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('04 VZ SV6 5-Auto) Slight miss/hesitation low RPM & medium-high load

Dechlan Tutty

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'04 VZ SV6 - Auto (5 sp.)
Hi everyone,

I've looked through previous posts and can't find a circumstance that lines up exactly with what I'm experiencing, at least in about half an hour of reading.

Anyway, about 2 months ago my car started one time after about 100 km of highway driving and being left for 2 or so hours, was fine for 5 minutes, got to temp and then had a hissy fit and lost all 1 bank (spark, fuel or both, not sure). Anyway, parked it up at home, luckily downhill most the way, opened bonnet and it had fried coil #3 (middle coil on drivers side, pretty sure that #3 Cyl.)

I replaced the coil, called an auto elec, he just replaced a fuse and all was well until the other day. A slight miss/hesitation has returned but only between 1900-2000 revs when the auto box is "locked up" about 90-105 km/h it ends up being. When you roll into the throttle more than say 20-25% it jumps every half second or so like a misfire, but isn't consistently every power stroke. When it unlocks and kicks down a gear, or you chuck it into 4th manually, problem goes away.

I have a cheapo OBD scan tool, enough to read codes and I use Torque app on my phone to see all engine data. The only thing I notice when it happens is the spark timing goes from 18 or so degrees advance to 0, but never throws a code.

The car's done 210,900 km, I changed the oil about 500 k's ago (I do it every 5-6k), and I'm planning on doing the auto's fluid in the next few days. Not sure where to go with diagnosis from here. It's probably due for a set of timing chains soon, but no other signs they might be gone, is this them showing their age or is it something I'm missing?

Thanks for the help in advance, I'll provide more info if you need. Cheers, Dechlan
 

Dechlan Tutty

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'04 VZ SV6 - Auto (5 sp.)
Still having issues. Does anyone have any idea at all?
 

krusing

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2002 VY L67 Calais Sedan, 2012 VE L77 Calais Wagon
Get is scanned with a professional tool,
Possible timing chains,
Check spark plugs, and set them to 1mm gap,
Check ALL the Earth's/Ground connections, as they have 4 on the VZ's.
 

Dechlan Tutty

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Mar 1, 2020
Messages
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Reaction score
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Location
East Gippsland, VIC
Members Ride
'04 VZ SV6 - Auto (5 sp.)
So, the car's fixed now. Turns out it had to do with when the coil pack cooked itself. The head of the spark plug had gunky stuff on it and it wasn't contacting as nice as it could've been, so I replaced all 6 plugs while I was there, even though they were only about 25,000 km's old.

That helped but then threw an injector code. Cleaned all driver's side bank injectors, checked plugs/connectors and cleaned them too.

Mechanic reckons the chains are still in good nick, yet can't give an estimate on how long they'll be.
He checked a couple "easy to get to" grounds and cleaned them a little bit.

Runs like it did before it cooked the coil again.



Now... I'm being pedantic, I know, but there has been this very slight hesitation maybe around the 50 km/h mark when accelerating more than say 40-50% throttle for the past year or so at least, and I can't remember whether it was there when the car was bought or whether it formed later on.

Could it just be a funny motor mount, seeing as the motor purrs now? or is there potential for something else to go now?

Anyway, thanks for the suggestion krusing, you were pretty on the money. Cheers
 
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