Mx5 1.8 nb runs rough and stalls after driving on hot day

[hks_kansei]

One think I did notice I when I was pulling the leads off (from the spark plug ) while it was running rough to see how it effected it was that when I removed one of the leads sparks fired from the top of the lead where it meets the coil unto the side of the coil .. could it be the lead failing ??

It certainly could, leads will often degrade long before they start to visibly arc from the insulation.

I would most certainly replace the leads, i'm shocked actually that it wasnt suggested as the very first thing to check!

When you change the leads also change the spark plugs, if the engine has been misfiring it is pretty much certain that at least one plug has been fouled. You can clean fouled plugs off etc, but I would personally suggest just replacing all 4 with new ones (narrow the problem down some more, plus it's only $20 for a set of plugs)

[Mr Morlock]

you might want to think about getting the car checked by a mechanic for testing and diagnostics - the smart guys can often find a fault bucks they know what to look for- you cannot actually rule out a coil if you replaced it with a second hand unit. Coils can be checked as can leads e.g. Performance Ignitions in Melb and from memory its no charge. You may have already replaced 2 of the sensors without anything being wrong with them. I would have thought if it was leads then the misfiring would be there all the time not just hot- but thats a guess not a fact. Incidentally the model of your car is on the VIN- its critical.

[hks_kansei]

I would have thought if it was leads then the misfiring would be there all the time not just hot- but thats a guess not a fact. Incidentally the model of your car is on the VIN- its critical.

Generally that is the case, however if a lead is arcing through the insulation it should be replaced, regardless of if it is or isnt causing other issues.


Performance Ignitions are a good choice, as from memory, they are a distributor for Magnecor leads, which I have found to be very good. (mine are about 10 or 15 years old now and still test perfectly on the multimeter)

[bebop71]

Thanks again to everyone for there input I have taken the car to a mechanic .. He lives just down the road and as its intermittent he is going to have a look at it at his home ( very awesome of him ) will know more Sunday fingers crossed

[bebop71]

ok so have given it new plugs and leads and so far so good have done about 400km in it and the problem hasn't surfaced so far so hopefully all good

Thanks again for everyone's in put