Gems 4.6 low TPS reading, help

[Dasilva]

Hi i'm helping a friend out with sorting an idle issue on his 4.6V8 Gems 90.

We areworking through the sensors and basic setup to understand why its not willing to settle down.

The engine starts and is driveable but the idle cold or warm is hunting around the 800-1500 rpm mark.

If we disconnect the Intake temp sensor it seems to be happier.

Spoken to Nige who kindly sent over an updated manual.

Working throught he basic setup we checked the TPS calibration to find that the closed throttle was "8" and WOT (and we checked the intake) is "44".

According to the guide and Megatune the WOT should be around 250+ nearer the 300 mark.

Thought the OEM TPS snesor was faulty (worked fine in the Ranage rover it was removed from), swaped it for another got the same results

Has anyone got the OEM TPS to out put the expected figures?

Tried swaping the wiring round and the figures just swap round ....so closed 44 WOT 8

Any ideas welcome.

[Bowie69]

Check the voltage at the TPS, and the ground connection as well, should be 5V IIRC.

[FridgeFreezer]

1st off: The wiring:

Green is GROUND and should be wired to the ground pins on the ECU connector.

Yellow is +5v OUT of the ECU.

Red is the signal out of the TPS and should sweep cleanly from 0v to 5v as you rotate the TPS. It's not critical if it starts a bit above 0v and stops a bit before 5v as long as it has a reasonable range and sweeps cleanly without jumps.

2nd point: Don't get too hung up on the TPS reading: the TPS value is not super-critical in itself, the range is 0-255 but that's not so important as long as it moves in the right direction in relation to your foot, the critical things to be sure of are:

- Flood clear mode can be activated above a certain TPS value

- Accel enrichment, Idle control etc. can depend on the TPS being above or below a certain value to dictate what you're doing with your right foot. Absolute values of TPS count don't matter so much as the fact the settings match your TPS's behaviour.

So check if any of these are being activated (or deactivated) by your dodgy TPS reading.

3rd point: Your odd idle may have nothing whatsoever to do with the TPS.

Check that EGO correction is not active at idle RPM and that, with the idle valve blanked off / bunged up / disconnected the engine will start & idle smoothly (if perhaps at the wrong RPM).

Closed-loop idle control is a PID sort of system so can oscillate (AKA hunting) until you tweak the values to suit your engine & idle valve. I had to fart about with mine quite a lot to get it to settle nicely from startup & not stall on arriving at a junction, it's not perfect but it's OK for now.