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tps issues

Practical Standalone Tuning

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in my ecu (aem ems4)i see the throtle position is unstable (0.7 to 1.5%) with out touching the pedal when i switc off the engine i see 3.5%and when i starting again is unstable me engine harnness is the universal 96inces from aem

do i have issues with some ground?

Before I suspected a ground issue, I would make sure that it wasn't mechanically reading accurately. When the engine is running, the manifold vacuum will often pull the throttle blade a bit more closed (depend on springs, worn throttle blade shaft bushings, throttle cable, etc). So with the engine stopped, can you make the TPS reading go lower by manipulating the throttle blade?

Next, in older EFI systems, often the sensor resolution wasn't all that great. So what is the smallest voltage it can resolve? 8-bit values (255 steps) over 5 volts will only give you 0.02 volts of resolution. What voltage does the sensor read at 0.7% and 1.5%?

Finally, TPS potentiometers will wear out if vibrated in one location (like idle or WOT) for long enough. Sometimes you can rotate them to a different position and re-calibrate to get a bit more life. But I've worn out plenty of TPS sensors on race cars at 100% throttle, until I switched to using contactless sensors that don't have that problem (but cost twice as much!).

As David said, there may be other factors that are more likely than a ground/power issue, which may be expected to have a much greater variation.

If the engine has a cam', or poor tune, that causes a variation in engine vacuum, that may also affect the load on the butterfly and cause a slight flutter.

If it's an electronic throttle, a slight variation may be resulting from the ECU trying to maintain an idle speed where some other issue is causing the rpm to vary?