Wierd miss-firing fault.

[Markey Mark (BD)]

I've got a friends 5 gt turbo here that i have a strange miss-firing fault with that i can't seem to work out. It came to me for a service so i fitted new plugs, leads cap and rotor as usual, this didn't cure the miss fire so done a compression check and nothing looked out of the ordinary about 130-140 across all 4 pistons. No pressure in the oil system either.

I thought i'd take the head off anyway and have it checked to see if it was leaking past the valves and also to see if the liners looked scored or not, all come back ok. Fitted it all back together and the miss fire is still there, while checking the plugs i noticed one looks brand new like its never fired in its life (absloutley clean), i swapped it for another new plug still didn't fire, changed leads again and still didn't make a difference. The plugs sparking when out the car as i had all the leads with plugs in the sat on the rocker and could see a spark (just about as it was quite sunny). I've changed the cap for another one too but after this have run out of ideas, sorry for the long story but i have really hit a hurdle with this one.

[R5GTTRaider]

you didnt say if it misfires on idle or offboost or on boost,
try getting hold of a working aei unit, simple to take out, 3 plugs 4 fixings and a earth lead oh and the king lead

were you located as mine works perfectly


edit: just relised were you live
M25
76.5 mi 1 hour 37 mins

id love to help but its a bit far away to just drive,

[Markey Mark (BD)]

Miss firing all the time, tried 2 aei units still no difference.

[Os8472]

Firing order correct

duff rotor arm

tdc sensor knocked out of position

[Logg]

Have you tried changeing the TDC wire mate?

[Markey Mark (BD)]

I haven't tried a TDC lead yet but just find it strange that the plug is brand new like its never fired.

All cap and rotor is new and been changed again to eliminate them, TDC hasn't been played with since at all.

The thing is the plugs are sparking, i may try it later in the dark to see how bright the spark is as its abit hard to tell in bright sunlight

[Mart]

Is the inlet valve/pushrod ok? The plug might well be sparking, but if there's no fuel getting to the cylinder (if the valve is stuck shut), it hasn't got anything to ignite as such.

If the plug looks/looked 'wet' though, that's eliminated that problem from the equation...

[Markey Mark (BD)]

Is the inlet valve/pushrod ok? The plug might well be sparking, but if there's no fuel getting to the cylinder (if the valve is stuck shut), it hasn't got anything to ignite as such.

If the plug looks/looked 'wet' though, that's eliminated that problem from the equation...

I've had the head off mate and all checked out ok, i had it check to see if the valves were leaking but all good. When assembling it again saw all valves moving when i reset the tappets and all push-rods looked good. One thing i did notice is the plug was dry looking, not the normal wet look from flooding shall we say.

Its prob going to be one of those stupid faults but for the life of me i can't see it

[RICHIE]

what if the pattern on the fly wheel was damaged could this cause the problem with the tdc pickup

[R5GTTRaider]

Is the inlet valve/pushrod ok? The plug might well be sparking, but if there's no fuel getting to the cylinder (if the valve is stuck shut), it hasn't got anything to ignite as such.

If the plug looks/looked 'wet' though, that's eliminated that problem from the equation...

eaisest way to solve that would be to buy a colour tune set, but there not cheap. you could borrow mine ...but again if you were closer. tho id be happy to drive if you renburse me lol!!

so id say check which ones not firing and go from there, shame you cant have the car running with no rocker cover and see if that cylinder in qestion is pushing the rods down,tho if you remove the king lead and crank it i suppose no oil will piss out

then suppose try the tdc lead if all is normal

[Markey Mark (BD)]

Thinking along the lines of what Mart just said has anyone comes across a worn cam in a C1J before, wondering if the cam lobs worn so much the valves just doesn't open enough.

It may be a case of pulling the engine apart and diving alittle deeper into it soon.

[Markey Mark (BD)]

eaisest way to solve that would be to buy a colour tune set, but there not cheap. you could borrow mine ...but again if you were closer. tho id be happy to drive if you renburse me lol!!

so id say check which ones not firing and go from there, shame you cant have the car running with no rocker cover and see if that cylinder in qestion is pushing the rods down,
then try the tdc lead

Its Number 1 cylinder with the clean plug, i've run an engine before with no rocker on just for a second though to check valve movement before. Valves are all good as i saw them move when resetting the tappets.

[R5GTTRaider]

Its Number 1 cylinder with the clean plug, i've run an engine before with no rocker on just for a second though to check valve movement before. Valves are all good as i saw them move when resetting the tappets.

well thats dam strange, only thing it can be is the inlet valve mate, i know you said it moves but its a carbed of course so theres not even a inj that can be at fault,tho could be cam like you say

[Markey Mark (BD)]

I'm going to measure the lift on the cam lob on number one, i'm poss thinking a cam/follower fault possible after thinking about it abit more

[R5GTTRaider]

only thing it can be mate, if theres no fuel present, or not enoth then its unlikly to fire

[Mart]

One thing i did notice is the plug was dry looking, not the normal wet look from flooding shall we say.

If the other plugs were 'wet'/used looking from firing, and that plug was dry, there can't be any fuel getting to that cylinder, hence the inlet valve can't be opening. That, or something's been dropped through the carb and is diverting/blocking the fuel away from the manifold header relevant to that cylinder.

That would have to be some cam/follower wear to not allow the valve to open, but anything's possible with these engines!

Easiest way to check is to simply remove the rocker cover, and start the engine. Keep an eye on the inlet valve of the suspect cylinder to see if it moves/opens as much as the other inlet valves.

[Markey Mark (BD)]

If the other plugs were 'wet'/used looking from firing, and that plug was dry, there can't be any fuel getting to that cylinder, hence the inlet valve can't be opening. That, or something's been dropped through the carb and is diverting/blocking the fuel away from the manifold header relevant to that cylinder.

That would have to be some cam/follower wear to not allow the valve to open, but anything's possible with these engines!

Easiest way to check is to simply remove the rocker cover, and start the engine. Keep an eye on the inlet valve of the suspect cylinder to see if it moves/opens as much as the other inlet valves.

I'll pull the rocker off tomorrow and have another look, i'm sure it was ok but could of easily missed something.
Will let peeps know what i find.

[Sparkie]

i ran a cam for years with the top of one of the lobes totally worn off. - it was fine.

you will notice when that happens as you get the worst tappet noise, and you cannot adjust it away - the bottom of the follower becomes mushroomed, and the only way to remove it, is push it into the block....

it won't be that though.

has the car got a standard cam?
has the dizzy mesh gear been correctly positioned?
is the oxidation on the rotor arm and the pegs inside the dizzy cap, over to one side of the metal?

[Markey Mark (BD)]

has the car got a standard cam?
has the dizzy mesh gear been correctly positioned?
is the oxidation on the rotor arm and the pegs inside the dizzy cap, over to one side of the metal?

Car has a standard cam mate, looks like the engine has either never or hasn't been apart for a long time looking at the way the gasket was sealed to the block

As long as i've know the car the dizzy and gear has never been off the engine, rotor arm and cap are brand new but even from the few times it has run the points all look relativly ok.

[Sparkie]

pull the plugs out and crank the car over. if i remember correctly the fuel will spray out of the spark plug holes if the cylinder is seeing fuel. obviously keep the ignition leads away from the spray

[Sparkie]

incidentally, i reckon it could be the carb base causing your problems. either warped, or blocked in some way. and its chucking too much fuel in....

[Markey Mark (BD)]

incidentally, i reckon it could be the carb base causing your problems. either warped, or blocked in some way. and its chucking too much fuel in....

I've got a few working carbs here so i'll give one of those a try

[Markey Mark (BD)]

Right done a few more checks today.

Just to eliminate it i fitted another AEI unit, that didn't solve it so deffinatly not that.
Removed rocker cover and ran car and all valves are moving, i removed the plug and its still looking like new (not dis-coloured at all). Just to double check the spark plugs are firing a once again fitted a plug into the leads and held the against the engine, as well as seeing a spark i could hear the crackle it gives off to so its sparking.

Looks like its now an internal fault, i've informed the owner who is now considering trading it in on the new scrap scheme as he needs a car for work asap
If it does come to this i'll be stripping the good bits off it and fitting some crap stuff on so it won't all be waisted (has to be a running car to be accepted)

[stuTHC]

have you had a meter on it and checked the fuelling. Surely the 2 main causes of a miss-fire would either be spark or fuelling, you've ruled out the spark so..........

[Markey Mark (BD)]

have you had a meter on it and checked the fuelling. Surely the 2 main causes of a miss-fire would either be spark or fuelling, you've ruled out the spark so..........

The thing that gets me is its firing nicely on the other 3 cylinders but number 1 is dead, doesn't seem a trace of mixture in the cylinder as the plug is as clean as a wisstle.

[Brigsy]

Daft question is the manifold gasket ok? Air leak on that cylinder? Any cracks in inlet manifold (doubt it will but never say never?)?

[Markey Mark (BD)]

Daft question is the manifold gasket ok? Air leak on that cylinder? Any cracks in inlet manifold?

Changed the gasket for a new one when i fitted the head back on mate, i'm tempted to pull the manifold off to check it and look at the ports in the manifold and head

[Mart]

Is/isn't there fuel getting to that cylinder? You really need to confirm that before anything else.

It's not gonna be the carb, aei, sparkplug, or anything along those lines if there isn't any fuel reaching that part of the engine.

[Markey Mark (BD)]

Is/isn't there fuel getting to that cylinder? You really need to confirm that before anything else.

It's not gonna be the carb, aei, sparkplug, or anything along those lines if there isn't any fuel reaching that part of the engine.

I'm pretty sure its lack of fuel to the cylinder now as you say mate, thought i'd double check as i was second guessing myself today

I'll be honest i'm not sure how i would check if fuel was going to that cylinder on its own, being carb the mixture is being spread over 4 cylinders so not all being directed into just one. Plug is dry so i presume it's not.

[Sparkie]

pull the plugs out and crank the car over. if i remember correctly the fuel will spray out of the spark plug holes if the cylinder is seeing fuel. obviously keep the ignition leads away from the spray