This morning it was REALLY cold. Started the car and it stumbled a bit before the ECU kicked the RPMs up. Idled fine at high rpm.
Then when the rpms started to drop, it started stumbling again. The ECU adjusted and repeated the same process 3 more times before the idle settled and the car seemed fine.
Then the CEL came on

Revved the engine a tiny bit and it was fine. Started driving it and it seemed fine. Pulled OK, no stumbling or hesitation.

Got to work fine with no issue. Went back to my car 2 hours later, it started fine. No stumble, no issue and the CEL was off.

Drove it about 1 mile and parked again, CEL was back on, but I didnt see when it showed up. There were no noticable issues.

Just went on lunch and got the codes read and have a P0300, P0301 and P0303 (Random, Cyl1, Cyl3)


Any ideas/suggestions? Spark plugs? Fuel problem? Maybe intake (I have an AEM CAI)?

 

cant really help you but i kinda have this on and off again cel too.
Came on, i drove to the auto x, as i was staged up, it came on, i ran twice and it turned off.
the code was 1399 random misfire,...i replaced the plugs, and it came on again and went off,...next thing is gonna be a valve adjustment and see if that works.

 

Valve adjustment to start. Then try swapping coil packs around to see if the issue follows a particular one. If that doesnt diagnose it then try the same thing with the injectors. There are already tons of threads out there about this issue.

 

First let me say that while P1399 and P0300 are both random misfire the P1399 is a temporary code which has not hard set in the onboard diagnostic system (OBDII), P0300 has. You note P0300 as well as the cylinder specific P0301 and P0303 so the code is set (repetitive) and correctly note the 1st and 3rd cylinder as setting the code (Note: P1399 is non specific as to cylinder. The computer sees an issue but it is not consistent so no hard code has set-sillyboxer let the code set ). Reset the ECU by either disconnecting the battery for a few minutes or pulling F25 ( under dash driver side) 7.5amp for at least ten seconds. Fire the car back up and listen to the two cylinders in question. If you hear ticking it indicates a coil pack issue. Could be a bad pack but more likely you just need a dab of conductive grease (Pep Boys). The ticking is arcing either pack to plug or inside the pack (coil defect). I can't begin to tell you how many here change out packs un needed. If it still ticks swap a non CEL cylinder pack and see if it follows the pack (as previously suggested). If no ticking I would check and clean the plug tips (plug fouling). With the AEM your getting good air and the OBDII Short Term Fuel Trim (STFT) may be adding too much fuel due to the cold weather if the car has not been driven for awhile (when it was warmer).Could also be the injector (also as noted and a known issue) but the fact two hard set makes me think differently. Just my thoughts.....Good Luck.

Utah

 

yea after alot of money trying to figure out the problem, rebuilt head, it eneded up being a bad injector ring, go down the list of easiest to fix and work your way up, bunch of threads on this