172 Cup Misfire from 5000rpm up

[gek]

Hi all,

My Cup has developed a misfire above 5000rpm.
Starts fine, idles fine and if it weren't for me pushing above 5k every now and again I'd never even know there was a problem as below 5k everything is fine.
What's the order to check stuff? TDC sensor (worth cleaning or just replacing, along with the loom too?), plugs, leads, coil pack, anything else?

Any help much appreciated.

George

 

[Dunn]

Check you have the correct plugs in, or buy a fresh set to be sure

make sure they are the NGK PFR6E10

 

[daddycool]

i bet you've got bosch spark plugs in there and not ngk :approve:

edit: beaten by seconds

 

[Dan1587]

i bet you've got bosch spark plugs in there and not ngk :approve:

Does that really make the difference?
The ones quoted above, are they the 'Lazer Platinum' ones, as i've just bought a set and hopefully i've got the right ones!

 

[daddycool]

yeah mine said platinum on the box i think

 

[gek]

If I remember I've got the NGK ones in there but I haven't changed them for a couple of years.
So that would be the best thing to change first? I'll get a fresh set and report back!

Thanks
George

 

[daddycool]

a world of difference, mine misfired between 5-6k rpm until i took the bosch ones out and put correct ngk ones in. a shame, as ngk are four times the price of the bossch ones!
bit of a pain to change though as you have to remove the inlet manifold. not difficult, just a bit long winded as you have yo either disconnect pipes and plugs or balance it precariously.

 

[gek]

Just a question regarding removing the inlet manifold - do I need to replace the gasket?

 

[daddycool]

no you don't need to as it's just the upper inlet you are removing.
if you ever remove the lower inlet you need to replace the inlet-to-head gasket.

 

[Jonny1*2]

hopefully this is just plugs and not timing issues. Have you thought about having it plugged into diagnostics?

FYI ebay for the NGK plugs are £30 delivered

 

[gek]

If it had slipped a tooth would it run so fine under 5k? Maybe I'll get it scanned before I get the plugs.

 

[bmh.01]

I'd go with ignition related here all day long. Either plugs or a weak coil pack.

 

[gek]

Coil pack was the culprit. All sorted now. Thanks all for your help.