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Multicylinder Misfire

Bardy-II

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My 06 VZ is misfiring on cylinders 2, 4 and 6. As the car starts up you can hear slight popping and misfiring, it then settles and is only really noticeable under acceleration. Was hoping to find some solid reasoning as to why? I've seen other threads but a lot of them go straight to timing chains or coil packs, and my timing chain has already been done?

Done the spark plugs but I don't wanna splash out on the coils as all of them being on the same bank it seems unlikely to be individual coils? Any advice would be helpful!

Whilst driving my vac hose came off, and the problem started after this, so I'm thinking maybe the cat on the relevant side has been fucked from an incorrect fuel ratio, but would that cause a misfire if the cat was fried? That's the question I'd love to know the answer to! I'm also assuming 2,4 and 6 are on the passenger side?

If anyone can help that would be great, thanks!
 

_R_J_K_

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Well, your problem is occuring on an entire bank and I doubt very much that 3 coil packs would die at once. Dead cat is also unlikely, they're not that fragile.

Which vacuum hose are you talking about?
 

Bardy-II

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Well, your problem is occuring on an entire bank and I doubt very much that 3 coil packs would die at once. Dead cat is also unlikely, they're not that fragile.

Which vacuum hose are you talking about?
Yeah I thought the same thing, I'm gonna swap the plugs to the other bank to make sure but it seems so unlikely. Again, got a TPS code but that would surely cause problems all round not just on the one bank?

The vacuum hose for the AC vents with the white valve? It came off whilst driving, that's why I thought maybe cat would be the problem because it was problem running to rich/lean for a while which may have done it it?
 

_R_J_K_

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Would probably look at your TPS issue first, how did you determine they were missing on just those cylinders?
 

Bardy-II

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So the TPS connector lock has been snapped off so it doesn't lock properly but I would have thought a TPS problem would affect all cylinders not just one bank? Obviously I'm going to get a lock for it regardless

I scanned it and it came up with P0300 random misfire then the following 3 codes were for 2,4 and 6 misfiring?
 

_R_J_K_

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Yeah okay. Chase up the TPS issue first and then reset the ECU and see if the problem continues. It might just be that the misfire is across all cylinders but is just more pronounced or crosses the error threshold on just one bank, possibly because of manifold design (if you look at the intake runners they split into two chambers, one for each bank) or some other tiny detail.
 

Bardy-II

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Ooh oksy c
Yeah okay. Chase up the TPS issue first and then reset the ECU and see if the problem continues. It might just be that the misfire is across all cylinders but is just more pronounced or crosses the error threshold on just one bank, possibly because of manifold design (if you look at the intake runners they split into two chambers, one for each bank) or some other tiny detail.
Oh okay cool so to reset the ECU how would I do that? Disconnect the battery or the PCM plug or?
 

_R_J_K_

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Disconnect battery for a few minutes.
 

Bardy-II

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Yeah so I've done that, to no avail, I have switched a couple of the plugs up, but also ineffective. I've used the scan tool to check the O2 sensors and it's interesting as I think possibly both of them on that bank side have failed possibly causing the misfire?

Getting a reading of 0.000kOhms on Sensor Heater B1-S2 and on Sensor Heater B2-S2 so both on Bank 2 but I'm at a loss! I might just have to replace them and see what happens?

Also getting a open loop reading for fuel bank 2 so possibly going to just do the O2 sensors and hope for the best?

Your opinion would help man thanks for everything so far!
 

_R_J_K_

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Did you fix your TPS issue before you did all that?

O2 sensors might be worth a shot, but if they're anything like the Ecotecs they just make you use more fuel if they've failed (although it running rich could also cause a miss fire). Should replace them anyway if they're not working.

Were the plugs on that side sooty and black or covered in petrol?
 
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