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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8609
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have a2005 eclipse 2.4. Check engine light with trouble

Customer Question

Hi I have a2005 eclipse 2.4. Check engine light with trouble code random multiple cylinder misfire. Changed plugs, wires, coil packs, cam sensor...any ideas? Any help would be appreciated
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.


Whenever you have a P0300 without any other individual cylinder misfires, it is going to be something that affects the whole engine... meaning you don't have to worry about coil packs, wires, plugs etc as it is unlikely to have all four plugs go out at once, etc.

We are more focused on MAF sensor reading, fuel pressure, fuel quality (old bad gas, contaminated/E85 gas) etc.

Do you have a live data scan tool we can use to see what your fuel trims look like while driving?

Customer: replied 1 year ago.
I currently do not, but I can acquire one and post more info soon...
Expert:  Doug replied 1 year ago.

Sounds good.

I'd like to see your short and long term fuel trim numbers while driving to start with. MAF Hz or gm/s reading at idle and at 1500-2500 RPM would be good too.

Customer: replied 1 year ago. problem started on a trip when I ran the tank way down to empty...the car started missing and idles scan tool shows engine trouble codes but not live data(elm 327 Bluetooth)...although it does show fuel system status and says.."system failure open loop" as if not that's all the info I have.
Expert:  Doug replied 1 year ago.

Out of curiosity, has the vehicle run through more than one tank of fuel since this occurred? Or if only 1-2 tanks, did the initial fill up after running empty get run out too, or was it only partial fill ups after that?

The concern being perhaps you got a tank of bad gas (or mixed with E85 etc) and either have not run it out yet, or if you have been partial refilling it, perhaps it is still diluting.

Customer: replied 1 year ago.
I always fill up and run till empty....the car started missing when the last tank ran out...I stopped and filled up with 93 octane and ran about 1/4 of that tank out.the engine misses to too bad to keep driving. I make this trip often and always stop at the same place for fuel. When the engine started to miss the effect has not gotten better or worse since
Expert:  Doug replied 1 year ago.

Thanks... that is good, so odds are the fuel is not it if you have since put a whole tank of fresh in.
The only correlation I could see otherwise with the running near empty being related to the misfire would be if the tank was run low enough that the pump overheated.... the fuel pump uses the fuel as a coolant which when run low enough causes the pump to run hot which could technically result in damage.
If we can see those fuel trims that will help indicate any relation there without needing to get a fuel pressure tester etc.

Customer: replied 1 year ago.
Ok so I have acquired a scan tool and here is the data I've collected so far.
STFTRM1. -1 TO 1
MAP. 15 TO 16 "HG"
IAT 100
MAF. .50 TO.55 AT IDLE. 1.04 @2000RPM
STFTRM11. -1 TO 1
O2S11. .5 TO.8
O2S12. .06
STFTRM12. -1.6 TO.8
when you say while driving do you mean normal driving at constant speed or heavy acceleration? Are you looking for the min or max?
Expert:  Doug replied 1 year ago.

Thanks. Just in gear and rolling is all that matters in that respect... the reason being if you are sitting still the fuel trims will sometimes stop dead at 0.

That MAF reading is definitely suspect. Everything else looks OK.
The MAF at 2000 rpm we would expect more like 1.7-2.5V.

If you unplug the MAF, does the condition improve some (but not back to normal)?

Customer: replied 1 year ago.
Ok so now that I have a good code reader I have a cylinder 2 misfire code and a injector circuit open cylinder 2...I changed the injector, does that mean the ecu/pcm is bad?
Expert:  Doug replied 1 year ago.

Ah fantastic, that certainly gives us something to work with!

Possibly, but not necessarily. Please unplug injector number 2 and put a noid light or test light between the two pins of the connector. Crank the engine... does the light flash?
If it does not, measure between battery negative and each pin of the connector with the key on... do you have power on one wire?

Customer: replied 1 year ago.
Ok so just finished the test and yes I do have constant power with switch on and I do have a flashing light with engine running
Expert:  Doug replied 1 year ago.

Thanks.... if you have constant power and you have flashing while cranking/running, then the circuit appears to be working normally. Certainly sufficiently that you shouldn't have an open circuit fault. There was no change whatsoever when you swapped the injector?

Just to avoid any confusion, you are working on the second injector away from the belt end of the engine right?

Customer: replied 1 year ago.
I verified the firing there was no change at all, I'm completely baffled
Expert:  Doug replied 1 year ago.

I just mean you are definitely on the second cylinder away from the belts is all.... sometimes people count these backward or count the firing order (1-3-4-2) across the top instead of 1-2-3-4 etc.

If you are on the correct cylinder and you have 12V and ground pulse and the injector is known good, then you most certainly do not have an open circuit... which would mean there is a computer problem at hand as it is seeing that in error. That would be extremely rare though.

Customer: replied 1 year ago.
Ok...the open injector circuit is a new issue on its own.... .the car still misses which is the original issue......should I reset the code and drive ity a while to see if it will show something different or is there a way to test the computer
Expert:  Doug replied 1 year ago.

The way to test the computer for the injector signal is as above.... perhaps that code was set during your testing and was not originally there? If that could be the case, clear the fault and see if it returns.

As for the P0302... if the injector circuit fault doesn't return then we would want to proceed with standard diagnosis.... swap the spark plug with an adjacent cylinder and see if the misfire moves. If it doesn't try a different plug wire and see if it goes away, if it doesn't then compression test the engine and look for a variance on cylinder 2.