TPS and IAC not staying where they're set to

[Boston GN]

After swapping out the plenum and TB gaskets and swapping out some vacuum lines due to some leaks, I reset the computer and adjusted the IAC and TPS sensors. Had the TP at .44 and IAC was hanging around 13 at warm idle. Took the car out for a ride and the TPS changed to 52 at idle and IAC 0 and yes, the TPS sensor is tightened down and can not move. Not changing anything, I went out for another ride and when I returned home the TPS was at .46 and IAC within a normal range. This has happened multiple times where I get the TPS and IAC within their typical set range and after a quick ride, the TPS will change to 50-52 by itself
Any ideas what could be happening? Obviously not too concerned with the IAC changing much, it's more the TPS sensor doing the wacky thing it's doing

 

[TRICKSIXPA]

What brand of TPS are you using most of the aftermarket brands have hard springs and can be a bitch to get to stay put. Some others have different moldings that don’t hold the screws on correctly. I try and use an AC Delco on these.


Sent from my iPhone using Tapatalk

 

[Boston GN]

I believe it's a standard: http://www.highwaystars.net/sensor-throttle-position-25036663-s/

I physically can't move the sensor once it's tightened down. I verified that the throttle blade is completely shut also when it jumps up to .50-.52. I might just replace it anyway. Cheap insurance

 

[750H.P.V6]

Have you checked to see if your system voltage is stable? I've seen instances where something like a bad volt booster can cause over charging. If the input voltage to the TPS changes the output will also. If the TPS voltage goes over .5 volts at idle it will result in a high idle and as a result your IAC will be high.

Neal

 

[dennisL]

Check your TPS with a multimeter. Leave the TPS connected and push pins into the connector next to the wires. Clip the meter probes to the pins. Use the TPS black wire (ground) for the meter negative probe. Electrically this is the same as the engine block but it comes from the ECM so use the same ground the ECM is using. The top grey wire should be +5Vdc which also comes from the ECM when the ignition is on. Measure it with key on, engine off and with key on, engine running. The +5V should not change.

If the +5V is okay, then move the meter positive probe to the middle dark blue wire. This is the TPS voltage to the ECM. The voltage here will always be about 0.02V higher with the engine running so keep this in mind when adjusting the sensor.

 

[earlbrown]

Try this test.....

Slowly give it gas, then slowly let off... Take note of the TPS and IAC.

Then give it some gas and let the throttle snap shut quickly. Take note of the TPS and IAC.


If it consistently acts right when you let the throttle snap shut you've got something keeping the throttle blade off the stop screw. the cruise control cable not having slack can do this.


If your TPS ranges change at random while the blade is firmly against the stop, you either have a TPS output issue, or a +5V TPS feed issue. I kinda doubt that because you posted when the TPS is high the IAC is 0. Which means you were probably ideling fact from a partially opened throttle blade, and the IAC closed off trying to bring it down.

 

[pacecarta]

replace the ecm ..sounds like the 5v source is drifting

 

[750H.P.V6]

I think Earl is on the right track and I misread what you originally stated.

Neal