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Missing - New spark, leads, coil, DFI - ideas?

Stramec

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Hi All

So my VY has decided to start missing and juddering. Assumed it was a dodgy spark plug, as they were due to be replaced, put in new sparks and new leads. Same problem.

After reading this fine forum I tested the coils and found the 1 & 4 coil had no spark arching on it. So thought super easy quick replacement of coil. Same problem.

Must be the DFI is shot. Just replaced that this morning, left the 1 & 4 leads off, and the coil sparked, put them back on, started the engine... Same problem.

Took the leads off no spark arching on the 1 & 4 coil. As the problem is remaining constant either something is frazzling the DFI almost immediately, or it's being caused elsewhere.

So now I'm at a bit of a loss. The engine starts ok, it judders a lot, especially under load. The other 4 cylinders seem to be working fine. So from my brief knowledge I don't think the CAS can be screwed.

I have a Tech2 and that is showing no error codes, I'll try the paper clip test, just as a hail Mary.

I cleaned the connector to the DFI, looks ok.

The only other thing is intermittently I'll get a dashboard alert that there is a fuel gauge error and I should contact the dealer. - I don't see how this could be related to one coil not sparking, but it's there just in case.

Would greatly appreciate some suggestions as to what to try next.
Cheers
 

_R_J_K_

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Did you chase the DFI loom back to see if any of it was freyed or damaged? Does the plug look in okay condition?

I know you bought a new coil, but just to eliminate the new one being faulty too does the miss change cylinders if you swap the coils around?

Also unlikely, but it might also be worth taking the rocker cover on that bank off to see if there's a cam issue (very unlikely as all other cylinders work) or anything wrong with the rockers, push rods, or valve springs. If you take all the spark plug out and turn it by hand it should be pretty obvious if anything's up.
 
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losh1971

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Try replacing it with another coil pack
Even if you just try switching around the coil packs.
 

Stramec

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Try replacing it with another coil pack
Even if you just try switching around the coil packs.
Hi - I tried that, the working coil fails in the 1&4 position, and the non working one fires in the 2&5, so I think the coil packs are ok, something further upstream, causing a rick.
 

Stramec

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Did you chase the DFI loom back to see if any of it was freyed or damaged? Does the plug look in okay condition?

I know you bought a new coil, but just to eliminate the new one being faulty too does the miss change cylinders if you swap the coils around?

Also unlikely, but it might also be worth taking the rocker cover on that bank off to see if there's a cam issue (very unlikely as all other cylinders work) or anything wrong with the rockers, push rods, or valve springs. If you take all the spark plug out and turn it by hand it should be pretty obvious if anything's up.
Thanks for the tip, will embrace that tomorrow, had a cursory glance at the loom, didn't seem too bad. Does each coil pack have it's own wire for a firing signal? That would certainly make sense as to why it's just that one position.

Moved the coils about, the problem stayed in the same place, so think coils are fine. Can't believe I'd get two dud DFIs in the same spot, so going to guess that is ok. I'll try taking off the rocker and cranking it over without the sparks, if nothing obvious looks wrong with the loom.

Cheers
 

_R_J_K_

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Thanks for the tip, will embrace that tomorrow, had a cursory glance at the loom, didn't seem too bad. Does each coil pack have it's own wire for a firing signal? That would certainly make sense as to why it's just that one position.
Something to that effect, yes. Do the plugs end up getting covered in petrol? Just ruling out the injectors not firing.
 

Stramec

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Something to that effect, yes. Do the plugs end up getting covered in petrol? Just ruling out the injectors not firing.
I think you are right, that it may be the injectors.
I traced the wire loom nothing obviously out of place. Then I checked the injectors. The resistance across them all was the same, and the live current on the connector was steady, as was the pulse signal with the engine running on the earth wire. So I think the electrics to the injectors are all fine, however the two spark plugs from the misfiring coil, were bone dry.

So I guess now my question is, is it feasible that a faulty injector would cause the ECU to shut off the associated coil?
 

_R_J_K_

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Doubt it, plus if the ECU knew an injector was faulty it would probably throw a code.

I don't really know what that means for you as it seems unlikely two injectors would die (but not impossible), but as a litmus test I would take all the leads off and crank it a few times and compare the plugs from the firing cylinders to the missing cylinders for petrol. If that gives you some info, I guess the next PITA step after that is to move the faulty injectors to different cylinders and see if they do it in different cylinders too (at least you don't have to put the upper manifold on to do this). That should be pretty conclusive.

Nothing ended up being wrong under the rocker cover?
 

Stramec

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Hi All
Just for future reference, I fell foul of a 2nd DFI failing in exactly the same way as the first one! I dismissed it as being possible, can't say I even understand the underlying cause. But that is what happened.

Initial DFI failed on one coil.
Bought new DFI.
Same coil still didn't fire.
Went and bought another new DFI from Repco, slapped it in, and worked like a charm. (touch wood)

Thanks to _R_J_K_ & losh1971 for taking the time to offer some help. Was greatly appreciated.
 

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Been there...

A faulty coil can kill the dfi (this happened to me).

You can test the dfi module by removing all the coils and putting a test light across the 2 pins for each coil and cranking the motor.

These days I only use genuine coils and dfi modules if at all possible.

Good to hear you got it sorted and it's always good when the OP updates the thread with a positive outcome/solution :cool:
 
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