TPS problem

[series8217]

I was having TPS issues (ECM thought i was at 7% throttle with my foot off the pedal) causing a high "idle". I bought a new TPS which didn't fix the problem... so I went over the wiring and found that right at the connector the insulation was torn off all the wires and they were badly corroded. There was also a splice there made by the previous owner. Ouch. I found a new connector and spliced it in where the wire was still in good shape. Instantly fixed the problem! Scanner showed a 0% throttle angle whenever I took my foot off the pedal. No exceptions.
Then last night I was working up front so I disconnected the battery. When I reconnected it and ran the car, the TPS problem was back!! I drove around for an hour to see if it would go away but it did not. No error codes.
How/when does the ECM determine the TPS zero position?

[Juglenaut]

RE: TPS problem

Try a new IAC then do relearn procedure, and check the engine coolant temp sensor. Another thing to try is unplug the IAC untill SES lights then plug it back in, unplug the TPS and try to rev it (if the engine is lagging and almost stalling that is good), pull the map plug and the vacuum manifold on top of the throttle body to try and stall it. When stalled keep key on and plug the TPS back in and anything unplugged, and restart it. Drive and relearn at 45mph (I think) for sometime, disconnect the battery...Then what does it do??

If the TPS pops again you may have a manifold leak. Since you modeled your engine you may need a custom memCAL program to offset what more compression you have and to maximize the use of the 13 degree retard timing.

[series8217]

Re: RE: TPS problem

Try a new IAC then do relearn procedure, and check the engine coolant temp sensor. Another thing to try is unplug the IAC untill SES lights then plug it back in, unplug the TPS and try to rev it (if the engine is lagging and almost stalling that is good), pull the map plug and the vacuum manifold on top of the throttle body to try and stall it. When stalled keep key on and plug the TPS back in and anything unplugged, and restart it. Drive and relearn at 45mph (I think) for sometime, disconnect the battery...Then what does it do??

If the TPS pops again you may have a manifold leak. Since you modeled your engine you may need a custom memCAL program to offset what more compression you have and to maximize the use of the 13 degree retard timing.

Dude, please actually read my post. I don't have an idle problem. The ECM doesnt control idle unless TPS is at 0%. There is no problem in the idle circuit. Desired idle is 800 and IAC is still has plenty of steps out. The ECM simply doesnt control idle unless your foot is off the gas.

The problem is: with brand new TPS and wiring, ECM sees 7% throttle when it should read zero.

Again, the problem is simply that the ECM thinks the throttle is open more than it is, even though I have a brand new TPS and just redid the wiring.

1) How does the ECM determine 0% throttle on the TPS, since I imagine the resistances vary slightly between specific instances of the TPS and different temperatures, as well as variances in wiring?
2) What can cause the TPS to not return to zero? I have checked for binding in the throttle cable and there is none. The throttle blade -does- close all the way.

[Juglenaut]

RE: Re: RE: TPS problem

Okay do whatever you want, I am running through a troubleshoot...If you don't want to find it then replace everything.

These cars have a latter effect, where other sensors effect others and yes other sensors can effect IAC. Vacuum effects IAC, The ECM controls the flow through the IAC at all times and all positions of the TPS.

Check continuity from the wires the comes out of the TPS, to the ECM, check ground reference. The only otherway(s) it would show to high of valve angle is either you installed it wrong or the TPS was bad out of the box, or the ECM is toasted, linkages are screwy.

Your engine might have more than usual manifold vacuum.

[series8217]

Again, I am using a scanner to determine the TPS level the ECM sees. TPS level is not affected by manifold air pressure or IAC or time of day. It's a straight signal from the sensor.
The ECM will not idle the motor if you have your foot on the gas. Try it. Step on the gas a little bit when you're at a stop. The ECM does not close the IAC to try and bring the RPMs down because YOU are in control of them with the throttle.
I have gone over the wiring and replaced the bad sections. If I could find out how the ECM determines the 0 position from the TPS I can see if that is where the fault is (i.e. if the ECM is bad or something is binding, etc.).