i just wanted to post this to see if anyone else has had the same or similar problem in the past. first, the setup:

2002 wrx 2.0 120k miles on the motor
approx 50k miles with the following setup:
vf39, sti pink injectors, walbro, tmic
AP tuned

the problem:

the car ran fine with the above mods for about 3 years, but recently has started throwing CELs and having a very rough idle. the first time it threw the code, i was driving the car normally with a broken b pipe (part between the axel back and downpipe) so i got it welded (good work), but that didn't solve the problem

i pulled the code with my AP and i usually get a p0302 with a p0300, but if i drive the car longer with the CEL on, i will get a p0301, p0303, and/or a p0304.

the weird thing is that the car will idle fine at first, but once it warms up you can hear the misfiring in the exhaust note. it will only throw the light during local driving, but i can drive it on the freeway for very long distances and it won't throw the light until i slow down to city driving speeds. it hasn't thrown the lights at idle

while driving the car, whether the CEL is on or not, i can feel a slight hesitation during acceleration. the throttle becomes smooth again once at speed.

what i've tried:

-changed all the spark plugs, and didn't solve the problem
-switched around all the coil packs to see if one was faulty, and the problem continued
-checked pretty much all vacuum and boost lines and they seem fine
-removed the MAF sensor and cleaned it with MAF cleaner

so i need advice. my best guess right now is that the MAF sensor has gone bad. i also have a suspicion that it could be the timing belt. any other suggestions anyone? any help would be much appreciated.

thanks,
marc

 

Yea a buddy of mine had the same symptoms, miss firing, etc. it ended up that he skipped three teeth on his timing, and had a cracked cam gear! So the timing belt diagnosis could be correct.

 

did he have an aftermarket belt or cam gears?

 

No it was all stock belt and cam gears.

 

how are valve clearances?

 

i sometimes have the same problems dont no y i replaced the plugs and wires runnin up dp cbe sti tmic ap

 

took it to AutoHQ to get the timing belt done, and that didn't solve it although the car drives considerably better. alex did suggest that i might need a valve adjustment. i haven't checked the clearances but i'm considering getting the adjustment done anyway

 

you having compression problems do an cylinder leak down test(do it on an hot engine and cold) most likly piston rings and valves. Does it smoke and i down mean black smoke blueish or white/blue. Do u add oil etc?

 

has ur car been tuned cuz mine was doin that it was runnin to lean and now its running great with the tune (knock on wood)

 

i have the same issue..same setup....I remember when i installed AP on stage one and got the same codes..but when i uninstalled it...the CEL never turned on..When i went on to Stage 3 with vf39..i used the AP and then got it protuned and it still does it..so i don't whats going on..no problems but the CEL..

 

if u guys reuse the injector seals that sit in the tgvs they leak causing an lean condition try to spray starting fluid at each injector and see and difference in idle.