TPS value at idle rises when hot

[idt512]

After 15 mins of driving my TPS value rises to about 1-3% and the cars idles around 1200 RPMs... Ive checked my TB and it is NOT sticking and is fully hitting the stop screw. When I shut the car off I close & open the throttle and view the TPS range with my SAFC and everything is normal 0-100%, but as soon as I start it up again (car still hot) it will be back to 1-3% and idles around 1200 RPMs again. The first 20 minutes of driving everything is perfect. Im leaning toward a faulty ECU...but what do you guys think?

Car has no CEL

 

[bboyalan]

Have you ohm-tested your TPS and ISC/IAC yet?

 

[Silver 95 GST]

That's normal.

When you run your engine it heats the cable housing around your throttle cable effectively making you cable shorter.

Who cares what the TPS reads when cold. Most of your driving is when the engine is hot. So adjust your TPS(rotate it) so that at hot idle your TPS reads 0%. This will ensure that your ECU goes into idle mode, which will prevent idle surge. Also when in gear, rpm above 1200rpm and TPS=0 your ECU will turn off injectors saving you gas. (as described below). Good luck

http://www.dsmtuners.com/forums/articles-miscellaneous/254223-how-save-gas.html

 

[bboyalan]

That's normal.

When you run your engine it heats the cable housing around your throttle cable effectively making you cable shorter.

Who cares what the TPS reads when cold. Most of your driving is when the engine is hot. So adjust your TPS(rotate it) so that at hot idle your TPS reads 0%. This will ensure that your ECU goes into idle mode, which will prevent idle surge. Also when in gear, rpm above 1200rpm and TPS=0 your ECU will turn off injectors saving you gas. (as described below). Good luck

http://www.dsmtuners.com/forums/articles-miscellaneous/254223-how-save-gas.html

The last time that I checked, heat creates expansion because of the molecules moving faster. Cold = dense[r]. If I am wrong, then a lot of my professors need to be fired.

Anyway, read this too:
Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

For the 3/S, it is recommended to have the "cold idle" set at ~14-15% throttle. Personally, I have 10.5%. The ISC in conjunction with your BISS setting will regulate your idle thereafter. How much slack is in your throttle cable? It might be very tight. Test your TPS for continuity!

 

[Silver 95 GST]

Heat does cause expansion, (except for ice to water, which shrinks).

But in the case of the throttle cable if the cable HOUSING gets longer that's like making the cable shorter.

 

[bboyalan]

Haha yeah, silly water exception.

Gotcha though. I misinterpreted that for solely the cable.

 

[idt512]

That's normal.

When you run your engine it heats the cable housing around your throttle cable effectively making you cable shorter.

Who cares what the TPS reads when cold. Most of your driving is when the engine is hot. So adjust your TPS(rotate it) so that at hot idle your TPS reads 0%. This will ensure that your ECU goes into idle mode, which will prevent idle surge. Also when in gear, rpm above 1200rpm and TPS=0 your ECU will turn off injectors saving you gas. (as described below). Good luck

It is NOT normal, you overlooked the section where I said I have verified the throttle to be fully closed since it is hitting the stop screw, it is NOT a cable issue. Also the TPS is already rotated to max for it to read 2% when hot, im only getting 97% at WOT from doing this. As soon as I shut the car off it reads fine 0%. And that is the reason im thinking its the ECU

 

[greggs]

hey guys is it normal when you start the engin every morning thers a rumbling sound like a carburator in your 2g

 

[idt512]

hey guys is it normal when you start the engin every morning thers a rumbling sound like a carburator in your 2g

Your question has no relation to my TPS problem

 

[bboyalan]

Wait wait, your list of modifications says that you have a Palm Logger. What do your low fuel trims look like? Your timing? It might be related to your tune with the upgraded fuel setup. Just a thought. I only say this because it's fairly common to have idling issues with larger injectors without timing control.

 

[greggs]

sorry man im just new here