Hey everyone. I recently bought my 03 wrx with 78xxx on it. It is completely stock and has never been tuned. When I bought it the CEL was on however it was running great. The previous owner was told from a Subaru specialist that the 4th piston had a sleight misfire but to drive on it. Recently (in the past 3 weeks) the car has had increasing problems with starting and maintaining idle. I am lucky if it starts within 7 tries. It will also cut out when I pull up to a stop light. I am able to keep driving if i keep the rpm above 2k or am out of first gear. When it idles it is extremely rough and feels like the engine is trying to jump sideways. I took it into a mechanic that I was recommended to. After a full day at the shop he believed that the ecu was damaged so we put a new one in. This did not work. The CEL is still on and the same problems are there. According to him all the wiring and timing mechanisms are ok. They also checked the misfire I had been told about and found that the 4th piston is running at around 112 psi instead of the 120 minimum but said that this shouldnt cause the problem. He said he had heard that if the cam is broken it may cause some of the same issues but its a shot in the dark. I had heard that the CEL basically turns the engine into "safe mode" and that if it was left like that it could lead to problems down the road. Could this be connected to that? The previous owner doesn't remember how long ago it turned on but it was before the 60k tuneup. Could this be a faulty CEL? and could it having this on cause the engine to run extremely rough and feel like the timing is off? (I am wondering this because I went on a trip to Oregon a couple weeks ago and the CEL went off for a couple hundred miles in which the car ran amazing and like it should) Prior to the trip I took it into the shop to be checked and they had believed it was the cam position sensor. This turned out not to work however when I left the shop the CEL was off for a while then turned back on shortly after I left.
If anyone can give me any insight into what could cause this that would be awesome.