Adjusted the throttle stop last night to get the bastard to idle, the plates were all the way closed, and my non TB mod throttle body, even when the thermo isn't engaged, the plates are open slightly. With the engine cold, I checked TPS resistance, and set it to 1K, and watched it smoothly go to 5K, no problem.

However, I started the car, and let it run.. It hunts around 1500 RPM, which is fine with me, I'll play with that when time permits. Still think I have a vacuum leak anyway.

But after letting the car come up to temp, I checked the TPS resistance. 2K ohms! And when I depress the plunger, it goes from 2K to 500!!! I doublechecked my voltmeter settings, and doublechecked that I had the right wires (green and black).

so.. Normal? Or am I off to Pick n pull?

PaulC

 

I don't think the TPS should go to 500 anytime no matter what. I think that is one of the sure signs that the sensor is bad. You may need the pick and pull; BUT! hold out until one of these other guys confirms your problem. I got my idle to hold at 1k using the throtle stop screw and the air-mix screw. My TPS stays at 1v no problem and my idle does not bounce as of this past saturday. That damn throtle stop screw is a touchy little bitch. One full turn of it changes the idle by like 1k rpms.

 

I probably misread or misunderstood. You do not have the throttle body mod. Right? Right. But you seemingly set the tps with the engine cold(I must be misreading). You have to set the tps with a fully hot engine because the throttle linkage will move as the thermowax comes off its cam which in turn moves the plunger on the tps. So when hot(since you set the tps cold), the reading will be off i.e. not set right.

A lot of folk won't want me to write this, but do the following. Put your meter on dc volts. Find a ground for the negative lead.With the car fully warm and running, all connectors connected, stick your positive lead in the back of the green/red wire. Look at your volt reading. Adjust the tps screw until the reading on the meter reads one volt. Your done. Go wash and wax the car or drink a beer. If you double check this reading in the morning with the volt meter it will read higer than one volt, because the throttle linkage will have moved up on the cam part of the thermowax. I'll read something like 1.65 volts, until the car gets fully warm and then it will return to approx one volt. A .95 to 1.10 volts seems to be a truouble free range for me.

If I misread your post, just ignore the words above, and go get a beer.

 

Nope, got the TB mod, which is why I needed to futz with the throttle stop, the plates were fully closed, and wouldn't hold idle.

See, the problem is that the resistance inverts when it's warm, which doesn't make much sense. When cold (at least the first time,haven't checked it again today), with probes at green and black, I got it to 1K, and smoothly moved up to 5K ohms as throttle was applied. When hot, it started at 2K ohms, and went DOWN to 500 ohms.

I'm sure I was reading the right wires, and I'm sure that's what I was seeing. I'll play with the volts reading, but I'm getting more convinced that I have a bad TPS. Thanks guys.

PaulC

 

Yeah. I thought I must be misreading. Since you did the mod, I don't see what could be moving your linkage, just like you said. I'd still, for grins take a look at the approx one volt at the green/red wire with it connected and see how much it varies from 1V when hot and cold. Kinda sorta wasted your time.

It could be the tps breaking down due being heat soaked and having some internal breakdown. I guess. Heavy on the guess.

 

TTT, thanks for the help Hailers and Samps. Any other input before I head home to futz with it some more?

PaulC

 

My only input is that you will need to ground your negative lead on your dmm—I use the radiator filler neck bolt. Hailers, shouldn't he also jumper his initial set connector?

Brian

 

Sorry about yesterdays post. If its going to 500K its probably bad. Now if it was 0.5K, there's nothing odd about that. But you said 500???? Just wishful thinking on my part.

 

Well, no. I't s going from 2K at full idle, to 500 ohms (.5K) at full throttle. Tha'ts backwards, isn't it?

Wait, I think I'm doing something wrong. I'll post later today.

PaulC

 

Yeah. Wrong end of the pot. I still can't finger out why the setting is moving around on you though. I'm sure someone else will have an idea. Right?