: High Idle Causes



99Classillac
02-01-10, 10:55 AM
Hi guys! I just wanna post this for people with idle problems. If you have been reading my other posts, my DTS is a idle monster. After reading on here, it got me brainstorming and I thinks I found the problem. High idle can be cause by lots of things, but this may be an overlooked cause. The TPS(throttle position sensor). Vacuum leaks, IAC valves, and this. I couldn't find a vacuum leak. I had replaced the plenum a couple of months ago and I am confident in my work. I didn't want to buy an IAC valve. Too much $$$. I was thinking maybe my EVAP purge valve was stuck open, but I doubt it. After reading around on the web and after throwing a TPS code, I'm confident it is this. My car has been iding perfect for a day now. Knock on wood... But here

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. The sensor is a sealed unit and cannot be repaired only replaced. A TPS may fail gradually leading to a number of symptoms which can include one or more of the following: -

Poor idle control: The TPS is used by the ECU (http://www.cadillacforums.com/a/ECU) to determine if the throttle is closed and the car should be using the Idle Air Control Valve (http://www.cadillacforums.com/a/Idle_Air_Control_Valve) exclusively for idle control. A fault TPS sensor can confuse the ECU causing the idle to be erratic or "hunting".


High Idle Speed: The TPS may report faulty values causing the engine idle speed to be increased above normal. This is normally found in conjunction with a slow engine return to idle speed symptom.


Slow engine return to idle: A failing TPS can report the minimum throttle position values incorrectly which can stop the engine entering idle mode when the throttle is closed. Normally when the throttle is closed the engine fuel injectors will be deactivated until a defined engine RPM speed is reached and the engine brought smoothly to idle speed. When failing a TPS will not report the throttle closed and fueling will continue causing the engine to return to idle very slowly.


Engine Hesitation on Throttle Application: The TPS is also used by the ECU (http://www.cadillacforums.com/a/ECU) to determine if the driver has applied the throttle quicker than the Manifold Air Pressure sensor can read. The fueling is adjusted acordingly to cope with the sudden increase in air volume, however a faulty sensor can cause the ECU (http://www.cadillacforums.com/a/ECU) to ignore this data and the engine will "hesitate" when applying the throttle. In extreme cases with the engine at idle, a sudden application of full throttle can stall the engine.


Engine Misfire: A fault TPS can report values outside the deined acceptable range causing the ECU (http://www.cadillacforums.com/a/ECU) to incorrectly fuel the engine. This is noticable as a slight misfire and can trigger the misfire detection software and/or Malfunction Indicator Lamp (MIL) light on the dashboard. Extreme cases can cause excessing misfires resulting in one or more cylinders being shut down to prevent engine and catalytic converter damage.



BTW, I had the slow return to idle symtoms, high idle, and the hesitation on full throttle. My rpm's would dip by about 200rpm when I hit the throttle, then go.

ontarff
11-17-13, 02:19 PM
I can't get to the Phillip's head retaining screws for the TPS on my 2001 ETC.

stoveguyy
11-19-13, 10:31 AM
http://img.photobucket.com/albums/v496/joemn/P1080357_zps5b53a7dc.jpg (http://smg.photobucket.com/user/joemn/media/P1080357_zps5b53a7dc.jpg.html)you need to remove dogbone mount
Mine are Torx head also