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Old 10-08-2005, 04:07 PM   #1
Hunt3r
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Default P0303-P0304 Cylinder 3 & 4 misfire detected =(

So I bought my car a few months ago and the guy I bought it from told me that the check engine light is always because the cats are removed. But when I did a few 1/4 mile runs a few weeks ago the fuel cut out and the check engine light flashed. So I took it to Central Florida Turbos to get it tuned and they said that the map was bad although they knew the guy who had tuned it because he put his name on it. But they also said I had some vacuum hose that was disconnected from the turbo because the hose was too short and was probably causing overboosting which would have made the Utec cut the fuel. So magically when they finished tuning the car the check engine light went off on its own, they did not know why but I had disconnected the battery the night before the tune although the CE engine light was still on when I reconnected it and started it back up again the next morning before bringing it in for the tune. So I've been driving the past couple weeks since they tuned it and it has been driving awesome. Although I usually make short trips, I did make a bunch more 1/4 mile runs one night without any problems. Well yesterday during a long drive thru downtown in rush hour traffic and on the interstate and stuff the CE light popped back on again. So today I drove with my friend to the Mazda challenge and when taking off WOT up the on-ramp to the interstate the fuel cut and the check engine light flashed. So I was like aw crap not again and I found an Advance Auto Parts store with a working ODB2 code reader (first 2 stores told me theirs was broken) and it read 2 codes:

P0303 Cylinder 3 misfire detected
P0304 Cylinder 4 misfire detected

I drove it hard again on a few take-offs on both high and low boost to watch my boost gauge but the fuel did not cut again and the CE light did not flash again and my boost was correct for low boost, no spiking or drop off, but the high boost was about 0.5-1psi lower than what it should peak at but it had no spike or dropoff either and maybe it just didn't quite reach peak because I was on highways where going 80mph was pretty fast and I kept having to back off. I couldn't run WOT for very long.

So I checked that vacuum hose again and it seems fine and the only other thing I can think to check are the spark plugs which are a pain in the ass to get to and I can't find anyone with the plugs I want in stock. The guy who owned the car before me told me that he had just put new plugs in the car himself right before selling it to me and he said that he gapped them right but he was no mechanic and he couldn't even tell me how the Utec or boost controller worked. On top of that, he put crappy Autolite OEM replacement platinum plugs in the car. So I'm trying to find some NGK's that are 1-step colder and then I guess I can disconnect the battery to reset the CE light and see if that fixes it but is there anything else I should be checking?
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Old 10-08-2005, 05:45 PM   #2
codered
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Member#: 58033
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Location: Spokane, Wa
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2005 STI
WRB

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Sounds like you are just overboosting. The fuel cut will make you car sense a misfire sometimes. Mine used to do that. I would just run lower boost and be happy. Or get the car tuned by a better tuner. How long have you had those plugs? If they are older than replace them.
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Old 10-08-2005, 06:22 PM   #3
Hunt3r
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Quote:
Originally Posted by codered
Sounds like you are just overboosting. The fuel cut will make you car sense a misfire sometimes. Mine used to do that. I would just run lower boost and be happy. Or get the car tuned by a better tuner. How long have you had those plugs? If they are older than replace them.
The last owner put Autolite platinums in it at about 48k, OEM replacements, and I just don't trust him to have gapped them properly. I was going to buy NGK coppers 1 step colder. The car has 52k miles now. The thing is the car has been running great up until the CE engine light came back on yesterday which is about 2 wks after getting it tuned. And right after I got it tuned I was pushing it really hard to test it out and be sure everything was cool. The night of the tune I did a bunch of 1/4 mile runs and 0-60 runs and it had no problems at all so I had gotten comfortable that it was tuned good and everything was fine until today.
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Old 10-09-2005, 01:37 PM   #4
Hunt3r
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Default

So after looking at old posts and realizing that I can now join the misfire club, I'm starting to think that I have 2 separate problems here.

#1 is the misfire CE light although the car still drives fine usually, idles smooth, and never bogs down. So I guess I need to check my plugs, be sure my ECU is updated, and maybe even eventually get a valve adjustment since people claim that sticky valves are a problem on the 02-03 WRX's and will cause a misfire CE light.

And then #2 I'm overboosting somehow, I have no idea how.....
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Old 10-09-2005, 01:53 PM   #5
kingtut12
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2002 2.5 WRX BY
RIP 02' 2.5WRX PSM

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Are you using an electronic boost controller or MBC?
Do you have an external wastegate?

Check the gain setting in the UTEC parameters also.
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Old 10-09-2005, 01:56 PM   #6
Hunt3r
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Default

Quote:
Originally Posted by kingtut12
Are you using an electronic boost controller or MBC?
Do you have an external wastegate?

Check the gain setting in the UTEC parameters also.
I have a Greddy Profec S in the dash with low boost, high boost, and gain. Unfortunately I don't have a laptop so I was counting on my tuner to set up the Utec correctly...
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Old 10-09-2005, 02:57 PM   #7
hybrid gti 2
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Location: (818) 300k+ ej205 ppg 5mt
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02 vf30 pnp wagon
silver and cf

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try this...

remove the coil packs. notice the three wire connections. twist those slightly. put the coil packs back in. Clear the codes. try that.
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