Help diagnosing rough running/misfiring

[sladey]

My car has been running brilliantly for a while now. Faultless and pulling like a train.

Until tonight. On the way home I accelerated hard up towards the red line (not unknown behaviour) and it started pausing and jerking along the way.

I considered what it was doing for the rest of my journey:-

At idle and low revs all is fine
when accelerating beyond 2K RPM it jerks and doesn't accelerate smoothly - I'm frequently getting bangs which sound like ignition within the silencer. When I push beyond that it's definitely lost power - like it may be running on 5 cylinders

When I got to my destination I had a look at the engine - initially just looking for loose plug leads and loose connections to the coil packs - several of the plugs were able to be pushed in a bit. ON the way home though nothing had changed.

TOnight I hooked up the laptop and took it for a ride around the block to record what was happening. I've excluded trhe oxygen reading from this screenshot because it hides most things (don't know it's part of the problem or not)

If you look at the red line (revs) in this one you can see the jerking as I'm trying to accelerate


Here's one with the oxygen reading added back in - looks pretty wild. I don't know if that's pointing to a problem or normal



Any suggestions of where to look, what to check next to help diagnose the problem would be gratefully received

Cheers

Mark

p.s. Red= RPM
Green = Load
Black = engine temp
yellow = air temp
Blue = voltage
Orange = pulsewidth
pink = advance

[Gary71]

Morning Mark, Can you remind us what fuelling/spark set up you are running?

[impmad2000]

Spark missfire ? possibly from ignition leads ? take a look in the dark ! O2 readings go crazy on spark misfires as they suddenly see unburned fuel instead I'm of combusted gasses.
it sounds similar to how mine goes if I get water around a spark plug lead.

[sladey]

Thanks Tim.

Gary it's all a canems setup I've got two coil packs instead of a dizzy, canems ecu (hence why I could produce the readout), and canems replacement throttle position sensor and MAF replacing the barn door

As I say it's been faultless since January every day until the other night

[sladey]

Update - it was simply that an ignition cable had come loose - I had checked them first off but obviously when I was pushing it in it wasn't seated properly so I wasn't pushing against the right thing.

I went to look at the plugs and it was hanging half out. Pushed it in properly and all is good.

If only all my problems were so easily solved.

Thanks for the replies

[neilbardsley]

As you said if only all problems where so simple

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