C20XE Misfire

[BRoadGhost]

C20XE on 45's running a brand new ignition module, coil, spark plugs, electronic ignition; no air leaks etc.

The thing will misfire like a pro, but only when it's up to temperature.

Does this sound like a HT lead breaking down?

[scott.parker]

Is it like a stuttering similar to hitting a limiter at a set rev range, say 3,000 3500 etc?

As mine did this and turned out to be a faulty Coil pack (even new parts can be faulty)

[BRoadGhost]

Sorry that is to say it's on a distributor not coil pack electronic.

It will only do it after the engine's up to temp, so trying to nurse the thing home is tough when to get it to respond takes a heavy right foot. Part throttle / low rpm is the worst when it plays up.

[scott.parker]

Ahh, Iain had a similar thing to that on his track xe, I'm sure it was his inlet airflow meter, check on his thread, your describing the same thing he said.

[Iain]

Changing AFM did seem to improve it but mine seems to have come back Scott, still not sure what is wrong with it. Won't really help if he's running 45s though!

[scott.parker]

Changing AFM did seem to improve it but mine seems to have come back Scott, still not sure what is wrong with it. Won't really help if he's running 45s though!

Doh:tard::tard::roll:lol

[Will F]

compression test?

[BRoadGhost]

Just replaced the HT's and exactly the same issue. Sweet as for first couple of miles with no more than 10% throttle, then open it up and BAM misfires into stall - had to push it home.

I'll test compression as it's looking like the only thing at fault is the head gasket - what PSi / Bar is an acceptable figure or is it more that they should all be even?

[craig green]

A bit of a long shot, but I had an Astra GTE a few years back with a similar problem, it turned out to be an alternator earth issue. When it missed under load it would literally throw you into the windscreen.

Just try a jump lead from the alt adjuster to the battery negative terminal.

[edit] over 170 is healthy for comp testing iirc. obv all even(ish) is what you want.

[BRoadGhost]

Just done a compression test and there's some variance across the cylinders ranging from 140 - 190 PSi

That said the inlet manifold was painted & I'm not sure if I took enough away to get a proper earth for the alternator.

I suppose on the plus side, the new electronic ignition feels like a big improvement & there's some all singing HTs on the way...

[Paul]

50psi diff is big. What are they 1, 2, 3 & 4

[Bean,]

Agreed. If i had a 50 PSI diff i'd be removing the head to have a proper look.

[Will F]

How did you do the test - WOT?
And were the 3 pots 190 and one 140?

[swedge]

you should always do a compression test with wot (wide open throttle)

then do another test with adding a teaspoon of oil into the cylinder via the spark plug hole

if the readings go up on the wet test you have a ring problem lol