Land Rover Repair: 96 disco- Misfire, spark plug wires, auto electrician

Question
LR already replaced all the plugs and wires, do you think I should try the coil pack before the valve job?
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Followup To
Question -
I am original owner of a 96' disco with 91k miles.  For the last year I have battled the check eng light mystery due to eng misfire.  The LR dealer has replaced several items, but the light always comes back.  It was serviced this Jan, with a tune up and they flushed the valve sys.  Now LR is telling me I can either replace the coil pack or go with the Valve job.  My disco always starts up, but does start bucking around 50mph and hesitates until she kicks-in.  I'm not sure which route to take. I have already spent thousands.
Andrea
Answer -
Hi Andrea,

I had some trouble with my '95 Disco that sounds like your problem. Turns out that three (3) spark plug wires were not firing properly.  I've replaced them and the Disco runs fine.  

Could be a coilpack problem...but its rare.  You can find a salvaged coilpack at www.car-part.com and they are priced from $50 to about $200. Try a salvaged coilpack and if its not that ... consider the valve job.  Turns out that even older Disco's can suffer from the sticking exhaust valve that faces most Disco II's.

Best of luck,

JohnMc

Answer
Hi Andrea,

a local auto electrician can do a bench test to see if coilpack is at fault.  Better to test it than just replace it...unless you buy a salvaged one as I have suggested.

Bench test by a local garage might cost you as much as a salvaged coilpack.  Something to consider.

If you've been having misfires for some time, it may be the exhaust valves sticking.  A cyl. pressure test could reveal this problem.  Try to avoid a $2500 valve job ... but its bound to surface on older high mileage LR's.

Best of luck,

JohnMc