3.8l VT hesitation / misfire under light load when warm

[Reuben Campbell]

so sprayed brake cleaner around anything i could get to - No changes that i could find, but i wasn't expecting anything as its idling fine.

Slow ,controlled acceleration everything seems to be fine.
Only when you give it a foot-full does it do its miss thing.

rechecked the coils - they seem to be fine.

Could be an injector, but then if it was failing, then it should be missing all the time, especially at high revs, which they do not.

Going to glue up the plenum to the runners this morning - just have to do some window repairs on the house first...

Glued up the plenum to runners face with No3 (non-hardening) aviation gasket glue - no change. - man that shiz is messy.

its still doing the drop in revs at idle every so often. I'm still suspecting a vacuum leak somewhere, but I'm running out of things to check. All the hose seem intact, and plugging into the ports. I've replaced the hose from the intake to the throttle body as that had cracked, but no change.

Could a intermittent sticking lifter be the cause?
This time of year, it almost never does it as the oil is already warm. During last winter, it would stick for about 60 seconds, then free up fine.

Ill see if I can pick up a Throttle position sensor today and fit that.

Ill also order an injector rebuild kit online - as it seems all the local stores cant/wont stock them in the state, so its going to take a week anyways.

 

[Lex]

Glued up the plenum to runners face with No3 (non-hardening) aviation gasket glue - no change. - man that shiz is messy.

its still doing the drop in revs at idle every so often. I'm still suspecting a vacuum leak somewhere, but I'm running out of things to check. All the hose seem intact, and plugging into the ports. I've replaced the hose from the intake to the throttle body as that had cracked, but no change.

Could a intermittent sticking lifter be the cause?
This time of year, it almost never does it as the oil is already warm. During last winter, it would stick for about 60 seconds, then free up fine.

Ill see if I can pick up a Throttle position sensor today and fit that.

Ill also order an injector rebuild kit online - as it seems all the local stores cant/wont stock them in the state, so its going to take a week anyways.

You know how to error code check by putting a paper clip in the diagnostic port, or a scanner?
I've been wondering if you are getting error codes for the iac?

 

[Reuben Campbell]

You know how to error code check by putting a paper clip in the diagnostic port, or a scanner?
I've been wondering if you are getting error codes for the iac?

I haven't done it before - but have heard of this.
Would this give me different codes that a odb2 reader.

I use a laptop and the software from Envious Customs.
Advanced Engine Diagnostics / Software on Elm St

I dont get any error codes from this.

Im about to go down and buy a Throttle position sensor.
If they have a Idle air control sensor, ill just buy that as well to be sure.

 

[Lex]

I use a laptop and the software from Envious Customs.
Advanced Engine Diagnostics / Software on Elm St

If not getting any error codes, l don't think l'd worry about ( iac) it?

 

[Reuben Campbell]

If not getting any error codes, l don't think l'd worry about ( iac) it?

Well it all seems a moot point.
No parts (TPS, IAC or Injector service kits) available in Perth according to Repco, Auto One and Autopro.

Ive placed an order (TPS and injector kit) and will just drive it in the mean time. Expect to get the parts in the next 3-5 days.

Once fitted, ill update if there is any change.

 

[V6025]

PresWell it all seems a moot point.
No parts (TPS, IAC or Injector service kits) available in Perth according to Repco, Auto One and Autopro.

Ive placed an order (TPS and injector kit) and will just drive it in the mean time. Expect to get the parts in the next 3-5 days.

Once fitted, ill update if there is any change.

Hey Reuben, did you fix your problem?
Haven't seen an update yet.
Have you also replaced the pressure regulator valve?

 

[Reuben Campbell]

Thanks for getting back.
I havent been able to do any work for the last week - been working.
Have a couple of RDOs now till christmas.

Pulled the injectors this morning and 'serviced' them. (new o-rings, filter baskets, pintle caps) and ran brake cleaner through them whilst pulsing the injectors for 30 seconds each.
Spray patterns looked ok to me.

The car is running better i think, but still missing and carrying on. Its an improvment, but not yet resolved.

I have a box of sensors here ready to install, however I am now on standby with my local fire brigade as there is an uncontrolled bushfire nearby.

TPS and IAC next - easy to get to
Cam and crank sensors next
Then coils and DPI plate

ill update if I have any success

thanks

 

[V6025]

Thanks for getting back.
I havent been able to do any work for the last week - been working.
Have a couple of RDOs now till christmas.

Pulled the injectors this morning and 'serviced' them. (new o-rings, filter baskets, pintle caps) and ran brake cleaner through them whilst pulsing the injectors for 30 seconds each.
Spray patterns looked ok to me.

The car is running better i think, but still missing and carrying on. Its an improvment, but not yet resolved.

I have a box of sensors here ready to install, however I am now on standby with my local fire brigade as there is an uncontrolled bushfire nearby.

TPS and IAC next - easy to get to
Cam and crank sensors next
Then coils and DPI plate

ill update if I have any success

thanks

Cool, ok mate will be waiting for that.
Iv'e had the same problem for some time. Mine being a Ecotec V6 VT.
But exact same problem to the letter.
Costing a fortune the way Holden have gone about engine design.
(A parts Cannon nightmare) All I have to do is replace the fuel rail, as that FPR Valve. ("is a bastard to get out") lol.
Anyhow if it works? I'll give a bit of a write up and let the community on here know what iv'e done, what worked,and what didn't. Stay safe with them fires mate. "Their a Bastard too".

 

[Kyle_au]

Thanks for getting back.
I havent been able to do any work for the last week - been working.
Have a couple of RDOs now till christmas.

Pulled the injectors this morning and 'serviced' them. (new o-rings, filter baskets, pintle caps) and ran brake cleaner through them whilst pulsing the injectors for 30 seconds each.
Spray patterns looked ok to me.

The car is running better i think, but still missing and carrying on. Its an improvment, but not yet resolved.

I have a box of sensors here ready to install, however I am now on standby with my local fire brigade as there is an uncontrolled bushfire nearby.

TPS and IAC next - easy to get to
Cam and crank sensors next
Then coils and DPI plate

ill update if I have any success

thanks

I’m also now following this thread with the same issue apart from having zero issues with idling. I don’t get any drop in revs etc. As soon as I apply throttle it starts carrying on and even backfiring.
I’m lucky enough to be good mates with my mechanic, so we completed a bunch of work on it at his workshop (rocker cover gaskets, valley cover gaskets, fuel filter, pads and rotors and a general service), he then took it for a road test. 20 minutes the car was fine, bedding the brakes in and all that. On his way back pulling away from the lights, this symptom appeared out of nowhere.. he’s a busy man, hence why I’m here now trying to find answers on this forum to save him diagnosing for hours

I’ve done the CAS though which is a bastard, the standard tool that mounts in the 3 holes didn’t work as the lugs were too small, and an owner before me looks to have had a go at it and ruined the balancer. Ended up having to take the radiator out to be able to fit a hydraulic puller around it. This all didn’t resolve this issue..
I’ve thrown new plugs at it, my next thing to do is coils and leads, but by the sounds of it this won’t do much. I’ll post updates here so hopefully we can help each other!

 

[Reuben Campbell]

After I got back from the fire today, I had a few hours, so as we all know, jobs don't get done by sitting around - so to the shed..

Replaced the Throttle position sensor - no change
Replaced the Idle air control - no change
replaced the cam angle sensor - no change

Pulled the crank bolt out to change the crank angle sensor, only to realize that I don't have a tool to pull the pulley.
So put the bolt back on, only to be unable to tighten it up properly.
I don't have a torque wrench that goes to the 325nm required (mine only goes to 150nm)

Even if I did, I can't hold the pulley tight enough to stop it turning.

I've tried to use a ratchet strap down to the k-frame - no luck
i pushed my car under my hoist arm, and tried both a strap and my serpentine belt wrapped around the pulley twice with enough tension that I was lifting the car up. - it still turns when tightening.

I'm on call for the fires tonight, and on shift for tomorrows graveyard shift.
Hopefully its tight enough, but if it spins off, that will give me the answer I spose.
It throws the balancer and snaps the crank - new engine at that point, or maybe the car to the wrecker.

How on earth do you hold that balancer tight enough to put enough force to tighten that bolt?
I'm going to Perth tomorrow so I can pick up the balancer removal tool and anything else special I need.


Was doing some reading last night - my lifters are sticky/noisy , particularly when cold. Normally it clears up once warm.

Is this something that could cause my issue? Would a playing up lifter cause this? ie not opening or closing the valve properly?
Would this throw an error to the computer?
Is there any value in one of those lift treatments in a bottle? (I've always been very skeptical of 'mechanic-in-a-bottle' products.

thanks