Ahhh misfire again...

[Eurosport]

well had a misfire as most of you know back about 5 months ago, changed all 3 coil packs. Then about a month ago had another misfire, and was in the shop with the technician very cool guy for about 4 hrs we couldn't duplicate the misfire car was running perfect didn't get charged a dime, so that was cool. Now again yesterday had a misfire and now car is running perfect again. Except of course the check engine light is still on, needs to be cleared.

Here's the deal, spark plugs are perfect, coil packs very new and under warranty they couldn't go bad, i know there's issues with wire harness on c36's since the design is wires right under the cover of the engine (very hot temp there, and easy for them to move and not make perfect connection).

here's the misfire type that i had and it's all been the same: happened at about 5k rpm, felt like losing power, slowed it down to normal, feels like a little loss in power, when at stop felt like running on 3 cylinders very rough, almost wanting to choke at idle. then stop car restart, still running a little rough, drives ok. stop again restart get it to normal temp, runs perfect, no power loss, exhaust sound perfect.

Now pretty much i'm left with 2 options: bad gas or bad wire harness? Or am I missing totally missing something?

any ideas and also a price range to change wire harness (never had to change that on any car so far) would be appreciated
thanks

[CKlasse]

Originally posted by Eurosport



here's the misfire type that i had and it's all been the same: happened at about 5k rpm, felt like losing power, slowed it down to normal, feels like a little loss in power, when at stop felt like running on 3 cylinders very rough, almost wanting to choke at idle. then stop car restart, still running a little rough, drives ok. stop again restart get it to normal temp, runs perfect, no power loss, exhaust sound perfect.

You car went into limp mode when you hit higher RPM? Check your DTC...

I would look at Air filter just in case.

[Eurosport]

i'll check air filter today
if car would go in limp mode though, wouldn't it stay in limp mode automatically until code is cleared? because now like before is running normal w/out having code cleared yet.

[Rocky]

Million bucks says it's the coil ends. About $10 each and you need 3.

Had the same thing happen to me about a month ago.

Coil ends are known faults, just liek the wiring harness and the MAS on M104's.

The other problem could be plugged EGR in the tube and at the intake end in the block.

I'd put ,my money on the coil ends though.

[CKlasse]

Originally posted by Eurosport
i'll check air filter today
if car would go in limp mode though, wouldn't it stay in limp mode automatically until code is cleared? because now like before is running normal w/out having code cleared yet.

Nah.. engine off few minutes... limpmode is gone.

[kameraguy]

Have you checked your DTCs? I had misfiring issues in the past and the DTCs helped get an idea of the problem. My car had the same symptoms. Rough Idle, and car would "limp" with hardly any power. But after turning off the engine, things would return to normal 75% of the time. So I wouldn't worry about that.

In my case it was loose spark plugs, but in your case it's prob something else since you have already checked them. I'm sure the DTCs would reveal something useful.

[Eurosport]

can't be coil ends though, i just replaced all 3 when i first had this happened and replaced the whole thing not just the ends all coils packs etc.

i have no dtc but now i'm really thinking into getting one
thank god for meeting this nice tech that even worked on Payton's Gwagon, otherwise they'd rape me

i just don't get it though, how could i have a misfire then nothing wrong, shoot even today made some 135mph runs with check engine light still on and car was running perfect. wire harness, or mas, doh forgot to check air filter today, ok going now after i eat.
thanks for the replies btw

[kameraguy]

So the tech you saw was or wasn't able to check for trouble codes?

This type of problem sounds like you would generate something.

When I had my misfiring issues, I had all sorts of codes. It really helped pinpoint the problem.

Just something to consider in case it hasn't been done yet.

[kodiak]

DTC?

~dnm

[Deepchord]

Have you checked your hyper drive unit? It could also be a binary load lifter you know.. It always keeps me from making the jump to lightspeed all the time.

[CKlasse]

Originally posted by kodiak
DTC?

~dnm

Diagnostic Trouble Code Sorry.. i didnt mean to be more confusing. Pretty much its OBDII codes.

[Eurosport]

ok, finally got a chance to plug in auterra

DTC is P0305
misfire cylinder #5

by that code is there any other info i should look for before hitting the shop tomorrow?
thanks

edit:
i'm guessing now that's gotta be one of these problems:
1. wire harness
2. Oxygen senson
3. MAF
4. throttle position senson

anyone know cost on these?