V7 software issue scanning misfires

[BigTex]

I'm diagnosing a misfire issue and have the PIDs loaded for current misfires and misfire history for all 8 cylinders.

First glance I see the history for Cyl #4 and Cyl #7 are really high. Then I play back the log and watch current misfires. I don't ever see any current misfires for #4. What I do see is #3 has nearly identical current misfires as #7. #7 history climbs incrementally with time as does #4 history.

So "Current #3" and "History #4" belong together. I just dont know which cylinder really has the issue.... 3 or 4???

Take a look:
http://z71.net/misfire.jpg


It looks like this was addressed in the V6 too:
http://efilive.com/forum/viewtopic.php?t=849

[Dirk Diggler]

Swap the coil and see if it moves. My neighbor has a Tahoe a coil went bad and both cylinders were misfiring. I moved the coil pack to another cylinder and it followed making the other adjoining cylinder misfire also. It was also throwong a code for the cylinder that was misfiring to begin with

[Blacky]

It appears GM have at least two different "PID schemes" for misifre cylinder numbers.
Two of those schemes have cyliders 3 and 4 reversed. Depending on the calibration in your PCM, the PIDs will be reversed.

The "fix" made to V6 was due to this same anomaly. Basically the first report of this problem caused us to think we had the PIDs 3 and 4 back to front (when they would have been right for your vehicle) so we swapped them to match the cal that we were investigating.
Neither configuration will be correct while there exists vehicles calibratated in two different ways.

We will need to figure out some way to determine which way around cyl #3 and cyl #4 are for each vehicle, so that the Scan Tool can be reconfigured to cope with both calibrations.

Can you please send a *.tun file from your PCM so we can compare it to other known misfire pid calibrations. Send it to paul@efilive.com

Meanwhile, the most likely explanation for your misfires is that your PCM's calibration (for current misfires for cyl# 3 and 4) is opposite to what the scan tool is displaying. Trust the history count cyl#'s and not the current count.

Regards
Paul

[BigTex]

Email sent with tun file sent. Vehicle is a 2003 Escalade.

[Ninety8C5]

Is it just cyl. 3 & 4 that are swapped ? I just scanned misfires and they are all current for cyl. #5. Was wondering if this is true or really cyl. # 6 ?

[Blacky]

Is it just cyl. 3 & 4 that are swapped ? I just scanned misfires and they are all current for cyl. #5. Was wondering if this is true or really cyl. # 6 ?

It is possible that all cylinders may be different.
What is your vehicle model and year?

If you send your *.tun file to me at paul@efilive.com I can check it and tell you exactly which real cylinder numbers match the actual cylinder numbers reported by EFILive''s Scan Tool.

Regards
Paul

[Ninety8C5]

I have a 98 Corvette, I'm patiently waiting to get a .tun file. The reason I asked is because the misfire sounds like it is on the passenger side, which I believe are the even number cylinders.