Misfire - Ghost in the machine

[dunlopstar]

Ever since i renewed my spark plugs (NGK) a while back, my engines had an everlong misfire in chambers 1 and 3.
Its worth noting that before i changed the plugs, the engine misfired now and then.

I have tried several obvious fixes so far:
Swapped plugs back
Renewed coil packs
Got Injectors 1 and 3 cleaned

The HT leads work no matter what plug there connected to so i figure there working good enough.

Any suggestions are welcome cause this is a freakin constant pain!!

Cheers

 

[Chapster5]

Slight split in the head gasket? Has it lost any power?

 

[dunlopstar]

Yeh, barely holds the revs, when you take your foot off, it just dies once the revs go down. Struggles to stay alive

 

[Chapster5]

Have you done a compression test on all cylinders?

Should be your next step mate

 

[dunlopstar]

True that, ill have to check it out!

 

[Chapster5]

Let me know how you get on

 

[dunlopstar]

Ok finally got myself a compression tester. Chambers 1,2 and 4 are firing normal at 12 BAR and slightly above. Chamber number 3 though is only running at 10? Problematic difference?

 

[MicKPM]

That's not ideal then... I assume that was a 'dry' test and that you've not carried out a 'wet' test yet? If not, Pour a small volume of engine oil into each bore, one at a time, and repeat the compression test on that cylinder. If those readings increase, it shows there is wear in the compression rings aka "blow-by". If they don't really alter at all the problem is likely to be a leak in the head gasket itself or the valve seats are shot... either way the cylinder head will have to come off.

 

[dunlopstar]

A wet test? Put a bit of oil at the bottom where the plug or tester screws in?
If it has to come off thats fine, ill get to clear the no doubt massive amount of deposits lining the head.

 

[MicKPM]

Yep, remove the spark plugs and then pour the oil in to the cylinders, one at a time, via the spark plug well... then repeat the test one cylinder at a time. You don't need too much oil though, just a teaspoon or two at most. Obviously it wil smoke a little to afterwards but don't worry as it will burn off fast and won't damage the CAT.