Just back from a 1000mile tour of Ireland which was troubled by an intermittent misfire
Brand new NKG Iridium plugs and fresh new Magnecor leads did not fix it.
Symptom is a misfire typically at 2500-3000 rpm starting after a period of some minutes steady running on a light load (straight/level highway - i.e. lowish engine load)
We find that the problem seems to be cleared for a while by giving the accelerator a decent boot and/or "driving it like you stole it" (not really a sustainable solution compatible with retention of licence)
Am suspicious that the TPS (throttle position sensor) may be the cause with a worn bit of track on the potentimeter around mid throttle giving dud info to the ECU...booting the throttle might be temporarily clearing debris on the track...
On return home, have fired up protune but not found any immediately recent historic Diagnostic Trouble Codes other than one reported ~1000 miles ago saying P0122 Throttle Position Low...this was around the beginning of our trip so may mean something and could link to the TPS. The 2/3 other historic codes were much older.
Another oddity was apparent....the info/data record says the engine has done just over 14k miles .... and says it is the original ECU build with no change/update. This bears no relation to the toal mileage for the car nor does it match the mileage since the chassis was changed in 2015 (although closer to this which is around 12500 miles ago). We have not had an ECU change...it is I suppose possible that when Morgan rebuilt the car to replace the chassis, they may have started with a different ECU/wiring loom already installed in the new chassis???
Has anyone any experience on the accuracy of the mileage count in protune??
Looking at the ECM gauges with the angine running, nothing obviously wrong is showing up...and the O2 sensors (another possibility for causing misfires) seem to be reporting fine. However, in connection with my suspicions on the TPS, I was a bit surprised to see the throttle setting at 13% and 0.43V at idle....however, I have no reference to know if this is right or not....
Grateful for any thoughts/suggestions before I start a round of changing sensors and yet another set of plugs/leads.....thanks!
