Please define, total misfire count and history.
Thread Starter
Joined: May 2004
Posts: 1,080
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From: Elgin, Illinois
Please define total misfire count. What do the #s mean? My misfire count current seems to go from 0-4 or so mostly at idle ( have one cell that says 10259!! is that an error? If not, I logged current misfire count and added up 10000 lines of data. Out of these 10,000 lines I have a total of 1,425 cyl 1 misfires, 0 cylinder 2, 0 cylinder 3, 1,564 cylinder 4, 19,814 cylinder 5 (Thsi is where that 10,259 cell is), 152 cylinder 6, 3126 cylinder 7 and 3045 cylinder 8. Now this is adding up every cell in each cylinder column (cyl1-8)(10,000 rows). Could this be an indication of plug/wire problems, or is this normal??
My car is pretty much stock, any input is appreciated.
Thanks
dave
My car is pretty much stock, any input is appreciated.
Thanks
dave
Last edited by TT_Vert; Jul 3, 2004 at 08:14 PM.
TECH Resident
Joined: Jan 2002
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From: USA
Info about misfire :
http://teamzr1.com/cgi-bin/ultimateb...c&f=2&t=000022
If you were getting real or false misfires then you also would be getting DTCs for that and if it was multi misfires also the SES would be flashing unless someone has derated or turned off those DTCs.
Your scanner may be showing the wrong PID and instead showing the misfire revolution counter
http://teamzr1.com/cgi-bin/ultimateb...c&f=2&t=000022
If you were getting real or false misfires then you also would be getting DTCs for that and if it was multi misfires also the SES would be flashing unless someone has derated or turned off those DTCs.
Your scanner may be showing the wrong PID and instead showing the misfire revolution counter
Thread Starter
Joined: May 2004
Posts: 1,080
Likes: 0
From: Elgin, Illinois
i was loging the rev count as well so that isnt it. Any idea how many misfires are needed to light the SES light? Im just looking for some input on what the above #s should be or a range
dave
dave
Thread Starter
Joined: May 2004
Posts: 1,080
Likes: 0
From: Elgin, Illinois
I ohmed my wires and they checked out and put in new plugs, now this is what my total misfire count is after 10,000 cells. (im using autosum for total misfire count for entire cylinder)
From cyl 1 over to 8 I have :
Cyl 1: 3122
Cyl 2: 0
Cyl 3: 0
Cyl 4: 3252
Cyl 5: 314
Cyl 6: 0
Cyl 7: 578
Cyl 5: 878
Does this indicate any problem or is it normal??
From cyl 1 over to 8 I have :
Cyl 1: 3122
Cyl 2: 0
Cyl 3: 0
Cyl 4: 3252
Cyl 5: 314
Cyl 6: 0
Cyl 7: 578
Cyl 5: 878
Does this indicate any problem or is it normal??
You probably should not be summing misfires, the misfire count is already a sum.
The current misfires per cylinder is the sum of firing events in the last 200 engine revolutions that were considered by the PCM to be misfires. The Jendham's manual that I have also states: that the value transmitted by the PCM to the scan tool is twice the actual amount - so if the scan tool says 50 then the number of misfires would actually be 25.
I would assume that the value should not go above 200 per cylinder per 200 revolutions (100 actual misfires) - since you can't have more than 100 firing events per cylinder in 200 engine revolutions.
If you're only seeing 3000 misfires in 10,000 samples that might be ok.
Assuming average rpm=3000 and the scan tool is sampling at 10 samples per second:
That's 50 revs per second for 1000 seconds, that's 50000 revolutions, which is 250 lots of 200 revolutions.
3000 divided by 250, is only 12 misfires (actually 6 if the PCM is reporting twice the number) per 200 engine revolutions.
I'm not an EFI expert, anyone care to jump in and say whether that is an acceptable misfire rate or not? Or maybe a math guru can correct my math if it is wrong.
As for misfire history:
The PCM will not begin to record misfire history until a misfire code is set and at least 195* misfires have been detected in the last 200 engine revolutions across all cylinders. History data is updated every 200 engine revolutions.
*I have not confirmed that value. It is from a description in one of the Jendham's manuals. It may or may not be accurate.
Regards
Paul
The current misfires per cylinder is the sum of firing events in the last 200 engine revolutions that were considered by the PCM to be misfires. The Jendham's manual that I have also states: that the value transmitted by the PCM to the scan tool is twice the actual amount - so if the scan tool says 50 then the number of misfires would actually be 25.
I would assume that the value should not go above 200 per cylinder per 200 revolutions (100 actual misfires) - since you can't have more than 100 firing events per cylinder in 200 engine revolutions.
If you're only seeing 3000 misfires in 10,000 samples that might be ok.
Assuming average rpm=3000 and the scan tool is sampling at 10 samples per second:
That's 50 revs per second for 1000 seconds, that's 50000 revolutions, which is 250 lots of 200 revolutions.
3000 divided by 250, is only 12 misfires (actually 6 if the PCM is reporting twice the number) per 200 engine revolutions.
I'm not an EFI expert, anyone care to jump in and say whether that is an acceptable misfire rate or not? Or maybe a math guru can correct my math if it is wrong.
As for misfire history:
The PCM will not begin to record misfire history until a misfire code is set and at least 195* misfires have been detected in the last 200 engine revolutions across all cylinders. History data is updated every 200 engine revolutions.
*I have not confirmed that value. It is from a description in one of the Jendham's manuals. It may or may not be accurate.
Regards
Paul
