OK, I have a missfire on my engine at all revs including idle. Cyls 2 and 4 not running at all - see vid here http://uk.youtube.com/watch?v=xwE1LD4XrO0 You can hear the difference in the exhaust bypass too.

Diagnostics so far:

 

Compression test - all cyls 16bar

 

Removed sparkplugs from engine and grounded them. Turned engine over and all plugs sparking.

 

Manually shorted ECU outputs to check each coil on correct output - OK

 

Manually shorted ECU outputs to check each injector on correct output - OK

 

Increased coil dwell time - no change.

 

Ran new heavy gauge +ve/-ve lines directly from battery to coils. No change.

 

Swapped coilpacks from 1/3 to 2/4 - missfire still on 2/4

 

Swapped injectors from 6/8 to 2/4 - missfire still on 2/4

 

Swapped ignition modules from bank to bank - missfire still on 2/4

 

Swapped coil sub-harnesses from bank to bank - missfire still on 2/4

 

Changed sparkplugs - no change

 

Any ideas greatly appreciated, it's really annoying me now!!!!

 

I'm beggining to wonder if it's something physical, maybe the injector angle is off on these 2 cyls and the fuel is running down the manifold wall instead of entering the cyl as a mist or something. Will need to investigate more when I get time.

If I enrich the mixture on all cyls then re-connect the injectors on these 2 I can get some spitting back like you normally get through the intakes with a too-lean mixture.

Is it missing to the extent that removing coil packs from plugs makes no differance

Does the engine run slightly better or the same if the injector connectors to the offending cylinders are left disconnected?

 

Jeff TT

Removed sparkplugs from engine and grounded them. Turned engine over and all plugs sparking.

 

Surely if all 8 spark plugs are sparking when held against the block then the misfire isn't ignition/coil pack based, it's fuel based?

could it be a ignition timing issue ? meaning ignition timing is off for cyl 2/4.

Have seen this happen before on other aftermarket ECU's (eg. AEM, Autronic), becuase of an incorrect CAS setup within the software or in some cases because of a firmware issue within the ECU.

 

-Eric

Yes missing to that extent!

Removing the injectro plugs makes NO difference at all - see in the vid I pull them off at the start.

Yes, they were all sparking but had wondered if some of the sparks were just too weak. Seem to have eliminated that now though by all the swapping around.

Timing off is a possibility but it's fired wasted spark and the paired cyls are working OK.

1 8 7 3

6 5 4 2

 

Think I'll get an oscilloscope on all the connectors and see if I can see a difference between them. Also try some easystart down the runners of those 2 cyls and see if that brings them up temporarily.

I know this is probably a very stupid question but you have got the two connectors the right way round so they're not firing when the other should be firing?

I know this is probably a very stupid question but you have got the two connectors the right way round so they're not firing when the other should be firing?

 

Lol, yeah, I point-to-point checked all the wiring from ECU to coils/injectors.

Yes missing to that extent!

Removing the injectro plugs makes NO difference at all - see in the vid I pull them off at the start.

Yes, they were all sparking but had wondered if some of the sparks were just too weak. Seem to have eliminated that now though by all the swapping around.

Timing off is a possibility but it's fired wasted spark and the paired cyls are working OK.

1 8 7 3

6 5 4 2

 

Think I'll get an oscilloscope on all the connectors and see if I can see a difference between them. Also try some easystart down the runners of those 2 cyls and see if that brings them up temporarily.

 

If a squirt of petrol or easy start brings them back into life it does sound like fuel.

 

You could have a look to see if there's a physical defect with those 2 throttle bodies injector seats, maybe a burr or a hole drilled too small or even an o-ring that's pinched?....... I'm struggling to be honest.

 

But I got a good V6 here if you need it? :D

Just to summarise, just so ive got this straight in my head:

 

Compression - Good

Spark - Good

Timing - Good on offending cylinders paired cylinder

Fuel - Good on all other cylinders

 

Im sure youve probably already checked john, but when you remove the spark plugs, are they soaked in fuel?

 

The only thing that i can logically think of would be an injector fault, being that either their not spraying at all or they are perminantly open?

 

Sorry i cant suggest anything new or unthought of.

I was thinking might be worth swapping injectors and seeing if it changes cylinders or even unplugging each one individually?

I was thinking might be worth swapping injectors and seeing if it changes cylinders or even unplugging each one individually?

 

he's already swapped the injectors though.

whoops :)

If a squirt of petrol or easy start brings them back into life it does sound like fuel.

 

You could have a look to see if there's a physical defect with those 2 throttle bodies injector seats, maybe a burr or a hole drilled too small or even an o-ring that's pinched?....... I'm struggling to be honest.

 

But I got a good V6 here if you need it? :D

 

Yeah, think that's most likely, maybe an edge not machined between the injector boss and the runner or something. Will strip it when I get time (working away again until end of month :mad:) On the road for March is looking ever more unlikely!

 

Good V6, what for, an anchor :tongue:

Tell me about it, money is holding me back now. Soooo close to finishing mine now and i need a month to run mine in really because it'll be freshly rebuilt :(

 

How i'm going to put 3000 miles on in 4 weeks before the 2 track sessions i don't know!

I just had a thought..........

 

Could you move the two ITB's to other cylinders and see if the missfire moves?

 

I know it might be a pain with the linkages and all that.......

I just had a thought..........

 

Could you move the two ITB's to other cylinders and see if the missfire moves?

 

I know it might be a pain with the linkages and all that.......

 

No, because the injector is fitted into the manifold, not the TB its self. Could swap the manifolds side to side but if I remove one, hopefully I can spot the problem.

out of interest, what was the problem here?

out of interest, what was the problem here?

 

From other site :

 

think i've finally managed to pin down the missfire!

Got the 'scope on it today.

Looks like the last firmware upgrade i did to the ecu to change a pwm output table to a digital has screwed up the firing.

Compared a coil firing signal off a 'pair' of cyls where both were running with a pair where only one was. Guess what, the pair with the missfire was only firing 1/2 as often!

Guess that no 2, 4 cyls are only being fired on the exhaust stroke! Will get in touch with emerald on monday, am sure they'll fix it quick but annoying how much time i wasted finding it. Hadn't appreciated just how uesful a 'scope can be on a car.