Low Rev Vibration

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btbc192

New Member
Posts
12
Location
Askern Doncaster
Hi All, Is there a 3.5 specialist in the house. I have an 88 petrol Range Rover that has suddenly developed a vibration at low revs. It starts OK and once over about 1000 revs seems to run perfectly. If the engine is cold then the it feels as if there is nothing wrong. As the motor warms up in comes the vibration. I have tried all of the plug leads and the plugs. I found that the No 2 plug on the near side was nearly white and there was a slight oil deposit around the thread of No 3 plug on the off side. By lifting off the plug lead on each cylinder in turn had the same effect on all cylinders
Any ideas please, the motor has never missed a beat before or given any indication of a vibration.
Many thanks Ian
 
btbc192 said:
Hi All, Is there a 3.5 specialist in the house. I have an 88 petrol Range Rover that has suddenly developed a vibration at low revs. It starts OK and once over about 1000 revs seems to run perfectly. If the engine is cold then the it feels as if there is nothing wrong. As the motor warms up in comes the vibration. I have tried all of the plug leads and the plugs. I found that the No 2 plug on the near side was nearly white and there was a slight oil deposit around the thread of No 3 plug on the off side. By lifting off the plug lead on each cylinder in turn had the same effect on all cylinders
Any ideas please, the motor has never missed a beat before or given any indication of a vibration.
Many thanks Ian
Click to expand...

When you say No 2 plug was nearly white, do you mean clean? If that is the case it is a sure sign of water getting into the cylinder i am afraid.
 
is it automatic by any chance,?
and where abouts are you, if you add your location to your profile it help as there may be one us of near you.
 
Last edited:
Hi, Wammers and 1992 lse, Thankyou for your replies, I had not even considered water ingress, but now you mention it the water level was a bit low, the spark plug was very clean, no evidence of any colour of carbon build up. I have heard of V8 blocks going porous but never considered it. Yes it is an automatic, and my location is North Doncaster, and I will amend my profile.
 
btbc192 said:
Hi, Wammers and 1992 lse, Thankyou for your replies, I had not even considered water ingress, but now you mention it the water level was a bit low, the spark plug was very clean, no evidence of any colour of carbon build up. I have heard of V8 blocks going porous but never considered it. Yes it is an automatic, and my location is North Doncaster, and I will amend my profile.
Click to expand...

Forget the porous block it is a myth. If the plug was clean then it is certainly due to water ingress. The plug is being steam cleaned as combustion takes place. Most likely head gasket gone between that cylinder and water jacket. Or a crack in inlet side of head. Only place water can get into combustion chamber from block is joint between block and liner. Hence when that happens, porous block syndrom.
 
Hi Wammers, what you are saying is making a lot of sense, I will procede in that direction. In the back of my mind I knew that it was going to be a strip down it, as my only other thought was that I had nipped a valve and bent it. I will gather my tools and let you know the outcome.
Thank you very much for your help,
Regards Ian
 
btbc192 said:
Hi Wammers, what you are saying is making a lot of sense, I will procede in that direction. In the back of my mind I knew that it was going to be a strip down it, as my only other thought was that I had nipped a valve and bent it. I will gather my tools and let you know the outcome.
Thank you very much for your help,
Regards Ian
Click to expand...

You will need to have a look, but if water was passing the gasket you would expect combustion gases to be forced back the other way pressurising system. So it may not be as straight forward as it may seem. I think you said it was ok cold but showed the symptoms when hot this would seem to indicate something opening up as engine warms.
 
Hi Wammers, Sorry I did not get back sooner. Gave the motor a run around the local roads and could not detect any adverse pressure in the cooloing system. The water is going somewhere as the level was below where I had topped up to. I am going to have to put things down for the weekend due to other commitments. I will get back on it on Monday and let you know any changes.
Thanks again for your help, brilliant.
Regards Ian
 
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