djsquare

I have been trying to track down a multiple cylinder misfire for over a year now. My obd2 scanner told me 6/8 cylinders were misfiring, but was not throwing any codes.

A bit of history:
I took it to a performance shop and they ruled out spark and any possible mechanical problems. They suspect it might be a faulty injector, a custom tune or possible aftermarket cam which I don't know about as it's previously owned. They say it's misfiring on #2 the worst, even upon starting it up.

Over the past year I have gotten P0300 (Multiple cylinder misfire), P0102 (MAF low input), P0103 (MAF high input) and P0404 (EGR performance error), P1404 (evap error) with the MAF codes being most recent.

Right now I am throwing 2 codes. P0102 and P0302. I am happy it's throwing codes as it may get me closer to my issue and this confirms the issue is mainly cylinder number 2.

The question:
I just cleaned my MAF yesterday and checked all connections. My code reader gives me a solid reading of 7 g/s at idle and goes up to 30+ relative to the RPMS. I don't have a scanner that does frequency, but with my code reader it looks fine to me.

What could this possibly be? Il proceed with swapping injector 2 and 4 this weekend to see if the misfire moves cylinders.

Thanks for any input - Dustin.

zzcamaro00

could have been a dirty MAF, your into trouble shooting now. you could check the resistance in the MAF compared to another. i have one here at the shop ill check mine you check yours and see whats up. ill return with my findings.

if the maf was dirty it wouldnt read right causing the code. as for your injectors swappin them is a good idea, see if the misfire follows the injector. what is your list of mods? can your scanner read short and long term fuel trims?

djsquare

Thanks for the reply. I sprayed the MAF yesterday with electronic cleaner with the screen in the way, ill try cleaning again from behind.
Ill update you with my resistance reading a bit later when I get a chance. Thanks for the help.
Yes, I can see both fuel trims. Not much variance, -+5% although the right and left vary a bit. One will be plus and the other will be minus usually.

As for engine mods what I can see is: headers, Y-pipe, aftermarket muffler with cutout, tuned out rear 02's with deleted cats, bored TB and CAI mod.
Not too much going on..

zzcamaro00

ah shyt i forgot to test that sensor before i left. must remember to do it in the morning

djsquare

Hah I forgot too.

Where are you measuring the resistance?
The connector wires are 12v, ground and signal (measured in Hertz). So would you be testing the resistance across the sensor wires in the intake?

Let me know I'm all confused haha

zzcamaro00

ill let you know, is it b+? (battery voltage) i think it might be 5 volt reference, signal, ground. i have this thread subscribed with instant email notification, so ill look it up and let you know.

Old Geezer

iTrader: (3)

Maybe try the correct forum??
Tuning and diagnostics may well get more responses.......

zzcamaro00

hmm probably right....

well i measured 13million ohms between the signal and ground pins, thats pin a and pin b

djsquare

Okay, I just measured the sensor part of the terminals (not the connector if that's what you are referring to)
Looks like from A to B is 2 million ohms and from C to B is 150-175 million ohms.
Our readings are a bit off I would say.

Also, after clearing the codes again yesterday, P0102 and P0103 are the only codes showing. So P0103 came back. I really don't get this as my ODB2 sensor readings looks accurate...

zzcamaro00

i couldnt even get continuity at c and b pins, the one i have has just been sitting for a year, heck i took it off a running car

djsquare

I swapped my injectors today, and am clearing my misfire tables by leaving the battery unhooked overnight. Will hope to see the misfire move to the other cylinder.
Also found a loose hose which might have caused the MAF codes, I think it was a PCV valve. It runs on the left side bank 2 along the injectors coming out from just under the throttle body area. Anyways no codes have come back since clearing them (cross my fingers) and hopefully I can get closer to finding my misfire.