2003 LeSabre 3.8 engine races at start up, idles at 1500, and accelerates on its own.

[DesireeR]

I pulled off the Throttle body first to clean and inspect it. Upon removal it was apparent that there was serious gum-up in the upper and lower intake manifold. Removed, cleaned and reinstalled the upper and lower intake manifold and the Throttle body. Issue persisted with no change. Replaced the Throttle Position Sensor (TPS) No change. Replaced Idle Air Control Valve Sensor (IAC). At first change the car still raced at startup and idled high. Let it run for about 3 minutes to see if it would self calibrate. no change. took it for a drive around the neighborhood and the idle dropped to 800 when my foot was not on the gas pedal and it did not accelerate on its own. When I arrived at my location I turned off the car. Upon startup the engine raced again and idled high at 1500 and did not fix itself. It still races at start-up, idles at 1500, and accelerates on his own. Every once in a while it will work, but it is completely random... I plan on checking for an air leak anywhere in the intake lines and connections... I'm getting pretty frustrated. Any other ideas? maybe someone on Oahu in HI that's willing to come take a look?

 

[DonP]

Re: 2003 LeSabre 3.8 engine races at start up, idles at 1500, and accelerates on its

Any codes, including hidden codes.
Ar the gauge indications and operating parameters (e.g., coolant temp) normal?
If it clears occasionally it sounds like an intermittent.
Can you put a recording scanner on it and monitor the various parameters.

 

[DesireeR]

First of all, what is a hidden code?

The engine service light finally lit and it threw a code the other day. "P0122 Throttle/Pedal Position Sensor A Circuit Low Input" I did not clear it to see if it would clear itself; and after driving it up the hill and back it had cleared. The fault is much more continuous as well. It races up to 2800 upon startup, almost every time, even after all the replaced parts, and the appears not to be any vacuum leaks either.

The coolant temp also fluctuates. I did replace the thermostat.

I do not have a "recording scanner"

 

[DonP]

Re: 2003 LeSabre 3.8 engine races at start up, idles at 1500, and accelerates on its

P0122 - This DTC detects a continuous short to low or open in either the signal circuit or the TP sensor.

Hidden Codes are codes that do not set the malfunction/service engine sool light. However, they are stored by the system for diagnostic purposes. Some may self-clear if the issue is resolved.

Given that both the TPS and t-stat were worked on/replaced, it sounds like there maybe a bad or intermitent ground or connection in the system.

 

[HotZ28]

When you installed the new TPS, did you place the drive tab of the sensor behind the actuator pin in the throttle body, as described in the video below?

https://www.youtube.com/watch?v=UQRZwRxiK1A

 

[mrmajikbus45]

Re: 2003 LeSabre 3.8 engine races at start up, idles at 1500, and accelerates on its

HotZ28 is right, I did that once and had very similar issues.