Hesitation at 4k and over when warm

[Jojo]

Hi

Thanks for your reply, again.

Ok so did some further investigation hoping to eliminate some of the possibilities:

Noticed that at idle sometimes engine stalls as idle is sometimes hunting and rough.

TB is clean as a whistle.

Unplugged the MAF, engine still hesitating at 4500 and over, so probably MAF is not related.

Noticed that there is a small difference when the oil cap is removed, in fact engine revs go up a tiny bit however engine still hesitates with the oil cap is off and engine revved up to above 4500. so probably AOS not involved too.

Hot engine makes it needing more turning to start it up, but starts. Driving no further than approx 4500 rpm car seems to be fine.

So my next guess tends to be pointing at a defective coil/spark plugs so might need to inspect physically each one and see...

JJ