Odd 2000 XJ Data Log Results

[macidgit]

Attention all PCM/ECU gurus or guru-wannabe's…I have a problem and I need your help!

The vehicle is a 2000 XJ Limited, 4.7 stroker/AW4. Engine has <2500 miles since install. I have been logging data using a Lemur Diagnsotics BlueDriver OBDII connector and iOS software.

Below is an example of the data I've been acquiring, not including O2 voltages because they looked "normal" for this time period. Note that RPM value axis is on the right, all other parameter values can be read on the left axis.

Please take a look at the behavior of ECT, Vehicle MPH and Cylinder 1 Timing between 90-105 seconds (on the X axis). (Just to be clear...the Jeep has never been to 117mph LOL)

Just some questions to start a discussion:

• Can anyone tell me what they believe might be the problem?

• Is this a "real" probem?

• Has anyone else seen this behavior from their data logging results, with these or other sensors (besides O2)?

 

[floyd]

Being a Code Monkey my first instinct is to say: software that wasn't properly bug-tested.

 

[macidgit]

Buggy code in the Lemur software is certainly one possibility...I presume I could monitor one or more of these sensors with a voltmeter and watch for the behavior outside of wiring harness/OBDII bus?

 

[wizardPC]

Communication loss between the bus and the software, and that's how the software interpreted it. Those are all probably max or min values.

 

[mcnamaag]

Something in the engine wiring harness is picking up interference. Everything I see on your graph is related to the same harness. Vehicle speed, temp, etc.

 

[mcnamaag]

I'd start pinning out the harness.