 TPS on DJet with 2056, Idle circuit |
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| thomasotten |
 Sep 13 2026, 11:44 AM
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#1
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Senior Member  Group: Members Posts: 1,589 Joined: 16-November 03 From: San Antonio, Texas Member No.: 1,349  |
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.
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Replies(1 - 4)
| mgphoto |
Sep 13 2026, 12:24 PM
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#2
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"If there is a mistake it will find me" Group: Members Posts: 1,495 Joined: 1-April 09 From: Los Angeles, CA Member No.: 10,225 Region Association: Southern California |
Idle is controlled by the TPS, and the Pot on the ECU, it has to adjusted for proper function.
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| 914werke |
Sep 13 2026, 12:44 PM
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#3
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"I got blisters on me fingers" Group: Members Posts: 11,746 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest 
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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? |
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| mgphoto |
Sep 13 2026, 01:09 PM
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#4
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"If there is a mistake it will find me" Group: Members Posts: 1,495 Joined: 1-April 09 From: Los Angeles, CA Member No.: 10,225 Region Association: Southern California |
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. |
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| thomasotten |
Sep 13 2026, 02:02 PM
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#5
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Senior Member Group: Members Posts: 1,589 Joined: 16-November 03 From: San Antonio, Texas Member No.: 1,349 |
QUOTE(914werke @ Sep 13 2026, 10:44 AM)  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. |
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