gcross

I believe I have a failing TPS on my '94 Miata/VVT conversion. I previously had a '99 engine with VICS and NB throttle body in this car, so I've had this TPS for awhile, but suddenly it seems to have lost its mind. I'm getting a lot of TPS accel/decal signals on the Engine bits in my logs due to erratic TPS signals, accompanied by the engine stumbling as the injector pw responds. Attached is a datalog, also shown below, I'm running MS3proPNP. Also, when I repeatedly calibrate the TPS I get inconsistent results, sometimes varying by 100 counts or more at 0 or 100% throttle.

I doubt if this is grounding noise given that the TPS value doesn't always track with the engine speed or throttle position but perhaps I'm wrong... I don't claim to be an expert here.

Anyway, any suggestions on the best source for a replacement TPS? I can get a cheap aftermarket version from various online sources OR a used genuine Mazda one from Treasure Coast for about $25. Or I can get a new one from Mazda for >> $100 (ouch!) Thoughts?




* I guess the good news is that I just enabled VVT and the angle appears to be tracking the target fairly well.

gooflophaze

Kia Sephia and I think some Rio's are pretty plentiful in the junkyard and have the same TPS module, though you may want to look at your acceleration enrichment settings and wiring as well. I had my TPS miswired (using Kia pigtail, none of the wire colors matched what I had documented) when I did a similar NB TB on my NA, and it resulted in the response graph looking like



which is what happens when you have vref and tps signal swapped around. Made the car nearly undriveable as it would buck like hell.

gcross

Thanks. Good Kia junkyard tip. I'm leery of the cheap aftermarket replacements.

I did replace the TPS plug when I did the VVT swap and was wondering if I'd wired the new one wrong. However, I just went through the '94 and '2000 wiring diagrams and it looks correct. Here's a diagram of the harness side of the plug. The colors are the '00 version, my '94 colors are different (per the VVT swap thread) but the functions match:


Can the TPS be checked with a multi-meter while out of the car? Anyone know the procedure?

gcross

I found the TPS multi-meter test procedure here: https://www.miataturbo.net/megasquir...6/#post1122797. Thanks to Brain for the how-to. So I checked the resistance between the 5V and signal pins at fully closed and fully open several times. Results were inconsistent and would also jump around while fully closed... I think that settles it, bad TPS.

Thanks again.