AdamSS

iTrader: (3)

OK - major mods F10 cam (228/228 LSA 112) and boltons.

Car runs great, and tuned using hptuners (no wideband)

Pretty much I get PO300 random misfire at low rpms error code, but only when MAF is enabled. When I was tuning in SD mode without MAF, code never popped out. I have the SLP Z06 maf, and I had tables tuned for it....
I also had the low rpms misfire table values "desensitized" I think to 32000

I just don't understand why enabled MAF would cause Po300 ??

Any help would be appreciated....
Thanks

Michael02hawk

iTrader: (26)

After that CAM install, did you perform a crank re-learn?

AdamSS

iTrader: (3)

How is that done ?

Is it the same as PCM re-learn ?

GuitsBoy

iTrader: (4)

Disabling the MAF will keep the computer from keeping track of all misfires.

RedHardSupra

iTrader: (1)

huh? what does disabling maf have to do with misfire detection?

GuitsBoy

iTrader: (4)

A few months ago I could feel a misfire but when I logged my misfires, all my counts were 0. I tried lowering my threshholds but nothing would get them to read. On a whim, I plugged in my MAF again and presto the misfire counts began clicking away. I was able to trace which sparkplug wire wasnt connected securely.

RedHardSupra

iTrader: (1)

so you're saying that the misfire is real and that misfire detection gets disabled in SD?

Adam, start scanning for individual misfires, let's see if it's real (and is it just bound to a certain cylinder) or it's just sensors being oversensitive

GuitsBoy

iTrader: (4)

In my case, thats correct. I figured perhaps variations between MAF and dynamic airflow calculations were compared in addition to instantaneous crank speed when detecting misfires.

I knew I had seem my misfire counts ticking away happily in the past (individual counts as well as total). I was surprised when I wanted to trace back my misifre to a cylinder and nothing was counting. Plugging the MAF back in made them start counting. I usually have a handful of misfires on every cylinder (heads/cam) but number 6 was many times what the others were. I unplugged and replugged the wire in and the misfire went away.

RedHardSupra

iTrader: (1)

hmm..i'm quite sure i've seen misfire counts work in SD, now if i could just dig it out from 1.5gigs of tunes and logs...

AdamSS

iTrader: (3)

Marcin, the code is generic.... PO300 - "RANDOM low rpm misfire"
It's not bound to specific cylinder. If it was, I'd suspect bad spark plug wire.... I really have no idea what triggers it....
I'll go over the spark plugs again.... maybe I have two plugs that are not pushed all the way in, hence triggering "random" misfire...random as in "two or more cylinders" ???

RedHardSupra

iTrader: (1)

you can scan for individual misfire counts on each cylinder.
different things can show up as misfire, for example i had two cars where there was a misfire on 7/8 and it turned out to be just the injector wasn't fully pushed in (not 'clicked'). so the individual misfire counts are really to be used as locators of problems, not something that tells you a definite problem.
with your car, i'd have no idea what it'd be, as it's damn solid and it scans perfect no matter what we throw at it. but a good test nonetheless. the crank sensor relearn would be a good thing, but i'm not sure if HPT put it back in the software yet (they had it in 1.x but pulled it out for 2.x for some unknown reason)