Wiring harness for TPS on MY85
#1
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Wiring harness for TPS on MY85
This spring I replaced the TPS wiring harness because of a broken connector at connection point just in front of the intake.( So basically the car was running with a disconnected TPS wiring harness prior to repairs). When I test drove the car and tried the WOT, the car choked almost to a stop every time I would floor it and that scared me because that did not happen prior to the repairs.
So I went back to troubleshoot, and figured the TPS harness was the only different thing in the equation, so I decided to disconnect it and test the car again at WOT, and all was working as previously, the car was accelerating as normal on WOT.
So I figured the TPS is bad, but did not change it yet, next year when I do the intake refresh because of location and ease of getting to it.
The one thing I don't understand is, is the TPS not a crucial piece in the functionality of the idling and WOT responses ? Yes my idling is a little erratic if not started for a few days, but then it returns to being stable.
Doesn't the TPS connect to the LH or EZH computers through the TPS harness to run through the computer for proper settings ?
Can anyone shed some light ?
So I went back to troubleshoot, and figured the TPS harness was the only different thing in the equation, so I decided to disconnect it and test the car again at WOT, and all was working as previously, the car was accelerating as normal on WOT.
So I figured the TPS is bad, but did not change it yet, next year when I do the intake refresh because of location and ease of getting to it.
The one thing I don't understand is, is the TPS not a crucial piece in the functionality of the idling and WOT responses ? Yes my idling is a little erratic if not started for a few days, but then it returns to being stable.
Doesn't the TPS connect to the LH or EZH computers through the TPS harness to run through the computer for proper settings ?
Can anyone shed some light ?
#2
Wiring harness for TPS on MY85
That model of tps has an internal WOT and idle switch. That's it, it's not a progressive "rheostat" style like other cars. Sounds like the switch adjustment is out/bad switch. Now why it's working ok ish without is odd.
#3
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Yes the fact that it's working without it, baffles me since I thought it was a crucial part of the system which instructs the computer on the mixture of fuel and more !
#5
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Andre check the continuity on all three wires end to end on the TPS harness. We had some earlier this year where the wires were crossed from the manufacturer.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
#6
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Thank you Roger, I will do this once I store it for the winter. All I do is connect the positive to one end of the harness and the other to the other end, same pin and put the meter on Ohms ?
#7
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There are 3 wires, one is ground.
1 closes to ground at idle
1 closes to ground at WOT
Middle peddle is cruse settings, neither switch closed, between the three setting the computer selects one of 3 maps.
All can be tested w/o removing the switch
1 closes to ground at idle
1 closes to ground at WOT
Middle peddle is cruse settings, neither switch closed, between the three setting the computer selects one of 3 maps.
All can be tested w/o removing the switch
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#9
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Roger is suggesting testing continuity which I assume I have to do by checking using the harness and connecting each prong of the Ohm tester to the same pin on each end, correct ?
Then the test you are referring to can I do from the external harness connection ? If so where do I position my connectors of the meter, what setting am I measuring and what to expect.
Sorry for all the questions, but I am not very knowledgeable yet on all methods to use a metre.
#10
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The ignition map helps the ICV center the idle speed at 680, but is much faster acting. (High advance below 680, lower advance above.)
Idle and WOT both true = CO/idle set mode.
#11
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Andre remove the harness and test for continuity one end to the other. We had some harnesses that had one of the wires crossed. Pin 1 should go to pin 1 and so on. Use the continuity position on the ohmmeter and it should beep if you are good.
#12
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Ok, thank you Roger, that is what I thought, just wanted confirmation to make sure i understood correctly.
#13
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#14
Team Owner
HWY...answer is NO.
The circular port jumper is used to remove the idle speed controller from the system ,
so the base idle can be set via the throttle body .
and then the blinker tool is used to set the mixture
This has nothing to do with the TPS.
The common fail point for the TPS is the connector cracking apart where its mated to the car side of the harness at the top of the water bridge.
Remove the short TPS harness from the TPS and the car side of the harness and check it as Roger has advised.
Also inspect the TPS to see if the unit may be filled with oil
The circular port jumper is used to remove the idle speed controller from the system ,
so the base idle can be set via the throttle body .
and then the blinker tool is used to set the mixture
This has nothing to do with the TPS.
The common fail point for the TPS is the connector cracking apart where its mated to the car side of the harness at the top of the water bridge.
Remove the short TPS harness from the TPS and the car side of the harness and check it as Roger has advised.
Also inspect the TPS to see if the unit may be filled with oil
#15
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C is ground
B is the WOT input (shared with the TPS)
A is the O2 sensor state, rich/lean from the LH
For the LH to go into CO/idle set mode the TPS has to be at idle. Bridging B and C makes WOT true.
This disables LH idle control and O2 sensor correction. (EZF goes to WOT map = no ignition advance idle correction)
If the TPS or wiring is bad and the idle input is not going to ground then the CO mode won't activate.