TPS; reads OK until engine is started

alextangent · Post by **alextangent** » Tue Aug 11, 2009 9:18 pm

I've set up the TPS, reads 0 to 100 OK, saved calibration to the unit.

But when I fire up the engine, it sticks at below 8 or 9 and won't go any higher; sticks on the way down at 6 or so, randomly drops to 0.

Coils are about 12 inches away in testing mode. TPS circuit is unshielded 3 wire. I've earthed the TPS on a common earth near the EDIS plug and not on the MJ. Running a pair of earths from the MJ and EDIS to a common point. Everything else works OK (PIP, SAW, RPM, advance etc), but I'm effectively stuck with a 2D map.

Could this be crosstalk?

NITROPIXIE · Post by **NITROPIXIE** » Wed Aug 12, 2009 12:01 pm

Ideally i would put the ground for the TPS to the megajolt unit. Try connecting the TPS earth point to the megajolt earth point and see if this improves things. If that doesn't help then run the earth form TPS directly to megajolt units earth.

Otherwise you may have to check the output of the 5v Voltage regulator and make sure it doesn't change with increased voltage of the alternator charging the battery.

alextangent · Post by **alextangent** » Wed Aug 12, 2009 1:41 pm

Thanks, I think I have some kind of earth problem. I'm going to rewire, as it's just too much sticking plaster over what isn't a terribly good loom (my first effort).

Post by **brentp** » Wed Aug 12, 2009 2:04 pm

Yep, ground is extremely important. For the TPS ground you should reference back to the MJLJ itself.