TPS on DJet with 2056, Idle circuit Options

[thomasotten]

I have a 2056 cc engine running D-Jet. All new lines, harness, everything. The engine has 96 mm pistons and larger valves - 44/36. I had to tune the MPS away from the original factory settings or it was just running too lean. So I richened it up and it runs really well now, checked MPS and adjusted with an AFR gauge. Only worry is my ECU mixture knob has no effect. The throttle position sensor has been rebuilt and calibrated with a new board. I double checked and triple checked the calibration because I know that it won't go into the idle circuit, where the mixture knob has authority if the TPS isn't calibrated correctly. So, the next thing I tried was changing out the ECU. Still acts the same. Idle mixture knob has no authority. So I am wondering, is there something about adjusting the MPS that will cause the computer to never use the idle logic? I know it doesn't have any feedback that you get from an O2 sensor, but I am wondering if signals from the MPS can keep it from going into idle mode.

Thanks

[mgphoto]

Idle is controlled by the TPS, and the Pot on the ECU, it has to adjusted for proper function.

[914werke]

what is the problem you are addressing?
Too high an idle?
Have you smoked your engine to eliminate air leaks that would defeat idle adjustments?

[mgphoto]

TPS needs to be bench adjusted with the throttle body, the ECU “pot” is adjusted with the air screw for idle mixture, they seem to be very picky about this reading in England.
When your car was setup the technician who made the initial adjustments put a detent in the ring around the ECU knob using a soldering iron to indicate the adjustment position.
You need to have the ignition timing adjusted, then after the engine is warm, the air screw is adjusted for idle.

[thomasotten]

what is the problem you are addressing?
Too high an idle?
Have you smoked your engine to eliminate air leaks that would defeat idle adjustments?

The only problem I am addressing is that the ECU knob has no effect. The engine has all new vacuum lines and was smoke tested. TPS calibrated on bench. Question I have is if anyone has found if there are conditions where the ECU knob will have no effect, especially when MPS is adjusted for larger displacement engine.

[nordfisch]

Hi,
did you check the correct electrical function of the TPS?
It has to be adjusted not only on the bench, but on the throttle, too.

Check the continuity between the pins 17 and 47 with the throttle closed.
They have to be 'zero resistance'.



If you have no continuity, loosen the two screws of the TPS and turn it a little bit counter-clockwise until you can feel some resistance.
Fasten it in this position and check the continuity again.

If you still have no continuity, something in the TPS is wrong.

If you have found no problems at the TPS, you might have a problem with the harness.

Regards
Norbert

[Highland]

Curious when you say "bench test" does that mean as a TPS & throttle body assembly or just the TPS?

I've had no effect from the idle knob when the MPS is out of calibration at idle. The knob seems to be a very fine adjustment and if the MPS is too lean for instance, the knob won't do anything. At least that's my experience.

[emerygt350]

Yeah, check your adjustment. I have ended up adjusting them on the car for just this problem. Use a multimeter and make sure that last wire closest to the passenger is responding to the idle position.

[mgphoto]

what is the problem you are addressing?
Too high an idle?
Have you smoked your engine to eliminate air leaks that would defeat idle adjustments?

The only problem I am addressing is that the ECU knob has no effect. The engine has all new vacuum lines and was smoke tested. TPS calibrated on bench. Question I have is if anyone has found if there are conditions where the ECU knob will have no effect, especially when MPS is adjusted for larger displacement engine.

If the ECU knob doesn’t do anything it means the TPS is not adjusted correctly.

[thomasotten]

what is the problem you are addressing?
Too high an idle?
Have you smoked your engine to eliminate air leaks that would defeat idle adjustments?

The only problem I am addressing is that the ECU knob has no effect. The engine has all new vacuum lines and was smoke tested. TPS calibrated on bench. Question I have is if anyone has found if there are conditions where the ECU knob will have no effect, especially when MPS is adjusted for larger displacement engine.

If the ECU knob doesn’t do anything it means the TPS is not adjusted correctly.

Well, that's what I am asking. Can you elaborate on the logic? How does the computer know that the MPS is not adjusted correctly, as you say?

[emerygt350]

No, I am a chronic mps adjuster and no matter how whacky rich or lean I have the mps, the pot still moves the afr at idle significantly in both directions. You just need to adjust your TPS so it is triggering that last wire and the ECU knows to let the pot do its thing.

The TPS is just an accelerator pump so don't overthink it. Just get it so it comes off idle when you begin to move the throttle and you are good. Currently it appears to be adjusted so it doesn't go into idle mode.

[Dave_Darling]

First thing to do is figure out which pins are the "closed at idle" pins. They'll be shorted to each other when the throttle is closed.

Second thing to do is make certain that they are actually shorted to each other when the throttle is closed. A multimeter will do that, or a test light.

Another test you can do after the above: Back-probe the TPS connector with some of those metal T pins. Get into the two connectors for the idle position circuit. Short them together and see if the ECU knob changes the mixture at all.

It may be possible for your base mixture to be so far out that the knob won't have an obvious effect, particularly if you're not measuring the O2 content in the exhaust. I'm not sure, frankly, but I would expect in that case that the car would run poorly anyway.

--DD

[mgphoto]

what is the problem you are addressing?
Too high an idle?
Have you smoked your engine to eliminate air leaks that would defeat idle adjustments?

The only problem I am addressing is that the ECU knob has no effect. The engine has all new vacuum lines and was smoke tested. TPS calibrated on bench. Question I have is if anyone has found if there are conditions where the ECU knob will have no effect, especially when MPS is adjusted for larger displacement engine.

If the ECU knob doesn’t do anything it means the TPS is not adjusted correctly.

Well, that's what I am asking. Can you elaborate on the logic? How does the computer know that the MPS is not adjusted correctly, as you say?

The factory manual has the procedure, throttle body and tps off the car, the picture presented is the way to set it up. Connect the correct pins and rotate until the multi meter reacts, tighten the set screws, then adjust the air screw and the ecu knob, if you don’t have a AFR meter or idle adjustment meter, adjust for 1000 rpm with the ecu knob at the detent.

[emerygt350]

With a 2056 be prepared not to be at the detent. Depending on the tune with mine and how advanced the timing is it makes more sense to get the car to 900 or so at idle and then use the pot to get a nice steady idle. Normally that means somewhere between 13 and 14 on the AFR. You have an aftermarket cam as well, so you can't stick with regular djet setup.