A good friend of mine purchased a 'S' Type V8 after working abroad for a good while as. tour rep (it was his treat for when he came back to the UK).

The issue that he has is that the car suffers a misfire.

Direct quote from email:

"I dunno which cylinder it is but it only misses between 1500 and 2500 rpm when accelerating gently. Boot it and it doesnt miss"

Car is an Auto and all spark plugs were replaced 2 days ago but still amiss. Mileage is 130k which is nothing.

can any one provide further assistance as the car is really very very well presented in its BRG paint work.

Many thanks in advance,

Stuart

 

Have you made sure the coils are good and water from the seal on the bottom of the windscreen isn't letting water down under the cowl and down on the motor. It will seep into the plug wells if they are not sealed. Oil seals can leak oil into the plugs also. I changed the valve covers and seals and sealed the covers over the coils. You can run water on the windscreen to check the seal..

 

It is hardly ever the plugs. Almost always one or maybe more than one coil. There are COP testers but usually you get an OBD code - and a cheap OBD tool such as an ELM327 at about a fiver from amazon or ebay is all you need.

Was there any dirt/oil/water/etc in any of the plug wells? Can easily damage a coil...

 

+1 to JagV8 - but, some misfires are so intermittent - they don't flag a OBDII code.

With 130K miles on the clock - it might be worth changing out the coils all together (about $300 for a good set of coils) I personally live by Jaguar OEM XR827823 or Motorcraft OEM coils - I now have 2 on stand by just in case...

I hear NAPA Echlin coils are good also - but never tried them and they have a warranty.

If that's too much - invest in a COP tester - about $80 on Amazon - test each coil at start up (60 seconds each coil) then at full warm up - same deal - 60 seconds each coil.

Odds are you will find the offending coil(s) - and don't be surprised if you find more than one intermittent failing coil.

Also, I hope you replaced the plugs with NGK double platinum plugs - anything else, your asking for trouble down the road....

Any traces of oil in that spark well - you will need to change the cam cover and spark plug well gaskets on that side. Good Luck!

PS - With 130K miles on the clock - you might want to find out if the tensioners were changed out - these engines are notorious for failing tensioners... could be the underlying issue regarding your misfiring under load...