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Fault found after 4 Yrs of diagnosing

posted May 15, 2016 11:10:26 by JamesRoss
OK, so let me start by saying that I have not been trying to find the fault in this car for 4 yrs!
But many other workshops have been trying to find the cause of the customers complaint for that long.

Before taking credit for finding the problem I want to thank Paul for reviving my career as a Mechanic as I was starting to become obsolete given my age and new technologies that are constantly evolving where leaving me behind.

The vehicle.
An Australian delivered Mitsubishi Magna with a 3.5 Ltd V6 engine
The complaint, intermittent misfire at cruise speeds and idle.
Symptoms where consistent with low compression, shorting plugs, coil, wires etc. Possible fuel pressure or injector problems etc etc.

The owner has had all of these replaced in the past in an effort to fix the problem without any success.
The system in this pre 2005 vehicle has limited pids to view in live data, didn't even have fuel trim numbers to monitor so I monitored everything there was to monitor and went for a drive.
This misfire was very apparent but nothing was obvious in the live data that got my attention until I over layed the pids on a graph that can be done with the new Launch pro 3 scanner.

Bingo, there it was.
Crank sensor 1 and crank sensor 2 (as Mitsubishi refer to it) which is crank and cam where showing different RPM values. In most cases there was a variation of 40 to 60 RPM, At times there was a variation of up to 1500 rpm.

Further inspection revealed the problem but I will leave it up to you to think about what the issue was. (Sensor waveforms are good)

In finishing, again I give credit to Paul Danner as without his endless educating I would have retired and swept gutters for a living.

Thanks Paul
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1 reply
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MattWhite said May 16, 2016 14:01:01
Well done mate. Have anything to do with that little disc the crank sensor reads? Can't say I miss magnas! Haha
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