Thread: A Classic Misfire

Originally Posted by Rayngie

Hello,

my 88 3.5v8 has developed a misfire, started last weekend with missing when cold that went away when warmed up, now it's just missing all the time, i'm just wanting to know where to start looking for something wrong ( preferably, opening the bonnet and finding a switch for 'misfire ON/OFF").
I am a mechanical numpty, all i know is that usually, i turn the key, Voodoo happens, and i drive off.

Anything obvious to look at?

the car is well maintained, never shown any signs of problems, the leads etc all look new ( had the car for almost a year and a half ), and generally runs very well.

Any idea's welcome,

cheers,

Ray

The best time to look for misfire problems is when its dark. Open the bonnet with the engine running and you may see sparking at a crook lead. New doesn't mean good, sometimes a lead will fail early. If you see no sparks you might need to go for new plugs.

are all the spark plug leads pushed nice and tight into the dis cap and onto the plugs

cheers guys,

i'll have a look in the dark..you never know.

and yep, all nice and tight, i did find a loose plug, tightened that up and made no difference..

probabley leads and plugs.

Have a look at this . I just posted it on another thread.

How to Test an Ignition System

Regards Philip A

Originally Posted by Rayngie

Hello,

my 88 3.5v8 has developed a misfire, started last weekend with missing when cold that went away when warmed up, now it's just missing all the time, i'm just wanting to know where to start looking for something wrong ( preferably, opening the bonnet and finding a switch for 'misfire ON/OFF").
I am a mechanical numpty, all i know is that usually, i turn the key, Voodoo happens, and i drive off.

Anything obvious to look at?

the car is well maintained, never shown any signs of problems, the leads etc all look new ( had the car for almost a year and a half ), and generally runs very well.

Any idea's welcome,

cheers,

Ray

G`day Ray ,

If it`s missing all the time you`ve already had a win as far a finding the problem goes although not so with fixing it .

I`d suggest you go along and check each cylinder to narrow down where the problem is .

Find a spare spark plug of any variety , even from a lawn mower that will fit into the leads to check for spark .

Start the car and memorise the sound of the miss in the engine and look at how the engine moves or shakes with the miss . If you don`t see the movement put you hand carefully on a rocker cover and feel it .

Remove each lead in turn , one at a time and fit your spare plug which needs to be earthed .

Start the car and listen to the miss and look for a spark .

If the miss sounds worse it means that cylinder is working .

If there is no spark that cylinder is the problem , as in that lead or sparkplug ETC .

It is time consuming but will locate the problem area and if your lucky you`ll find it at first or second go but it may take eight and it can be done by anyone fairly easily .

If it turns out it is a valve or cam fault ETC this will also help in substantiating which or where .

If you choose to do it and need more information just ask .

Cheers

My bets are on the coil...

well, poked and prodded around yesterday, all still the same, i'm going to order a kit of stuff from Gary @ CLR ( plugs, leads, dist cap & coil )and stick it all in and see what happens....need to go away in it next week surfing on a stagg do!

will report back,

Ray