P38 4.6 rev problem

[cerberatony]

the problem i have is that driving normally all ok,
sometimes when driving 40mph and auto revs drop to about 1300 i get intermittant lumping, hesitation.
if i want to rapidly overtake something all goes well untill revs get to about 3500 to 4000 then it feels stiffled hesitant and seems to start missing, basically i cant get over 4000 revs underload. i feel this might be a faulty coil or too loosing power at higher revs. what do you think?

[eliot]

How much fuel is in it? Mine does that due to cavitation well before the light comes on, in fact its the last line before the light.

[cerberatony]

sorry didnt mention its the same on lpg or petrol so ive illimated fuel, thats why i think its electrical

[D4MJT]

Good basic places to start mate:

Check the plugs, are they clean, when was the last time they were changed? Has it got Champion plugs in it? Mine is VERY fussy about having Champions in, and runs like a dog compared with normal on anything else.

What state are your HT leads in?

Is your car a GEMS or THOR engine? What year is it?

If it's mis-firing under load, and hesitant when cruising, I'd probably also be checking the MAF sensor, that could be the culprit. As you say, if it's showing the same symptoms under both LPG and petrol, I'd probably leave fuel for now.

[cerberatony]

its a 2002 thor engine with new magnacore leads plugs good but someone else suggested maf so i ordered one hope this cures it.

[cerberatony]

fitted new maf sensor today and what a difference, pull away is what you would expect for a 4.6 although i still have a problem higher up rev range so because i am on lpg i will cut my cats and remove the inners. these i have always believe to be giving me problems and it wont cost anything to find out.