[Hardline]

Elusive Random Misfire Pissing Me Off!

What has been done thus far. Replaced Plugs, wires, Dizzy cap and rotor, Dizzy itself, CAS, CAS Rotor, and checked all ignition, CAS, and Injector wiring back to the ECM. The only thing left is an intermittent injector. Has anyone else come across a problem this elusive?

Car
2003 GT
Stock intake, Stock Exhaust, Spec Stage 2 Clutch, Fidanza Flywheel, OpenECU Tuning, Prothane mounts.

Was doing this random misfiring before any mods were done.

 

[Bitter]

have you checked compression? made sure the #5 injector is working correctly?

 

[Hardline]

compression is 185 +/- 5 psi on all cylinders

 

[Hardline]

I do not have an injector tester

 

[Bitter]

check the resistance of the injectors, all should be within an ohm or 2 of each other. then listen to each injector with a stethoscope (or screwdriver). they should all be ticking the same.

 

[Hardline]

Well, here's whats odd. It will misfire for only a few seconds. Just long enough to throw a code and set the MIL. The instant the MIL comes on, the misfire disappears.

 

[Bitter]

you need to look at the freeze frame data for when the code sets to see under what conditions its happening.

 

[Hardline]

Ill go and pull it right now.

 

[Hardline]

Load: 84.71
CLT Temp: 163
IAT Temp: 17
RPM: 4340
Speed: 36
Spark Advance: 32
MAF: 114.17
Fuel System 1: OPEN2
Fuel System 2: OPEN2
LTFT B1: -1.56
STFT B1: 0.00
LTFT B2: -3.12
STFT B2: 0.00





Oh, and this time it was a P0303, Two days ago, it was a P0305

 

[Bitter]

so it sounds like you're getting misfires under high load, open loop. since its not always the same cylinder this is going to be a tricky one to track down. i'd suggest PM'ing manybrews either the details of what you've done already, the codes, and the freeze frame data or pm'ing him a link to this thread. he's pretty damned good with mitsubishi trouble shooting.

 

[Hardline]

That is just the most recent freeze frame. Many times it will start misfiring when I am coasting or at idle.

 

[MattS00]

I don't know if this helps, but at one time there was a TSB or recall on certain year cars missfiring. I belive the remedy was an ecu reflash by the dealership.

 

[Hardline]

the only issue is i think i may have lost my oem rom file. when they reflash, do they check the checksum of the rom file?

 

[MattS00]

the only issue is i think i may have lost my oem rom file. when they reflash, do they check the checksum of the rom file?

:scratch: I have no idea what they would do, or any idea what you mean. :lol:

 

[MarkSpyder]

the only issue is i think i may have lost my oem rom file. when they reflash, do they check the checksum of the rom file?

I can only say that when I had them sync my key/s when I swapped to a flashable ECU they were all in my grill about the rom data and whatnot. I don't recall if they specifically mentioned "checksum" but we did discuss the rom file and the fact that the immob and ecu codes/keys did not match...

I highly doubt it would be an issue as long as you explained things to them and were polite about it. When the techs/mgrs helped me out "behind the scenes" I thanked them at ever turn and brought a case of beer to them the next day. They haven't forgotten me since and ask me what I've managed to do with the car so far everytime I call for spare parts. It worked for me...

 

[Manybrews]

is it a GT or GTS?

 

[Hardline]

GT. And btw, it hasnt misbehaved since the 9th

 

[Manybrews]

well, Ill tell you that Ive got nothing but problems with aftermarket parts, regardless of manufacturer.

In fact, i see MORE problems from aftermarket stuff... meaning be sure to use only NGK plugs, and if you're still having issues, try a factory cap/rotor/wire set. They DO work better than aftermarket, even if the aftermarket stuff is supposedly "hi-po".

also, whats the milage?

 

[Hardline]

76k, what about Denso Plugs?

 

[Manybrews]

76k, what about Denso Plugs?

Denso's are good.