TPS replacement - High idle

roverzfan

Member
Nov 7, 2006
18
0
Florida
Wondering if anyone can provide some insight. I have a 98 Disco. The TPS sensor was testing bad With the multi-meter so I ordered a new OEM replacement. I’m not a mechanic but I’m pretty good at replacing parts. TPS looks pretty simple. Unplug electrical connector, remove 2 screws, pull old sensor, replace in reverse. However the new sensor has the car idling at about 1800 RPMs. Am I missing a step? It fit just fine and looking at the two sensors the little plastic pieces that allow the sensor to move based on the throttle shaft seem to be in the same alignment so that doesn’t seem to be the issue. As far as I can tell there is no idle adjustments. Any help would be appreciated.
 

discostew

Well-known member
Sep 14, 2010
5,849
316
Northern Illinois
Tell me how it tested bad with a multi meter. But If it was a bad sensor and you replaced it, thats a part that needs to have closed throttle position and adaptions relearned. Closed throttle position is pretty important. If the ECM thinks your tipping into the throttle it dumps fuel because it's anticipating a load is about to come.
 

roverzfan

Member
Nov 7, 2006
18
0
Florida
Thanks for the response. The rover would accelerate and then have a spot where it wouldn’t go faster and then if I mashed the gas it would go accelerate again. Testing with the multi-meter showed it had voltage drops vs staying linear through the throttle range. How do you retrain the ECM for closed throttle?
 

robertf

Well-known member
Jan 22, 2006
4,206
81
-
Need a scan tool to “retrain” aka reset adaptive values

see here for one

 

roverzfan

Member
Nov 7, 2006
18
0
Florida
So I wasn’t aware I’d need a scan tool to do a retrain. I’ll check out RobertF’s suggestion.

Discostew - as far as sweeping the new one it sweeps fine but when releasing (aka no throttle) it still has the high idle. So does that confirm the retrain idea?
 

discostew

Well-known member
Sep 14, 2010
5,849
316
Northern Illinois
You said you checked it with a multi meter and it was bad. If it was one voltage drop at about center travel and then went back to a good linear pattern it might have been normal. robertf could probably explain it a lot better than me. What I know from experience is that early throttle position sensorss did this.

Yes you will need a scan tool to reset your adaptions. I always reset closed throttle position also because I've had problems just resetting adaptions. But I used to use something called T4. But that shit the bed like every other one around here. Now I'm in the same boat you are.
 

roverzfan

Member
Nov 7, 2006
18
0
Florida
Thanks for the guidance everyone. I‘ll get the scan tool situation figured out and then report back. Thankfully this isn’t my daily driver.
 

robertf

Well-known member
Jan 22, 2006
4,206
81
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I can confirm its false. The GEMS ecu doesnt have a constant power source, only a latching relay that disconnects from the battery a few seconds after the vehicle is off and there is no active obd2 communications