Add another P0304 Cylinder 4 Misfire to the list. STOCK 2006 spec.B
**WHEN CEL TURNS ON**
- Always at cold start
- Very rough at idle, but not dying
- Smoothes out at higher RPM and not even noticeable at boost
- Rough at idle even when warm
- Fluctuates based on temperature and air and humidity
- Always steady CEL accompanied by flashing cruise control light
- Accompanied with low fuel economy
WHEN CEL IS OFF
- Idles fairly smoothly (at first), and gets progressively worse before CEL turns on
- Boost and higher RPMs are good
- STILL low fuel economy (even when CEL was off for 5 months) <--- WHY?
Here's my breakdown:
- Several months ago, CEL came on, but it was /very/ temperamental. Everytime I wanted to take it to get checked out, the CEL would turn itself off (NOT RESET) and stay off for a couple weeks.
- This went on for a few times
- Then, CEL was gone for 5 solid months - never showed. Though, the car did seem like it was running in "safe" mode because I felt less power and definitely a drop in mileage
Recently:
- CEL finally came back on a couple weeks ago, and I took it to my shop. I had the plugs changed recently so they did the coil. Ran nicely with more power and better fuel economy for about 25 miles and then CEL came back on the next day.
- Swapped the injectors and still got the same code, but I still suspect that the injector is bad.
- Did a compression test and got about 135, which is a little low, but not horrible.
- Finally took it to dealer because I wanted to see what they would know. They said that I was /barely/ getting a misfire in cylinder 4. WHAT?! (THOUGHTS ON THIS?) This surprised me. They showed me the 'roughness' or whatever meter and cylinder 4 was at like "1" roughness. They asked me if I was using synthetic. Please.
- I put in some Techron fuel cleaner when I filled up recently just to see if that might clean up the injectors too. Didn't prevent CEL from coming back on after they cleared it on Thursday.
- The dealer is doing something with the intake parts on Monday. I am not sure what that's going to do. Based on the forums, it seems that if it's not a burnt valve (which it's not) then it's fixed by the coil (which is replaced) or the injectors - which has not been done... I haven't seen anyone on here or other forums say anything about the intake with my symptoms (very rough idle and smoothes out at higher rpm with decreased fuel economy). Why are they doing stuff with the intake? Does that make sense for what's happening?
Other:
- My MechE friend who's been taking apart cars since he was a kid said that I should clean the MAF sensor (also suggested to the dealership), but doesn't another code come up for the MAF sensor?
- He also said that it might be the NOx sensor too and it's feeding "lies" to the ECU. But, wouldn't another code pop up for a faulty sensor?
- He said to check if the rattling at idle is rhythmic or erratic. I forgot why... It seems rhythmic though. Thoughts?
Unfortunately, I'm driving cross-country in about a week and need this done ASAP so I was forced to go to the Subaru dealership in Wakefield instead of Cityside in Belmont (because they were very booked).
I have Subaru extended warranty Gold Plus plan or whatever so I have most everything covered.
Any idea what I should tell these Subaru guys to check out next or replace next or clean next?