S4 misfire

[RonnieS]

Hi,

Having trouble solving a misfire on an S4 Elan.

Misfire starts after about 7 or 8 miles.
Seems independent of water temperature.
Have replaced all ignition components.
Have replaced fuel pump and readjusted carbs.
Have checked and fixed brake servo/manifold.
Have taken cam cover off and found one tight tappet, would that be enough to cause the problem? (Haven't had a chance to run car yet.)

Any suggestions??

Ronnie

[john.p.clegg]

I suppose if you have a tight tappet,as the engine warms up the clearance wil lessen-could very well be your problem
John

[types26/36]

I'm of the opposite opinion to John, unless the tappet had zero clearence (riding the valve) I doubt it would cause the misfire.
Brian.

[types26/36]

Ronnie,
Although you have replaced the ign components does that include H.T. cables, plug connectors (suppressors) dist. cap and rotor ? if not check for a high resistance in these components, also check for corrosion in the coil tower.
Brian

[RonnieS]

Fixing tight tappet hasn't solved problem... more hair coming out

RonnieS

[nebogipfel]

Just a thought, Is the fuel tank venting OK? If it happens always after a few miles fuel starvation has to be a possibility.

The other thought is that although you say it doesn't seem to be water temp' related, after a few miles things are warming up. In the good old days coil and condenser breakdown was often heat related. If you have electronic ignition fitted the same could certainly apply to that.

[tonycharente]

If the car is on Strombergs, have you checked that the valves in the temperature compensators are not stuck closed?