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porscheguru
porscheguru, Technician
Category: Car
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Experience:  Highline automotive technician
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rover sd1 vitesse: My car is a twin plenum 1986 Rover sd1 Vitesse

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My car is a twin plenum 1986 Rover sd1 Vitesse 5speed. It has a fine engine vibration I cannot diagnose. I have ruled out the entire drive-chain - depression of clutch etc makes no difference. Vibration is present at all revs and while standing still.
Always apparent through steering wheel and gear leaver.
I suspect either flywheel, clutch pressure plate, alternator/generator, or an exhaust valve not closing properly. (Very slight fuffing from the exhaust - only just detectable. Engine runs sweet but blows the blues on start up for a minute or so. I intend to remove the belts and disable alt / generator first to see if that fixes it - I suspect it won't. Where to from there please?.

porscheguru : Good morning, Are you still standing by?
porscheguru : I just realized you are from New Zealand so good morning is not correct!
Customer:

standing by!

porscheguru : I think you're correct in your diagnosis procedure. Removing the belts (although not an easy task) first is what you have to do. I have a customer that has a variation on one of these. Pretty cool car! Didn't! These have viscous coupling issues?
porscheguru : By stating "blows the blues" upon startup may I ask have you checked the spark plugs and analyzed them?
Customer:

Spark plugs look good once the engine is hot - havn't checked them after a cold start. Wondering about doing a compression test - what figure should their compressions be around? 145 psi??? I don't think it's a high compression 3.5 but it could be - I dont know exactly what changes Lotus did to the twin plenum - this one was the last sd1 ever made. Yes Viscous coupling is an issue, although I don't know how one can tell when there's trouble brewing. I guess, in asking you, I"m trying to tap into your experience of a high frequency vibration in pushrod v8's - something a lot of mechanics don't have much experience of.

porscheguru : Right and Porsche was not a pushrod type of mfgr! But I had a 944 with a very weird vibration and it wound up being a ever so slightly bent connecting rod on cyll # XXXXX Seems the injector cause a slight hydro lock and bent that rod and it was a bear to diagnose. I am sure you have searched for the issue wi the VC but here is a link. http://www.roversd1.nl/sd1web/viscofan.html
porscheguru : Hang a sec please ok?
porscheguru : I am still here but a. Opulent more secs
porscheguru : Couple more secs
Customer:

Yeah I wondered if it might be something like that - what about a tooth or two off the flywheel - would that account for it or doesn't that sort of thing happen much? How does one diagnose an out of balance crankshaft, conrod or flywheel I wonder?

porscheguru : That is difficult BUT if you have any stick on wheel weight you can strategically place one, maybe 5 grams and start the car. And see what happens. Duct tape it on to the vibration damper. If worse, then place it 90 degrees in another direction. Et etc. I would scrutinize the plugs, and perform a compression test. The Exact value is not as important as making sure the values are similar for all cylinders. If you are able to start the car without the crank pulley for a short time, this could help. I had a car ( pre dual mass flywheel) that had a bad crank pulley aka vibration damper. I caused a vibration similar to yours and intermittently caused a irritating squeak.
Customer:

Are you thinking that it could be the crank pulley or vibration damper it'self that might be at fault, or just using them to locate a crankshaft problem?

porscheguru : So for a procedure to start, remove the belts and see if the VC is causing the vibration. It is the easiest. Then analyze the plugs again and make sure the vibration is not being caused by an internal problem or possibly a cylinder that is not in tune. But while the belts are off, and if possible, run the car without the front pulley. I am not sure if thIs is possible but evaluate the arrangement and if so, try it. It is called the vibration dampner for a reason. I just saw your reply. I am hoping for your sake it is the pulley. It could be something like a cylinder has a buch of carbon on top of the cylinder causing it to be out of balance.
porscheguru : Bunch of carbon. Typo
porscheguru : Why don,t you try those easy things and get back to me. I don't have any friends in New Zealand! :-)
Customer:

OK, thanks for that - I'll try it. One final question - On the start-up oil burn, how do I tell whether it's coming in via the exhaust or inlet valve guides?


PS I'm a psychotherapist who collects British Leyland cars for a hobby - got 5 SD1's of various kinds, Daimler x300, 2x Austin Princess 1800 and Rover P6B-S - all beautiful, all leak oil - all break my heart regularly - just like my woman. - c'est la vie!

porscheguru : If either one is bad, the engine has to be torn apart to fix and once you are there you are going to replace both intake and exhaust valves. So I would not worry about that. We have late model Porsches that produce embarrassing smoke on startup and it is considered normal. Hey, I gotta get going to that regular job I have but I have a PC right at my tool box and I have an alert on my phone as soon as you want me to reply. I am available at all times but we are like 12 hours flip flopped on our schedule. Regardless, I think you have a real good grasp on this to start and I want to be available for you. S check the VC and get back to me as soon as that is eliminated ok?
Customer:

OK thanks a heap. Talk later.

porscheguru : Take car my friend and tell me the findings of the VC and I will ask around in my network for your situation. Bye!
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