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Rough idle after new injectors?

Kokentoe

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Hey guys,

I've got a VZ v6 ute. I changed the fuel injectors the other day as well as the fuel filter. Car started up and ran fine, but it now had a rough idle which was not present before. I initially thought that perhaps there was a vacuum leak so I checked the manifold gasket and all the hoses and couldn't find anything. I then swapped back to the existing injectors I had and the rough idle is gone. Would anyone know why this is? I would have thought that using brand new injectors would make the car idle even smoother but this isn't the case. Any help is appreciated.

Cheers.
 

Immortality

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What was the reason for the injector change? Did you fit the same specification injectors? Checked for a pinched 'O' ring when fitting the new injectors?
 

Kokentoe

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No reason in particular, I just had a spare set lying around so I thought I'd use them. I did inspect the o-rings and they seemed to be intact. The injectors themselves appear virtually the same apart from the tip which is slightly wider, but fits without an issue. As for the specification, it states:

"Injectors are direct replacement of the Bosch black plastic type with EV6 plug. Injectors will fit any Bosch fuel rail and can be used in any engine running a Bosch fuel rail.
Applications - Holden Commodore VZ, VZ Ute, VZ 1Ton LEO / LY7 3.6L 6 cylinders 2004-2006 Early Pre Euro 3".

So compatibility should be fine. It seems unlikely, but could it be that the ecu needs time to get used to the new injectors? The car has been tuned if that makes a difference. Other than that, I've got absolutely no idea.
 

ari666

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The car has been tuned if that makes a difference.

car has been tuned for the injectors that are currently working

not tuned for the ones you put in it...


pretty much answers itself doesnt it? are they at least the same colour with the same part number printed on the side? by saying "tip which is slightly wider" would suggest that theyre different injectors.
 

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Do they flow the same lbs as the ones you took out?
 

Kokentoe

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So in other words if your car has been tuned and you change the injectors, you must get the very exact same type? The description for the new injectors said it was compatible with my vehicle.

I don't know if they flow the same but the car was driving the same. The only difference was the rough idle. I didn't notice any loss in power.

Some photos. Old injector = blue o-ring.
 

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Immortality

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Looks like a cheap copy to me.

The original has the injector part number moulded in the box on the side, the new one doesn't.
 

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Well if the ecu is expecting 42lb injectors and you then fit 60lb injectors (just making up numbers here) then your fuel maps are going to be waaaaaaaaaaaay off and the car will run like a bag of crap.
 

diysv6

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Don't want to hijack the thread, but I am now curious.

Where do the O2 sensors fit in this new tune "fuel mapping"?

Are the O2 sensors set to different air fuel mixture calibrations depending on MAF IAT and throttle position RPM etc etc?

Could it be that one of the replacement injectors is faulty and this is throwing things off tune?
 
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