friends 450 bhp harvey engined focus has a misfire,
fine under 20psi of boost. fine up to 30psi till it gets to running temp.
on p8 ecu,, and same with a L8.
fairly new engine loom all new sensors, had few sets of different plugs in it, new leads cap arm phase etc etc, pectel monitor says all ok.

 

sounded a bit spluttery up knockhill yesterday
seemed to clear now and again
just seemed to do it under load
sounded like dodgy spark somewhere but you've already changed everything?
whats the plug gaps?
i had jamie's right down to .6mm to stop the splutter on high boost

 

we've had them down to 23 thou which is about the same

 

give the old chap a ring tomorrow andy

maybe its a boost limit in the chip, easily changed

 

i seen it yesterday
it seemed to clear sometimes so cant see it being boost limiter

 

Bit of a long shot and you've probably done it - but check all the earth straps

 

sorry didnt read your post as said andy give him a bell

 

Jimbo its charlies old engine it never done it then & the chip hasnt been changed or that

 

what about fuel probs ? does it have a decent tank or swirl pot system. we found with the bastos car he had missfire problems because of no swirl pot system ! and the fuel pump was getting gulps of air in cornering

 

would that make it misfire will?

 

Think the tank will be sound it was fine when andy had that focus when it was 618 bhp

 

same fuel set up as i had when it was 620 bhp using only one high pressure pump supplied from swirl pot fed by two red tops, and it doesn't need a corner

 

yip even stuck an extra one on the head

 

even tried a new pump

 

Map sensor been swapped andy ? when i was speaking to kenny out the back tonight i forgot to mention it

 

New loom sounds like the issue to me.

 

was a new one we stuck on it, and reads fine on the monitor

 

with these cars the way they are that would be verry easy to check

 

its ran mint on it before, its been on there from new and never gave a problem

 

He said to me today that he found a dodgy pin for the crank sensor i think , might be worth unplugging every sensor one by one & checking all the pins. Bet its something daft

 

would alternator cause interferance/ voltage spike?

 

have you data logged it and downloaded it to see what everythings doing when it misfires, poss voltage drop?

 

Had something like this once, has it had a new ignition amp? if so there needs to be lots of heat cream between it and the alloy mounting plate. Otherwise the amp over heats and causes a misfire or even shut down!! Its ok when cold, but it would get worse as the motor warmed up! In my case it had me goin for a while!!
Cheers....

 

i had similar trouble with mine ages ago
in the end i found that a pin in the connector to the coolant temp sensor had slipped down, it was still in the plug but had come off of the sensor itself so wasnt reading any heat
its got to be worth a check.

what about plug leads?

 

nope not tried that
be good to get it on R/R and get a scoope on it to monitor voltage and signals

 

its mint we had break out lead in there checking it all

 

the amp is on a new ally plate and pretty sure there will be no heat cream!

 

can you not just take it out on road when it misfifes stop the data logging and download to laptop and see what its doing?

 

collapsing lifter when the oil viscosity changes, would account for an intermittant missfire.

 

don't have the shit to do that...

 

they were new,, doesn't mean they ok thou

 

you not use solid ones

 

not in that engine

 

Whilst the term heat cream is amusing, could you clarify whether there is thermal heat sink paste being used, similar to what computer CPU's use between the heatsink and chip. If you don't the thermal heat sink paste between the ali plate and ignition module will be next to no heat transfer.

Rob

 

Have the injectors been flow checked? Maybe dodgy spray pattern on one?

 

any joy?
always nice to know of things to check if you get a miss

 

nope tried another amp and plate tonight from another car

 

it might be worth you investing in a copy of the IAW Monitor software that Stu sells as it will datalog and scope making it easy to find problems like this. for the value of the engines that you play around with, it's a very small price to pay for full diagnostic facilities

 

get Carlo to take it to AVA