the issue with the idle is it keeps revving up to around 1500rpm and stays there . ive reset the adaptive values and it corrects it's self until it cools down or is left over night then reset values again and all is good until next time . i have done this 5 or 6 times and i think if it was a reset issue it should have corrected it self by now as it started after i replaced my o2 sensors. the o2 sensors are reading correctly and all is working ok when it's reset, it just keeps going back to revving for some reason , has anyone else had a similar issue . thanks in advance.

What voltage have you got showing for closed throttle from the TPS. I suspected an intermittent problem with the TPS at closed throttle on a GEMS recently so I thought that I could enlarge the holes and turn it slightly to move the wiper a bit further up the track. That would increase the voltage but I figured that I could then reset the closed throttle voltage to the higher one and it should be fine. It wasn't, idle was high at around the same as you have. It seems that if the TPS idle voltage is higher than 0.9V, it will give high idle even if that is set as the idle voltage. Normal is between 0.6 and 0.8V

i put the nano on today and read the readings before resetting the values , the reading where all reasonably the same except the idle speed reference, it was reading 65280 which is a little hi considering it was only doing about 1600rpm , after resetting it read 742rpm which is what it is suppose to read
the curent throttle pos votage was .69
the stored voltage was .47
after reset
current throttle pos volts .58
stored voltage pos was .58
are these the reading you where referencing Richard.

Yes they are. With a stored voltage of 0.47 and an actual of 0.69, the ECU thinks you have opened the throttle slightly so will open up the idle air valve to raise the revs. It is supposed to learn the closed throttle voltage but it seems that it will only learn downwards so if the stored is higher than actual, it will change but not the other way round. On the Nano, on the next page (I think), you can actually type in the voltage you want.

today i replaced the TPS with a second hand one to see if it makes a difference. the problem was getting worse as it was revving up t 2000rpm and the nano was reading 65280 ,same as last time ,lets see if anything changes, or stops changing , depending on how you see it.

just an update , so far so good no problems, all is still working as it should , lets hope it lasts. 😊

I had a similar issue yesterday. Car drove fine on Saturday to Milton Keynes & back (about 58 miles each way). Then on Sunday it was fine going to shops, but starting to head home the idle went up to 2500-2800rpm. Nanocom reported zero faults and as far as I could tell all values were ok. TPS & IACV seemed to be showing sensible values so got it home. Then it occurred to me to try resetting adaptive values, and the idle instantly dropped back to normal.

I guess I need to do proper checks on the TPS & IACV, etc., Engine has only done 200 miles since I rebuilt it, so the inlet & throttle body is unlikely to be clogged already.

Car did the high idle thing again this morning. It started with idle about 1100rpm, but after a 5 miles drive went up to 2800 again. What's the likely cause of the Idle Reference going to 65280 ?

Cannot figure how to attached files, but they are in this Google Drive folder.

Recording while idle was 2800rpm.
NANOCOM - GEMS.APP - GEMS input file AIR-IDLE

Current throttle pos (V) Stored throttle pos (V) Adaptive air flow (kg/h) Current air flow (kg/h) Intake air temperature (C) Air flow sensor (V) Secondary air status (on/off) Curr. run line position Long term adaptive Idle Short term adaptive Idle Idle speed reference (rpm) Idle air control valve (%) Engine speed (rpm) Gear box retard (%) Calculated load value (%) Gear box status (D/P)
0.72 0.66 -0.85 64.79 5 2.14 4 25 21 58 65280 163 2723 17.6 17.54 N/P
0.72 0.66 -0.85 64.79 5 2.14 4 25 21 58 65280 156 2638 17.6 17.54 N/P
0.72 0.66 -0.85 64.79 6 2.13 4 25 21 58 65280 157 2650 17.6 17.93 N/P

Recording after Adaptive Reset.
NANOCOM - GEMS.APP - GEMS input file AIR-IDLE

Current throttle pos (V) Stored throttle pos (V) Adaptive air flow (kg/h) Current air flow (kg/h) Intake air temperature (C) Air flow sensor (V) Secondary air status (on/off) Curr. run line position Long term adaptive Idle Short term adaptive Idle Idle speed reference (rpm) Idle air control valve (%) Engine speed (rpm) Gear box retard (%) Calculated load value (%) Gear box status (D/P)
0.73 0.72 0 21.59 13 1.42 4 22 34 32 625 54 627 17.2 28.07 N/P
0.73 0.72 0 21.59 13 1.42 4 22 34 31 625 54 650 17.6 28.07 N/P
1.63 0.73 0 39.59 14 1.82 4 22 32 47 625 69 1364 17.2 21.84 N/P
0.97 0.73 0 46.79 14 1.92 4 22 32 47 625 69 1081 17.6 23.39 N/P
0.73 0.73 0 21.59 14 1.41 4 22 32 25 625 46 638 16.79 25.34 N/P

I can't explain why the idle reference is showing 65280 but can explain why it is idling very high. On initially opening the throttle, the TPS signal causes the ECU to open the idle air valve to raise the revs smoothly rather than relying on the airflow through the throttle butterfly. As you give it more throttle, then the idle air valve has a much lesser effect and the airflow through the butterfly takes over. Almost like the accelerator pump on a old school carb setup. The closed throttle reference (Stored Throttle) is showing as 0.66V but the TPS is sending a voltage of greater than that (0.72V). This makes the ECU think you are opening the throttle slightly so has opened the Idle air valve and raised the idle. If you look you will see that the IAV reading corresponds with the idle speed, 156=2638, 157=2650 and 163=2723. At a normal idle, with a warm engine, the IAV should be at around 25-30.

That is why, after a reset, the stored voltage at idle, matches the actual TPS voltage.

ok thanks, useful info mate. Since I posted, I have cleaned the TPS connections, and the GEMS ECU connectors. Voltage seems smooth from 700mV to about 4.5V when I operate the throttle manually (engine off). The TPS appears ok, but maybe there's a dead spot my DMM doesn't spot. Don't have analog meter anymore, so might try my Hantek scope later in the week.

Are the GEMS & Thor TPS the same ? Prices seem to differ wildly.

No they aren't and the GEMS ones are NLA. You will see them advertised as correct for GEMS but the centre where the throttle spindle engages is wrong. They look the same but have a D shaped hole (the same as a standard pot) but they should have two lugs that the edges of the throttle spindle bear against.

Hmm. I guess I should get a used eBay one just in case.

Not a bad idea. I have a friend who buys cars that come up at the right price and either breaks them or refurbishes them to sell on. I'm waiting for him to buy a GEMS (although mostly he sticks to later ones) so I can have the TPS, IAV, green temp sender and a few other bits that are NLA.