Engine speed increases on its own

Chimfender · 2nd May 2024, 18:21

I have a an 02 KV6 Conny SE Auto Saloon.
Always runs fine except yesterday. Stopped at the traffic lights with lever in D engine ticking over at normal idle speed foot on brake. Suddenly the engine speed slowly increases to around 2000 rpm then comes back to idle. I resisted the car moving by increasing the foot brake pressure. It then happens again 2 or three times. I then notice rhat when it happens, curiously the water temp gauge needle falls back to zero then goes back up to normal when the revs drop. Driving away when the lights change the engine appears to be ok and the fault appears to have cleared. My first thought without to much knowledge was throttle pot but how would the water temp gauge movement be related it seems crazy. Any ideas would be appreciated

Popcorn · 3rd May 2024, 02:04

It may be the temperature sender unit faulty,when it goes to zero the ECU thinks the engine is cold and goes into fast idle, but more knowledgeable people will be able to pinpoint it for you

Chimfender · 3rd May 2024, 14:51

Thanks Sean, it sounds very plausible. Away tomorrow for a while but will order a new sensor from DMGRS when I get back. Thank you for responding.

2nd May 2024, 18:21	#1
Chimfender Chimfender Rover 75 Saloon Join Date: Apr 2023 Location: Swindon Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Engine speed increases on its own I have a an 02 KV6 Conny SE Auto Saloon. Always runs fine except yesterday. Stopped at the traffic lights with lever in D engine ticking over at normal idle speed foot on brake. Suddenly the engine speed slowly increases to around 2000 rpm then comes back to idle. I resisted the car moving by increasing the foot brake pressure. It then happens again 2 or three times. I then notice rhat when it happens, curiously the water temp gauge needle falls back to zero then goes back up to normal when the revs drop. Driving away when the lights change the engine appears to be ok and the fault appears to have cleared. My first thought without to much knowledge was throttle pot but how would the water temp gauge movement be related it seems crazy. Any ideas would be appreciated

3rd May 2024, 02:04	#2
Popcorn Loves to post 55 cdti tourer slush box executive grill Join Date: Feb 2022 Location: Sheffield Posts: 391 Thanks: 40 Thanked 85 Times in 72 Posts	It may be the temperature sender unit faulty,when it goes to zero the ECU thinks the engine is cold and goes into fast idle, but more knowledgeable people will be able to pinpoint it for you

3rd May 2024, 14:51	#3
Chimfender Chimfender Rover 75 Saloon Join Date: Apr 2023 Location: Swindon Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks Sean, it sounds very plausible. Away tomorrow for a while but will order a new sensor from DMGRS when I get back. Thank you for responding.