nitrousmike108@aol.com

No . I used blue devil some time ago it worked for sure but must of left a film (glue like ) on the outside of the copper.

Wanted to wait until I replied to make sure the car was running with no issues. PROBLEM ended up being a coolent tempature sensor . No codes ...nothing . Seems the radiator sealant or coolent conditioner left a film of glue on the sensor . Never experienced this ever . Removed sensor cleaned it and all is fine . I could not believe a coolent sensor could wreck havoc on throwing a misfire code . Unreal . Some might overlook this when no codes are present. Just my 2 cents . Thank you for all your help . Any explanation on how these sensors operate specifically relating to Subarus is appreciated.

Well I guess I spoke to soon . I reset the CEL all was fine went to fill up and light came on ugg. Not stalling and driving fine .I will do a compression test . My buddy who is a mechanic said since the EGR is on the runner that that might be an issue . Unreal. I am getting 26mpg btw no poping or backfiring .

Well . I must say after going to autozone and exchanging the initial wire set I sprung for the NGK Wire set part number 55004. I now have no more flashing CEL light on initial acceleration and the idle seems smoother . The autozone wires were 7mm and the NGK 8mm. I cannot get over all the time trying to chase down this p0304 code for a wire issue. I even switched the 2&4 wire with the old set and still had a code ? . Maybe the non NGK wires cant take the heat because it just turned summer . Any explanation is greatly appreciated. Thank YOU to all I sincerely appreciate it . Just really bummed at myself for not getting NGK

Many thanks . I'm going to do a compression test . I will let you know the outcome. Thank you so much .

Many thanks . I did not go with OE but will try that . I did switch around the wires ,and that did not help . I did notice an exhaust leak in the rear by the Y that leads to the mufflers? It's a puff puff sound dont know if that could be the cause ?

Hope all is well. Maybe someone could help . I have a 2007 2.5 SOHC . I have a p0304 code . The vehicle has a rough idle . The flashing check engine light goes off as I accelarate and the car drives completely fine . There is the typical external HG leak which I had for 50k + thousand miles . The oil is clean ,car does not overheat, starts fine,runs well with no smoke or bucking . So far I : swapped spark plugs , swapped coils , swapped wires, changed the injector, cleaned egr , sprayed to check for vacuum leaks , cleaned PCV lines . Changed pre cat o2 denso with original equipment denso . Spark plugs are clean . This has me completely stumped. when I pulled the p0304 the LT fuel trim was -15 which prompted me to change the injector. Since changing the injector the car does run better I admit at idle . Any HELP is greatly appreciated. car has 215k . And has been well maintained.