False AE triggers - SOLVED (I think)

[Philip Lochner]

I can quite rightly say that I have been struggling with false AE triggers for YEARS!! (I did my first MS2 install in 2006)

All the time there is absolutely no evidence in the TPS tracklog (flat lines) to serve as cause for AE to trigger and yet it has been been a bugbear in my MS experience. I can not understand how AE could trigger if there was no TPSdot data to serve as cause for it to trigger - unless TPSdot figures were generated in the firmware not visible via datalog figures.

Symptoms on the car were, idle speed dipping occasionally (with corresponding AFRs going briefly pig rich in sync with the AE triggers) and while driving the AFRs also dipping to rich every time AE triggers. This did not happen consistently either as sometimes it would be fine and other times be a bother. I also found this seemed to happen more at light throttle than at large throttle openings.

Well, I think I have finally "cracked" it by installing a 100nF in C8, a 100kOhm resistor in R9 and a 220nF in C9. I've done this on my Jensen Interceptor and my Jag XJS and both seem to be behaving now. On the Jag I have not made any changes to my TPS based AE via TS.

[trakkies]

TPS usually wear first towards the closed throttle position. As there is obviously far more use at that end. Did you check the TPS properly for noise? If your Jag has the same Lucas TPS as my RV8, they are notorious for this. I'm not sure noise would show up on a log. I replaced mine with a Vishay unit which uses a conductive plastic track rather than carbon, and no more problems.