Evening chaps,

usual boring cossie missfire help needed here

Basically over winter i fitted an unskimmed low mileage 4x4 head, along with a new crank sensor. and since then its had a missfire high up in the revs even when not under load sat reving in neutral.

i thought maybe the new crank sensor didnt like my alloy pulley so i fitted a standard pulley, but still no better.

To summarise what we have tried so far..

Dizzy rotor and cap
HT leads
New plugs on standard gap
Phase sensor gap
crank sensor gap
tried a brand new loom
tried different ignition amp

We tried a different ecu and chip with the old loom but need to try it with the new. its all thats left to try really!

group a coil was fitted only couple years ago.

The cylinder head wasnt rebuilt before fitting and has started weeping oil out the exhaust manifold gasket after a couple thousand miles. as well as smoking when i pull away in traffic, so defo needs whipping off now for valve stems and guides (its not turbo). i wonder if a dodgy valve could cause the high rev missfire?
Sometimes i can get a good few full boosts on road before the missfire starts, other times it happens first time I boost when not even up to normal temp.

I understand its a boring topic that comes up weekly here lol, but any pointers would be much appreciated..

Cheers.

 

Stick it on vipec with a new loom and leads if it's an electrical fault

 

Ha to be honest once ive eliminated it being the cylinder head causing the missfire I may just rip all the old management off and do that.

I'll be damned if i miss out another summer of driving the thing due to a bloody missfire!

 

Lol they do test us! Makes you wonder why we bother with them lol good luck with it!

 

Anything with a distributor and points needs junking, go vipec, coil on plug etc with a new loom. Mark Shead really rates the Emtron ECU and Rods loom is excellent.

 

Or go any aftermarket management that uses coilpacks

 

The mapper is more important than the make of ecu.

Mark

 

Cant argue with there mate - totally agree

 

Only reason I recommend vipec is most choose you to map it

 

Yes lots of choice for aftermarket management and may end up going that way if this issue continues.

Guess what i need to know is could a cylinder head issue cause a high rev missfire? doesnt do it on half throttle only full. seems strange the issue has risen since fitting crank sensor and cylinder head only.

Ram.

 

Book in to MA Developements and forget about it but be prepared for the bill, it will run perfectly after and go like stink

 

If this is happening under more than standard boost, this standard gap is a bad start.

Set to what?
Check distributor shaft end float too. theer should be zero.


Set to what?
Have you also tried new CPS and PPS?

 

As Stu as said plug gaps are the starting point gap at 0.6mm and try.
Might be worth doing a leakdown test and a comp test.

Good luck.

Paul

 

Fuel filter? Fuel pump? Start with the basics, maybe you've got some muck in there if old kit?

 

Hi Stu thanks for the response, ive replied in red below.


Thanks mate, Comp test came back fine. leak down test will hopefully be done by this saturday, but currently out of my hands.

Cant see it being that mate. uprated bosch pump with msd wiring kit. and filters not that old. also the fact the missfire has surfaced since fitting a 2nd hand head and a new crank sensor means its gotta be one of those imo.
Wonder if the new crank sensors faulty? still to try a different one.

 

Right guys thought id bump this back up for one last cry for help..
collected the car from Oddkidd unresolved as i had enough waiting, seems ill just have to persist with this on my own at home.

to add to the list of things done, the cylinder head has had a full rebuild.

All i have left to try is send injectors off to be cleaned, and try a different crank sensor incase the new one i fitted was a dud.

Spark plugs were set to 6.5, i closed the gap to 6 but no better.

Any other suggestions? the car drives perfect at crusing revs but from 5k upwards it missfires, even when reved in neutral under no load.

 

Have you tried a different set of leads? I had a car that misfired under very small load low down in the rev range. Every time I removed leads and refitted it was good for a few hundred miles. In the end I noticed the end of one lead was faulty. Replaced the leads and it was fine

 

You've gapped the plugs to 6 what?

 

phase sensor wire inside distributor worn?
new faulty cps, fuel pressure regulator faulty.
or TPS damaged when taking head off?

 

Yes fitted new Motorsport leads

Sorry that meant to read originally 0.65 now set to 0.6 but no better.

Still to try phase sensor but was running fine before taking it off the road. My mate gave me a brand new one to try but I've misplaced it! Will buy another and try as a last resort.

Brand new fuel pressure regulator fitted.
TPS was checked over and degrees set properly using pectal moniter.
I'm crossing my fingers and going to try another crank sensor. It was the only new part I changed before the misfire started!

 

Have you got one of them flash guards fitted under the rotor arm?
Just a thought......

 

What is the AFR before the misfire and what is it during.

Mark

 

I would def try another crank sensor if that's where your problems started from....
Even borrow one of another perfectly running car if you can?

Also what about pulling one lead off at a time and connecting it to a spark plug then revving the engine stationary and seeing if the spark disappears after 5k revs, trying each lead in turn?
If it does at least that may tell you what cyl the misfire is on if it's ignition/spark related

Cheers Paul

 

I would try dropping to 20 thou plug gap. 25 used to be ok but if something was up 20 could work better. 20 thou is 0.5mm

 

If the heads been off then the phase sensor alignment has been moved. I still say check that.

 

Is there a way of checking phase alignment using iaw? As the ecu will only compensate upto 4 degrees either way.

 

No mate not got one fitted

I know Jano road tested it with AFR system fitted but cant say i know what the figures were. Understand why your asking though as this would explain wether its a fuel starvation issue above 5k?

Not a bad idea mate, worth trying when im next with the car

Cant say ive heard of anyone running less than 0.6 but worth a shot to put spark plug possibility to bed

Just ordered your 4 sensor webber kit off your site. Will whack the new phase sensor in and check gap and most importantly fit the proper crank sensor.

I fitted a new cheapie one from that Brands Hatch performance company and cant help but feel its the cause, will soon know.


I took the saph out saturday and got a good 5 minutes of boosting up to the redline before the 5k missfire kicked in, so would make sense to be heat based? god knows really

 

Heat and misfire could be a dodgy ignition amp do you have another you could try?

 

Yeah tried a different one on the car but no different.
Revved it up in neutral today before it even got up to temp and the missfire still came in at 5k, so looks like I was wrong regarding temps being an issue, however booted fine in second gear when I took it out?!

Msd plug kit is sat at the post office depot waiting for me so will grab it tomorrow and hope the crank sensor cures it!

 

Fuel pressure reg set correctly? Could be leaning out

 

I know you said the GRP A coil isn't old but I had one fail and it was less than a year old. Worth a shot as you're ruling out bits one by one.

 

Have you checked the crank sensor plug ( loom side ) the pins can get wet and corrod up and course high end missfire like yours!

Also have you tried a new coil yet? you said yours is only a couple of years old but iv had 3 group a's die in less the a year!

 

Take it to someone that knows what they are doing is what I would recomend.
Is it on a stock crank pully.

Mark

 

Yep was set correctly using AFR gauge plumbed into downpipe take off, was checked on road

Possibility bud. I think Jano tried a different but i will borrow my mates one when i next see him to be sure.

Yeh checked and cleaned all plugs, we even tried a whole new loom so defo not a loom issue.

I was running an alloy one but switched to standard pulley recently on the hope it was a trigger issue, but no better.

After Ford Fair i will be throwing the towel in on my knowledge and handing it to someone reputable to try sort again. Just bought a new house so money is tight at the mo!


Thanks for all your input guys, i tried the fresh crank sensor yesterday hoping my last one was faulty but still no better. fitted and gapped new phase sensor tonight so will see how that works out on the way to silverstone. Camping tomorrow but as usual no track time sunday as every year my car throws in something new to make me hate it again lol.

Cheers chaps.

 

Did you get to the bottom of the problem ram? silly question but have you checked your map sensor? plenum for any air leaks, its definitely a strange one, had the misfire/ backfiring years ago when i had an ally pully on my first saph, fine when idling but bring the revs up it would cut and pop and bang, standard new pull from fords and it was cured, now i know these are hard to come by so 2nd hand seems the only route to getting one now days, i would just check that all four lugs are in good condition too