Andre The Giant

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 ?

Ducman82

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.

Andre The Giant

Cool, so it only deals with idle and WOT, that is good to confirm. I will be changing that TPS when I do the intake refresh/repaint of intake.

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 !

Ducman82

could be she is just not running as rich as she should when un plugged at WOT... and when plugged it, its messed up.

ROG100

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.

Andre The Giant

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 ?

davek9

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

hwyengr

Does the idle switch do anything besides shut down the injectors while coasting? Is there an idle fueling map?

Andre The Giant

But I do have to remove the harness right ? Or can I test from the external end of the harness which sits in front of intake.

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.

PorKen

Idle speed map, and idle ignition map. Fueling comes from the lower areas of the base (aka cruise) fueling map.

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.

ROG100

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.

Andre The Giant

Ok, thank you Roger, that is what I thought, just wanted confirmation to make sure i understood correctly.

hwyengr

Is this what happens when you connect the pins on the circular port at the front? I've been trying to find that thing on the wiring diagram.

Mrmerlin

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

PorKen

When Stan says NO, he means yes.

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.