Electronics What's wrong with my TPS? [Throttle Position Sensor]

[Danlenia]

TL;DR

Recently my 01 LS started running poorly, runs fine about 10 sec then stumbles and boggs for about 5, it's kinda random. So I plug TPS in it, the problem still exists.

Hi there,
I'm in need of some ideas. Recently my 01 LS started running poorly, runs fine about 10 sec then stumbles and boggs for about 5, it's kinda random, doesn't matter of its cold or hot. On first start the RPM deep to about 500 then jump back to 800. Occasionally it dies. So I
disconnected the TPS, and behold, it runs amazing. Well, other than the high idle and terrible mileage. Anyway I ordered a TPS, plugged it in, no luck, runs exactly the same. But I was kind of expecting that. So I ordered an new one, but runs like crap again. So I plugged in my cheap OBD2 Bluetooth plug and using torque I looked at the readings.

Slowly moved the throttle from nigh to all and the app shows it pretty linear. No jumps or freezes. Nor during my testing with the engine of, nor during test drives. I was thinking the crank keyway maybe, but the timing is just sitting great, not bouncing or anything. I cleaned the maf with the CRC stuff, changed the air filter, and tried testing the TPS with a multimeter. I got the top wire at 5v constant (switched), middle wire ground and bottom wire variable voltage from 0.74 to 3.69.

Do these look right? I have read a very relevant material (mod edit: link deleted) (anyone interested can go and take a look) and feel that there are some issues. Do y'all think I just have 3 bad TPS, or something else.

Forgot to mention, a few months ago I replaced the cam and crank positron sensors as well as the O2 sensor.

 

[renormalize]

TL;DR Summary: Recently my 01 LS started running poorly, runs fine about 10 sec then stumbles and boggs for about 5, it's kinda random. So I plug TPS in it, the problem still exists.

Maybe you forgot the TPS cover sheet?

 

[Baluncore]

TPS = throttle position sensor
01 LS = ?
Make? Model? Year?

 

[Lnewqban]

What made you focus on that sensor?
It only tells the computer how much air is coming in.
There is a chain of commands to adjust the amount of injected fuel, as well as the timing of the sparks, after that information is received.

It seems to me that three sensors have been providing the correct information, and that the problem must be somewhere else in the chain of events (CMU itself, fuel pump, injectors, sparks strength and timing, crankcase pressure, etc.).

 

[jack action]

So I disconnected the TPS, and behold, it runs amazing. Well, other than the high idle and terrible mileage.

That is because, with no signal from the TPS, the ECU must assume a value, and most likely use one on the richer side. The extra fuel just happens to correct the already lean mixture that tends to drop your engine RPM in the first place.

Troubleshooting videos from post #4 are your best bet. Somehow too much air is getting in, or fuel intake is restricted; most likely in a way no sensors can notice it (i.e. mechanical restriction or failure) since you don't seem to have an error code.

 

[Averagesupernova]

I would suspect a bad idle air control valve. Hang on to your old TPS. Likely the original will outlast a new one.

 

[Tom.G]

I would suspect a bad idle air control valve.

@Averagesupernova made a good suggestion there, check it out.

Also the cam and/or crank position sensors that you changed may not have the correct gap to the shaft they are sensing. They could also have a loose or dirty connector.

Another strange one I ran across:
Many cars these days have variable camshaft timing. This is done with a hydraulic mechanism on their drive gear, and controlled with a solenoid activated hydraulic valve. If that valve fails or sticks you can get some very strange throttle responses, especially if it is intermittent.

Cheers,
Tom

p.s. Please let us know what you find, we like to learn too!