misfire

[combatjohnny]

slight misfire 3.5 efi had this problem for a while now running out of idea's
changed rotor arm,leads dizzy cap plugs had a compression test everything ok. any ideas would be gratefull

[Range Rover Blues]

Leak in the inlet manifold
weak valve spring
wear in the rotor shaft of the dizzy
worn cam
dodgy coil
ooh, f**ked injector, over/under fueling

[combatjohnny]

Thanks alot thought I had narrowed things down and you throw more questions in my head and spanners in the works so to speak.
Hoping it wasn't anything like inlet,  just wishful thinking I thought.
Still if needs be suppose I'll have to try it if not to cross off the list.
Not a hard job but finding the time is.
Thankyou anyway for confirming  my fears.

[Range Rover Blues]

Well if your comprssion is ok then the engine is sound, an inlet leak would be more noticeable at or just above idle rather than at full chat.

Valve problems/cam problems, any noise at the top end?
Injector, any of the plugs a bit black?  is it a tas thirsty?

Ignition, try getting hold of a spark tester, its a pair of callipers that you connect in series with the coil/dizzy and watch the sparks as it were.. You can test spark stregth but also watch for irregularities in the spark pattern.

Try checking the timing, any timing bounce (variation) and the dizzy is worn.  Check it at speed too and don't forget the vacuum.

[combatjohnny]

Sorted finially with your help. Thankyou done the inlet gasket anyway
but the problem was an injector swap it with another and problem followed
so I'll get hold of one tomorrow. Job done cheers mate.