2.5 KV6 auto missfire / imbalance?

[M47Rman]

Hi all
just noticed this today on our 2.5 v6 auto. With the car in neutral or park, if I raise the revs from idle, inbetween about 800 and 1000 rpm, there is a vibration, which can be felt through the steering wheel, floor, gearlever, in fact most of the car. Above and below this speed band, the vibration vanishes. I can not pin the speed down any more accurately, as it is very difficult to maintain a constant engine speed in that area. Has anyone come across this before? Do all KV6 do it? If so is it a missfire, cylinder imbalance or what?
Anyone got any ideas?
Andy

[GreyGhost]

What's the age and mileage. May help with diagnosis. It is not a normal occurrence.

[M47Rman]

What's the age and mileage. May help with diagnosis. It is not a normal occurrence.

The car is a 2001 model, and has completed 60000 miles.

[Mike]

Mt first thought is the flexi pipe coupling between the exhaust manifold down pipe and exhaust - it can be very noisy when it fails.

hth

Mike

[Mike]

ps can I just ask? :) you have a KV6 and yet your name is M47R (ie the 75 Diesel) Can I ask why?

Regards

Mike

[M47Rman]

Hi Mike
I will check the flex pipe, but I do not think that is the problem. It feels more like a slight missfire from the engine. Not sure I would even have found it if I had not got stuck in a traffic jam!
As for M47R v KV6, I worked in Rover Group diesel development from 1994 to 2001, having been an apprentice for the previous 4 years, and I worked on M47R (amongst other things) for Rover 75 and Freelander. However, when it came to buying a car, my wife preferred the sound and performance of the V6 petrol - and who am I to argue. Equally though, I wanted a proper British car, so it had to have a proper British engine, rather than a British development of an austrian engine!
Andy

[Mike]

Thanks for letting us know the story :)

I haven't heard many reports about misfires on the KV6 and faulty coil packs are a likely culprit, together with the front bank HT leads.

It'll be good for Lates to have a look at this thread for you. In the meantime I'll see what else I might find.

Mike

[Mike]

Another thought is one or both of your vis valve motors could be playing up. Two motorised valves on the inlet manifold, the motors can play up and thus really mess up engine behaviour and cause rough running. Does the car misbehave when driving- i.e. rough gear changes, lack of the little oomph and push in the back at 3200 rpm?

A Testbook or engine diagnostic would tell you a lot more. Peterborough isn't that far from the M45/A45 - I say contact Lates if you can or get the diagnostics done by a dealer Marshalls are near to you aren't they?

Mike

[M47Rman]

Another thought is one or both of your vis valve motors could be playing up. Two motorised valves on the inlet manifold, the motors can play up and thus really mess up engine behaviour and cause rough running. Does the car misbehave when driving- i.e. rough gear changes, lack of the little oomph and push in the back at 3200 rpm?

A Testbook or engine diagnostic would tell you a lot more. Peterborough isn't that far from the M45/A45 - I say contact Lates if you can or get the diagnostics done by a dealer Marshalls are near to you aren't they?

Mike

The car drives very well, and although I have limited experience of KV6 performance, I would say the performance is more than adequate! The only change that is less than totally smooth is the first to second upshift, and even that is not bad. As for vis valves, I know that the car had a new inlet manifold, fitted by a Rover dealer about 10000 miles ago. Not sure if this would have entailed new vis valves or not. The car was at Brands, an independant (ex) Rover dealer near Spalding just over a week ago, where we had the timing belts and ancillary belts changed, and also a new key programmed. They had the car on testbook to do the key, and also to reset the service indicator. I assume any problems of an electronic nature would have been flagged up automatically?? The car may well be going back soon anyway, as since the belts were changed, we have smelt coolant after driving. No sign of any leaks, although it would appear to have been slightly overfilled, as the coolant level is above the max mark.
Sorry to sound thick, but who or what is Lates
Thanks for your help
Andy

[M47Rman]

Oh by the way Mike
you are right that Marshalls are near us, but having had EXPERIENCE of them in the past, I would only use them again if they were the last dealer on the planet!
Andy

[GreyGhost]

http://www.lates600.com/

Lates logs on here to help us all out as well as providing the services on shown on his web site. Highly recommended.

PM or Email him if you need hands on assistance from an expert.

[Mike]

Lates is a member on here and an acknowledged expert tech on the 75/ZT. He has serviced many members cars inc. my own (cambelt change) and is highly regarded.

More info here

http://www.the75andztclub.co.uk/forum/member.php?u=62

hth

Mike

[Mike]

Oh by the way Mike
you are right that Marshalls are near us, but having had EXPERIENCE of them in the past, I would only use them again if they were the last dealer on the planet!
Andy

:rofl: point taken Andy ;) Even more reason to speak to Lates :)

[M47Rman]

Thanks for the info on lates both. At least there is someone reliable to turn to if need be.
Andy

[Lates]

Apologies for jumping on this thread "late" as some of you know I have been on a funny shift.

It does sound a little odd to be honest having any imbalance/vibration through the car. I would also be a little cynical and ask if it was there before the belts were changed ;)

I have no worries if you wish to bring it up for us to look at, but in hindsight I would also be chancing my arm at the dealer to put it back on T4 or to recheck the fixings on the belt job :)

Hope this helps
Lates

[M47Rman]

Apologies for jumping on this thread "late" as some of you know I have been on a funny shift.

It does sound a little odd to be honest having any imbalance/vibration through the car. I would also be a little cynical and ask if it was there before the belts were changed ;)

I have no worries if you wish to bring it up for us to look at, but in hindsight I would also be chancing my arm at the dealer to put it back on T4 or to recheck the fixings on the belt job :)

Hope this helps
Lates

Thanks Lates - the car is going back in on Saturday for the dealer to have a look see!
Andy

[M47Rman]

Latest report on the KV6 missfire/imbalance. We took the car back to the local Rover dealer on Saturday for a look see. They agreed that there was a vibration between 800 to 1000 rpm. They checked the car out on testbook, and all appeared fine. They checked the plenum drains (and cleaned them out) and there was no sign of any ECU drowning! As a final thought, they loosened off the engine mounting fixings, and retorqued - and hey presto the problem has gone! There is now the slightest vibration at this speed, far better than just after the belt change. Interestingly though, the dealer told us that the KV6 is not totally smooth at this sort of speed, and that some vibration is common.
They also checked the cooling system, as we had been smelling coolant since the belt change, and it would appear this was down to a slight overfill of the system. The excess it would appear has been vented, as we are no longer geting the smell, and the level is stable at the max point.
Thanks to all who offered their thoughts
Andy:D

[Mike]

Great news Andy :D Glad it's all sorted for you.

Regards

Mike

[Lates]

Happy days Andy, good to hear the dealer sorted you out :)

[MikeHurley]

I think I have exactly the same vibe as in the 1st post above. So may do exactly the same by having the new mount fixing loosened and retorqued. Otherwise, the process of elimination, unbalanced cylinders, tie rods, drop links or anti roll ar bushes. :(

Sorry to continue on such an old post ;)