[thewizardofodds]

Mates 2000 scenic has a misfire, car shakes on idle and apparently looses power going up hills etcSomeone said it was burnt valve but dont know why as they havent looked at it.
Anyway I gad quick look at it and if I disconnect ANY of the coils the engine cuts out cmpletely straight away.
Any ideas?

 

[jubb]

Probably because its only running on 3 to start with. If this is a 2litre petrol it may well be a burnt exhaust valve, not uncommon on these engines

 

[thewizardofodds]

Probably because its only running on 3 to start with. If this is a 2litre petrol it may well be a burnt exhaust valve, not uncommon on these engines

Thats what I was thinking . but surely if I unplugged the one that wasnt running there would be no difference?
Its a 1.6 engine.

 

[madnoel10]

Disconnecting spark plugs isn't always a good test. Disconnecting each injector in turn is a better method.

If it is a burnt valve then a simple dry and wet compression test would reveal more.

 

[jubb]

Thats what I was thinking . but surely if I unplugged the one that wasnt running there would be no difference?
Its a 1.6 engine.

I take it there are four individual coils then. On mine i had 2double coils so disconecting one coil stopped 2 cylinders.

 

[thewizardofodds]

its out the back now so will go and try injectors now. Was going to do a compression test but dont have a tester and eurocarparts didnt have any in stock.

 

[thewizardofodds]

Ok just tried the injectors if i disconnect 1 or 3 (going left to right) nothing happens but if i disconnect 2 or 4 it cuts out straight away

 

[madnoel10]

Renault cylinders are always numbered from the flywheel end of the engine

If you disconnect an injector and there is no effect then the engine isn't firing on that cylinder. So it would appear cylinders number 2 and 4 ain't working.

Have you checked these cylinders are getting a spark or have you removed the spark plugs for inspection??

 

[thewizardofodds]

Renault cylinders are always numbered from the flywheel end of the engine

If you disconnect an injector and there is no effect then the engine isn't firing on that cylinder. So it would appear cylinders number 2 and 4 ain't working.

Have you checked these cylinders are getting a spark or have you removed the spark plugs for inspection??

changed plugs today as all 4 were burnt ie melted , not the electrode but the earth bit.
check the injectors with ohm meter and all same reading

 

[madnoel10]

It is very rare to come across melted plug tips.

Sounds like either the incorrect plugs are being used or the engine is running very lean. A leak in the inlet manifold would cause this problem and also poor ignition.

 

[thewizardofodds]

It is very rare to come across melted plug tips.

Sounds like either the incorrect plugs are being used or the engine is running very lean. A leak in the inlet manifold would cause this problem and also poor ignition.

re the plugs. I had a set of plugs from a 1.1. saxo that I hadnt fitted in the garage. Now according to eurocarparts these plugs are the same for a scenic 1.6 which I thought was a bit odd.

 

[thewizardofodds]

did compression test and cylinder 2 is 1psi so looking like burnt valve after all ;-(