Car occasionaly misfires

[phunk]

Ever since I have had my Elan, it's always taken a little while to start, always first time, but it takes a while.

Occasionally when driving with a wide open throttle it misfires a tad.

My local garage thinks that it could be the coil packs?

The car is a S2 with a 2.25 Piper and Everest chip.

Any ideas?

[madbilly]

I had a problem very recently that sound similar. I think I cured it by fixing the peg/dowel in the CAS drive off the exhaust camshaft. If the peg isn't in place correctly the CAS disc will have play in it - 8 degrees on mine - which can lead to the ignition time wandering around, which could lead to misfires.

Mark the position of the cam angle sensor (CAS) against the cylinder head.
Unplug the two cables going to it (for the magnetic pickup and hall effect sensor).
Remove the bolt holding it in place.
Pull it out of the cylinder head.
You'll see on the end a spring clip wound round the end which should be holding a metal dowel in place. On mine the dowel was poking out one end, and there were small bits of swarf around the drive and hole into the cylinder head. I poked the peg back in, cleaned it all up, put it back together, and then I had only a small bit of play left in the CAS disc. Ideally I would have replaced the dowel with a new one and replaced the oil seal too. Apparently a drill bit the correct diameter and cut to size will be a good replacement for the dowel.

Alternatively it could be your ignition coils (under the expansion tank). Check the resistance across the power terminals to it (I think this should be ~0.5 ohms) and the resistance between the two terminals on each coil (I think should be ~5.5k ohms).

Or, it could be your spark plugs - probably first thing to check, make sure the gap is correct.

Have a read of the engine management manual, I found it very useful in understanding how the system worked and what could be causing my problems.

[madbilly]

I measured the peg, it's a 3.96mm diameter (5/32") and mine is 20.6mm long, but it's a bit worn on one end so I think the normal size is 21mm long. I decided against replacing it with a sawn off drill bit but a 5/32" drill bit will fit snugly. the maximum length is can be 23mm otherwise it'll push the spring out.

[racerstev]

Mine had a problem with the injector plugs, drove me crazy until it finally
started missing at idle.

Also be sure the plug gaps are tight, try them down around .020..

Steve