Strange TPS values when engine is running
 

I put a dial for my TPS on my tunerstudio dashboard today because I wasn't convinced my TPS is giving correct values.

Calibrated TPS.

Ignition on but engine off. Throttle closed 0%, Throttle Open 101%

Engine on. Throttle closed 10%, Throttle Open -22%???

Why would my TPS work fine with the engine off but as soon as it's running the values are all weird?

do you have a vtps?

Yes.

Tps & throttle body off a nb8. I can get full range values between 0-100% when engine isn't running.

I think I had my TPS signal walking on me when I was experiencing bad grounds...or maybe a loss of the 5v ref signal. Check both of these.

OK I seem to be having this issue too. I have a 3 wire vTPS off a 1.6 automatic, Wiring is correct.

Calibrating in TS is no problem. Ignition on, engine off, TPS sweeps from 0-100% without any issue, as seen here.
Attachment 190250

Engine on, signal is a bit jumpy and goes from a low of -30 to about 50-60% max. Checked calibration of zero throttle in TS, no change in value.
http://img.photobucket.com/albums/v6.../tpsissues.png

I measured the voltages at the wires with the engine off and on.

5v reference: engine off zero throttle: 4.96 engine off full throttle 4.97
engine on zero throttle: 4.96 engine on full throttle 5.00
TPS signal: engine off zero throttle: 0.65 engine off full throttle 1.99
engine on zero throttle: 0.65 engine on full throttle 1.20

Why do I have a drop in voltage at the TPS signal wire when the car is on?

Can anyone guide me on the steps I need to do? I did try running a new wire for the TPS signal and ran it straight to the 2L pin. Same thing.
Is it a ground issue? If so, how do I track it down?

Thanks MT :hustler:

I'm having this issue too now. Any of you figure it out eventually?

I'll go one further and mention that I tested my grounds by back probing the ground pin of the TPS harness connector and didn't see any voltage drop between engine off versus engine on. As the OP did, I also tested my 5V reference and again no voltage difference between engine off and engine on.

Any suggestions?

I know it's possible to test outputs using the test mode in tuner studio, but is my best shot at testing individual inputs to try to create a gauge in my dashboard for that specific pin (TPS signal wire) voltage? Is there a better way?

FYI I'm on an MSPNP Pro / MS3, 1.6L '93 with the Flyin Miata vtps upgrade.

Quick update for me personally, I rewired the ground all the way back to the sensor ground on my Megasquirt options port and now it works great! Looks like mine was a grounding issue after all.

In case anyone is still having this issue. I also recently had it and fixed it by switching the wires for 5v and signal like suggested on the below thread. It’s the two outside wires on the connecter.

https://www.miataturbo.net/ecus-tuni...estions-99218/