoir and the alternator it will say the engine model on the block (EJ22 or EJ25).  You can also tell by looking at the valve covers or the number of cam gears on the front.

 

EJ22

 

EJ25:

 

And if I remember correctly th defrost uses the ac compressor

correct.

when you select defrost, it turns on the AC,

and turns off re-circulate.

 

this may be an AC issue,

a wiring issue??

Ok I see it. It says EJ22. Tomorrow I am gonna check out some wiring, grounds ect. Anyone think a possible o2 sensor issue? With loss of power/bogging down. Just a thought. But really only issue with ac/defrost

Maybe the AC Compressor is worn and putting more than normal strain on the engine when it kicks in?  That jolt from the AC clutch kicking in could cause the false misfire reading.  BTW, a transient error like that misfire or the knock sensor will cause the check engine light to stay lit for about 24 hrs after the last occurrence.

After further research, checking for bad grounds, ac compressor, wires, coil pack, I found that a sticking egr valve seems to have been the problem. Sticking open after driving for a bit. I am gonna put more miles on to confirm but I cleaned it and seems to be fine now. Thanks for all the help and if it comes back I will ask more questions. Thanks again everyone.