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[TECHNOPUG]

Is there any way of diagnosing a misfire, other than just changing plugs, leads, DIS, crank sensor etc?

The cam cover gaskets need replacing, so I will replace the plugs at the same time. But it could work out expensive if I have to change the leads, then the DIS only to find that it's the crank sensor. Any ideas/suggestions people?

[JamesV6CDX]

To get an idea re the crank sensor, check for code 19 stored.

While you're doing the gaskets, change the plugs as a matter of course.

From there, If you want to see if a given HT lead is firing, you can attach a strobe to it and see if it flashes.

If you don't get any flashes on any given lead, substitute it for another lead and try again. If still nothing, suspect the DIS.

Remember HT related misfires won't log codes on non DBW engines.

Failing that, out with the compression tester!

[TECHNOPUG]

Yep - plugs to be changed as a matter of courses. Compression test is easier enough for me to do too.

Misfire only occurs between 2.5-3.5 revs when engine is under load - like pulling from 60mph in 5th. Once above 3.5k all is fine again. Also at low speeds/gears when engine isn't under a big load (such as in town) there is no misfire. As much as I would like to change the plugs whilst the TB is off giving easy access, I'd really rather not have to fork out £120+ for parts that aren't at fault!

 Re: the strobe test. Surely if one lead wasn't firing, I'd be running on 5 cylinders al the time - ditto the DIS pack? Will try the paperclip test to identify whether crank sensor is playing up.

[JamesV6CDX]

Ah - if it's missing under load that's different.
 
It's almost guaranteed to be HT related... look for a broken plug insulator.

[TECHNOPUG]

Ah - if it's missing under load that's different.
 
It's almost guaranteed to be HT related... look for a broken plug insulator.

Rubber insulation being degraded by oil in the plugs from leaking cam cover gaskets?

[JamesV6CDX]

Ah - if it's missing under load that's different.
 
It's almost guaranteed to be HT related... look for a broken plug insulator.

Rubber insulation being degraded by oil in the plugs from leaking cam cover gaskets?

Got it in one

[TECHNOPUG]

That was always my initial suspicion, it was only through reading other posts on here that lead me to investigate other possibilities.

So an inspection of all the lead is required. Could it be that the leads are fine but oil is corrupting the contact between the lead and plug? Or will it be obvious upon inspection that a lead is at fault?

[TECHNOPUG]

Just ran a paper-clip test and no fault codes came up, so that's something I guess.

[bth2bth2]

hi,
having a similar problem with my mv6.missing under load etc.had to give it to a mate to sort after the fault dissapeared then reapeared only worse.the only code stored is a temp sensor code.its had new plugs and leads when i did the cam gaskets so me thinks its the dispack.would i correct in asuming such or would a faulty temp cause a bad miss fire?
just a note,the EM light would flash on but not stay on for any length of time.
sorry for the hijack.
cheers all
brian
 

[JueV6]

When i picked up the mv6, it had a missfire on idle, cured itself at 2.5k then reapeared at 3k  DISS was knackered. fitted replacement and it was fine.