Scary cruise control issue

Jackstevens98 · 12th February 2018, 19:31

I was driving this evening and used cruise control as I was on a long steady road at 50mph had no issues and after a while I had to brake which disengages the cruise control. About 15 minutes later I put it back on at 30mph the car instantly accelerated but went past 30mph so I clicked off the cruise control button on the steering wheel. I tried it again some minutes later and the same issue so I switched it off again but the engine kept on revving. Luckily it wasn’t busy I had to brake hard while the engine was still revving by itself and had to pull over and go straight into park and handbrake on while the car was still moving. I switched the engine off and left for a few minutes and started the car again and it revved very hard again so I killed the engine again. I then turned the key to the second key control and pressed the cruise control button on the dash several times on and off. Then started the engine and all okay so I could travel home. Just not sure what could have caused this and don’t want to use the cruise again just in case any ideas? If it makes an difference I’m running a 99 75 2.5 v6 auto

bendrick · 12th February 2018, 19:57

I seem to recall there was an incident with another member before Christmas , when a simliar thing happened approaching a road accident and he sped through a police road block almost hitting a policeman before regaining control.

JSS · 13th February 2018, 00:23

Same thing happened to me. First lost of cruise control and 10 minutes later, car started accelerate by itself. Breaking hard and switched engine off.
Haven't used CC since. I will take car to the service to see, if T4 will find anything.

Couple of days before I did have ABS problem and it was related Navall 3 wiring, but not sure did this have anything to do with cruise problem.

alanaslan · 13th February 2018, 01:53

Quote:

Originally Posted by Jackstevens98

I was driving this evening and used cruise control as I was on a long steady road at 50mph had no issues and after a while I had to brake which disengages the cruise control. About 15 minutes later I put it back on at 30mph the car instantly accelerated but went past 30mph so I clicked off the cruise control button on the steering wheel. I tried it again some minutes later and the same issue so I switched it off again but the engine kept on revving. Luckily it wasn’t busy I had to brake hard while the engine was still revving by itself and had to pull over and go straight into park and handbrake on while the car was still moving. I switched the engine off and left for a few minutes and started the car again and it revved very hard again so I killed the engine again. I then turned the key to the second key control and pressed the cruise control button on the dash several times on and off. Then started the engine and all okay so I could travel home. Just not sure what could have caused this and don’t want to use the cruise again just in case any ideas? If it makes an difference I’m running a 99 75 2.5 v6 auto

I am afraid I have no answers, both my current road cars are Cdti autos, the tourer has once tried running away. But I just ignition off and back on and it cleared it. That evening it spent an hour or so on the computer but the car had no recollection of having. Had done it and the system checked I know that the system uses vacuum pressure in its calculation and in the diesel there is very little change in the vacuum from full throttle to over run. So it must be a very tight algorithm. So for me it was an oil change air filter wash and re oil oil and crankcase filter change and a top up with Mobile 1 Diesel with a can of slick fifty to smother things over.
Since that day to this never had the problem again. All filters are changed twice as often as recommended and they both get high quality fully synthetic with a can of slick every fourth change. I personally think that this is just down to old age.
Sorry this is of little help but you are not alone.

Gate Keeper · 13th February 2018, 04:13

Quote:

Originally Posted by bendrick

I seem to recall there was an incident with another member before Christmas , when a simliar thing happened approaching a road accident and he sped through a police road block almost hitting a policeman before regaining control.

The brakes failed at 60 mph with CC activated. It happened in October going into London on the A40, I was a front seat passenger. We clipped the back of a Royal Mail truck going through the road block. The driver, was banned member Rover54. Ed skillfully got us through the smashed up cars at the scene of an RTA and the car, a Rover 75 Tourer, stopped 1-2 miles down the road.

Recently Ed was informed by the police that all charges have been dropped. They tried to put it down to reckless driving, when it was really due to a mechanical fault.

hrissim · 13th February 2018, 04:16

Check carefully along all the way CC catch/cable in the engine bay especially the part near manifold to the throttle body. Check there is attached to the throttle body part - move that part down-up. Lubricate with some thin oil.
Seems to be a mechanical issue.

Gate Keeper · 13th February 2018, 04:38

There was a thread called “Rover54”, posted up following the incident. Shiner carried out repairs to a split hose, as being the source of the failure

Quote:

Originally Posted by shiner

This also happened to our 75 cdt auto. Didn't get up to any speed with the issue as happened manoeuvring, the brake pedal was solid like there was no servo assistance at all. Turn off and back on assistance returned then gone again. Also was a split hose between the egr solinoid and the vacuum pipe from the servo.

Sent from my F5121 using Tapatalk

Quote:

Originally Posted by hrissim

Check carefully along all the way CC catch/cable in the engine bay especially the part near manifold to the throttle body. Check there is attached to the throttle body part - move that part down-up. Lubricate with some thin oil.
Seems to be a mechanical issue.

Mike Noc · 13th February 2018, 07:48

Quote:

Originally Posted by alanaslan

I am afraid I have no answers, both my current road cars are Cdti autos, the tourer has once tried running away. But I just ignition off and back on and it cleared it. That evening it spent an hour or so on the computer but the car had no recollection of having. Had done it and the system checked I know that the system uses vacuum pressure in its calculation and in the diesel there is very little change in the vacuum from full throttle to over run. So it must be a very tight algorithm.

Completely different system for cruise on the diesels compared to the V6 though Alan.

The diesel is drive by wire, and the V6 mechanical, so maybe the OP has a problem with linkages?

Are you saying the diesel uses vacuum in the calculation? Strange because there isn't a vacuum in the inlet manifold, which is why they fitted a vacuum pump on the end of the exhaust camshaft.

ChestersDad · 13th February 2018, 09:12

Hi there - knew I had read about this some time before a few years back:
Hope I am on the right track and this helps:

Courtesy of Rob's excellent post (I hope you still have that gorgeous one off Tourer of yours Rob!

championdaddy · 13th February 2018, 18:39

I had the same with mine......but only on the auto.......

If you resumed the speed after slowing........it would rev the bejesus out of the engine to get back up to speed as fast as possible.

Once back to the set speed.....it was perfect again.

But as I said......Only on the auto where it could change the gears itself.

12th February 2018, 19:31	#1
Jackstevens98 Loves to post Rover 75 Join Date: May 2017 Location: Sussex Posts: 354 Thanks: 41 Thanked 50 Times in 35 Posts	Scary cruise control issue I was driving this evening and used cruise control as I was on a long steady road at 50mph had no issues and after a while I had to brake which disengages the cruise control. About 15 minutes later I put it back on at 30mph the car instantly accelerated but went past 30mph so I clicked off the cruise control button on the steering wheel. I tried it again some minutes later and the same issue so I switched it off again but the engine kept on revving. Luckily it wasn’t busy I had to brake hard while the engine was still revving by itself and had to pull over and go straight into park and handbrake on while the car was still moving. I switched the engine off and left for a few minutes and started the car again and it revved very hard again so I killed the engine again. I then turned the key to the second key control and pressed the cruise control button on the dash several times on and off. Then started the engine and all okay so I could travel home. Just not sure what could have caused this and don’t want to use the cruise again just in case any ideas? If it makes an difference I’m running a 99 75 2.5 v6 auto

13th February 2018, 04:16	#6
hrissim Gets stuck in 75 MK1 2.5 V6 Saloon Join Date: May 2017 Location: Samokov Posts: 781 Thanks: 372 Thanked 423 Times in 240 Posts	Check carefully along all the way CC catch/cable in the engine bay especially the part near manifold to the throttle body. Check there is attached to the throttle body part - move that part down-up. Lubricate with some thin oil. Seems to be a mechanical issue. __________________ Don`t drive faster than your guardian-angel can fly!

13th February 2018, 09:12	#9
ChestersDad Still 75less :-( 1988 Defender 90 Join Date: Jun 2011 Location: Carmarthenshire Posts: 531 Thanks: 15 Thanked 93 Times in 37 Posts	Hi there - knew I had read about this some time before a few years back: Hope I am on the right track and this helps: Courtesy of Rob's excellent post (I hope you still have that gorgeous one off Tourer of yours Rob! __________________ Don't save for the future as someone else will lose it for you!

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12th February 2018, 19:57	#2
bendrick Gets stuck in Ex CDT Auto Join Date: Oct 2017 Location: Barry Posts: 655 Thanks: 76 Thanked 266 Times in 155 Posts	I seem to recall there was an incident with another member before Christmas , when a simliar thing happened approaching a road accident and he sped through a police road block almost hitting a policeman before regaining control.

13th February 2018, 00:23	#3
JSS Avid contributor Rover 75 Connoisseur 1999 LHD Dealer launch car 100532 Join Date: Jan 2008 Location: FINLAND Posts: 112 Thanks: 27 Thanked 14 Times in 8 Posts	Same thing happened to me. First lost of cruise control and 10 minutes later, car started accelerate by itself. Breaking hard and switched engine off. Haven't used CC since. I will take car to the service to see, if T4 will find anything. Couple of days before I did have ABS problem and it was related Navall 3 wiring, but not sure did this have anything to do with cruise problem.

13th February 2018, 18:39	#10
championdaddy This is my second home Mg Zt 190 Join Date: Apr 2012 Location: The FIRST Garden City....Letchworth. Posts: 6,778 Thanks: 1,243 Thanked 920 Times in 698 Posts	I had the same with mine......but only on the auto....... If you resumed the speed after slowing........it would rev the bejesus out of the engine to get back up to speed as fast as possible. Once back to the set speed.....it was perfect again. But as I said......Only on the auto where it could change the gears itself.