Stupid DTC P0300

[txhorns281]

OK after my cam install about a month ago I got the infamous P0300 (Random Multiple Misfires) Code. I used to have a Predator unit and would just reset the SES light as it appeared intermittently. But now since I have HPT I was thinking it's time to shut this thing up.

I'm fairly new to tuning and haven't really done anything other than bump my rev limiter but I wanted to know how to fix this problem??? I read a little bit about desensitizing misfire tests but can't really make anything out of the cryptic text I've seen... Someone have a straightforward way to resolve this? I'd rather not disable the code so any thoughts would be appreciated! Thanks in advance!

Will

[Screamn03]

Check out this thread:


This is what I posted there:
I had the P0300 come on with my car every once in a while so I edited:
Edit-> Engine Diagnostics-> misfire-> Max time between events-> low rpm-> changed all values to 32000.

This took care of it and I haven't had a misfire since. Don't really know what it is I actually did (got the info off LS1Tech 3/04) but it has been working great, going on almost a year that way with no problems.

-Mike-

[jimmyblue]

I think you owe it to the car, to at least log all 8 misfires-current
(plus RPM, MAP, fuel-air multiplier, O2s and whatever else will fit)
just to be sure you don't have a single-cylinder misfire problem
or one that's caused by something in the tune. A bunch of low level,
random misfire blips is normal and more will come from a cam & a
lightweight converter. But look for any pattern that might indicate
a problem, before deciding to ignore the whining.

If you see only a low level "ground clutter" then raise the bitch
threshold to maybe 2X the normal-worst, so if something does go
bad later you'll be alerted.

[SSBerserker]

So what is considered ground clutter and what indicates a true issue?

I'm seeing intermittant missing on 1,2,3,4 (0-25ish) and then some heavier missing on 3,4 (sometimes up to 70ish).

I changed the plugs, and one was fouled, but the missing still exists.

[orange_ss]

how do you do that ?

[txhorns281]

Check out this thread:


This is what I posted there:
I had the P0300 come on with my car every once in a while so I edited:
Edit-> Engine Diagnostics-> misfire-> Max time between events-> low rpm-> changed all values to 32000.

This took care of it and I haven't had a misfire since. Don't really know what it is I actually did (got the info off LS1Tech 3/04) but it has been working great, going on almost a year that way with no problems.

-Mike-

Mike, what if my low rpm table is already all set to 32727??? I know I didn't set it that way and I'm the only person that did any tuning after my cam was installed? Never had the 0300 code before the cam either so I doubt another tuner would have messed with it ??? I dunno if my car is missing or not, pretty sure if it is it's nothing to worry about, the car makes awesome power and drives very very well... any other suggestions? Raise the table value up further?

[Screamn03]

I lowered mine to 32000 (was 32767 in the stock tune).

It seems to be some sort of measure of time/counts, like I said before, I'm not really sure exactly what it did but it worked. My best guess would be that by making this value shorter the computer resets its misfire counts more frequently, so it seems to desensitize the detector. Med and High RPM were left alone so if it did develope a misfire (above 1200) it would be caught, although I don't see why I wouldn't feel one SOTPs, but it's nice to know it's there.

-Mike-

[orange_ss]

I think you owe it to the car, to at least log all 8 misfires-current
(plus RPM, MAP, fuel-air multiplier, O2s and whatever else will fit)
just to be sure you don't have a single-cylinder misfire problem
or one that's caused by something in the tune. A bunch of low level,
random misfire blips is normal and more will come from a cam & a
lightweight converter. But look for any pattern that might indicate
a problem, before deciding to ignore the whining.

If you see only a low level "ground clutter" then raise the bitch
threshold to maybe 2X the normal-worst, so if something does go
bad later you'll be alerted.

how do you log misfire for each cylinder ?combination of facts or scanner settings ?

[Screamn03]

how do you log misfire for each cylinder ?combination of facts or scanner settings ?

You want to open up the scanner and then open up the table display.

Right-Click and select insert->engine diagnostics->misfire

You'll see all the different misfire data you can log.

[orange_ss]

cool thanx

[txhorns281]

I lowered mine to 32000 (was 32767 in the stock tune).

It seems to be some sort of measure of time/counts, like I said before, I'm not really sure exactly what it did but it worked. My best guess would be that by making this value shorter the computer resets its misfire counts more frequently, so it seems to desensitize the detector. Med and High RPM were left alone so if it did develope a misfire (above 1200) it would be caught, although I don't see why I wouldn't feel one SOTPs, but it's nice to know it's there.

-Mike-

I'll try that thanks!