2005 Monaro VXR - lumpy idle/misfire
Discussion
I have a monaro vxr with lpg conversion. it has about 101,000 miles and has a lumpy idle/misfire. Its as if its making the sound; bummm........bum...bum.......bummm on idle and gradually becomes unnoticable as I increase revs.
The lumpiness is less noticable from outside but you can feel it though the seat and it vibrates the car quite alot sometimes.
I replaced the ht leads but no luck with that.
Something I thought may be of significance is that the the injector pipes for the LPG were not tapped into the intake manifold AT ALL when i got the car meaning there were loads of vacuum leaks. However, this is fixed now and as far as i can tell there are no air leaks in the manifold, but the car is still misfiring!
Any thoughts would be appreciated
The lumpiness is less noticable from outside but you can feel it though the seat and it vibrates the car quite alot sometimes.
I replaced the ht leads but no luck with that.
Something I thought may be of significance is that the the injector pipes for the LPG were not tapped into the intake manifold AT ALL when i got the car meaning there were loads of vacuum leaks. However, this is fixed now and as far as i can tell there are no air leaks in the manifold, but the car is still misfiring!
Any thoughts would be appreciated
Sounds like the pvc hose to me. It’s pretty common in Oz that they split and the symptoms are similar to what you described, rough idle and ok when accelerating.
I’m pretty sure it’s this little guy
https://www.ebay.com.au/itm/Genuine-Holden-New-PCV...
And that it goes here:
https://images.app.goo.gl/M1T9434bNBps2gyu8
I’m pretty sure it’s this little guy
https://www.ebay.com.au/itm/Genuine-Holden-New-PCV...
And that it goes here:
https://images.app.goo.gl/M1T9434bNBps2gyu8
Plugs?
Possibly an inlet manifold gasket leaking?
Or map sensor?
Where abouts are you? you’ve not got an area in your profile. If you can’t find the problem yourself You need to get it to someone who has a reader with Holden specific diagnostics. Before you do that, go on the Facebook page as lots of the old members from here went over to there, go to the HSV & Holden Owners UK page there’s lots of experienced people there.
Possibly an inlet manifold gasket leaking?
Or map sensor?
Where abouts are you? you’ve not got an area in your profile. If you can’t find the problem yourself You need to get it to someone who has a reader with Holden specific diagnostics. Before you do that, go on the Facebook page as lots of the old members from here went over to there, go to the HSV & Holden Owners UK page there’s lots of experienced people there.
Worth a bit of a nose around engine ground and battery ground too. I had a bit of a misfire which was sorted by tidying up my battery ground (I've relocated it to in the boot) and the grounds on the cylinder heads (front left and back right as you look from the front of the car).
Not sure where you're based, I have a spare coilpack that you could rotate through from 1 to 8 and see if it tidies it up.
If the miss at idle is consistent and audible and vacuum leaks are ruled out, you could try unplugging each coil pack 1 at a time and see if the misfire gets worse or stays the same. If it stays the same with one of them unplugged you've at least narrowed it down to a specific cylinder
Not sure where you're based, I have a spare coilpack that you could rotate through from 1 to 8 and see if it tidies it up.
If the miss at idle is consistent and audible and vacuum leaks are ruled out, you could try unplugging each coil pack 1 at a time and see if the misfire gets worse or stays the same. If it stays the same with one of them unplugged you've at least narrowed it down to a specific cylinder
Had a look at the pvc hose and its fine, no splits. I used throttle body cleaner everywhere around manifold and the that goes from the cylindrical part of the intake but no luck. Anybody know anywhere else i could be looking for leaks?
I cleaned out the throttle body too but no luck. I couldnt access the IAC because it has unusual alan key screw heads.
The lumpy idle is with petrol and lpg. Although the car actually runs marginally better on lpg.
Sturdy HSV thanks for the tip, Ill try unplugging one coil at a time and see what happens, or what doesnt happen :P Im based in Liverpool btw.
I cleaned out the throttle body too but no luck. I couldnt access the IAC because it has unusual alan key screw heads.
The lumpy idle is with petrol and lpg. Although the car actually runs marginally better on lpg.
Sturdy HSV thanks for the tip, Ill try unplugging one coil at a time and see what happens, or what doesnt happen :P Im based in Liverpool btw.
I think i found the problem. I unplugged the maf sensor to see if there was any difference. The car started but idle was way worse meaning the maf is working. However between the bad idling it occasionally ran really smooth with no misfiring.
Think ill get some maf cleaner and see what that does.
Think ill get some maf cleaner and see what that does.
Is it modified apart from the LPG system?
I don't know much about LPG, so I don't know if they play with the actual factory tune on the car or whether it's just sort of piggybacked on, but running on petrol with the MAF unplugged it should still idle largely fine, it's got plenty of data to work from (aside from Intake Air Temperature) that it shouldn't be particularly rough
Certainly mine's been unplugged for tuning purposes perviously and it made little difference.
The MAF is just a few resistors suspended in the air flow behind a metal grill, it's not an overly complicated device so unsure how much the cleaning would help, but seems unlikely to do much harm trying.
Sorry I can't be of much more use
I don't know much about LPG, so I don't know if they play with the actual factory tune on the car or whether it's just sort of piggybacked on, but running on petrol with the MAF unplugged it should still idle largely fine, it's got plenty of data to work from (aside from Intake Air Temperature) that it shouldn't be particularly rough
Certainly mine's been unplugged for tuning purposes perviously and it made little difference.
The MAF is just a few resistors suspended in the air flow behind a metal grill, it's not an overly complicated device so unsure how much the cleaning would help, but seems unlikely to do much harm trying.
Sorry I can't be of much more use
MW94 said:
Had a look at the pvc hose and its fine, no splits. I used throttle body cleaner everywhere around manifold and the that goes from the cylindrical part of the intake but no luck. Anybody know anywhere else i could be looking for leaks?
I cleaned out the throttle body too but no luck. I couldnt access the IAC because it has unusual alan key screw heads.
The lumpy idle is with petrol and lpg. Although the car actually runs marginally better on lpg.
Sturdy HSV thanks for the tip, Ill try unplugging one coil at a time and see what happens, or what doesnt happen :P Im based in Liverpool btw.
Unplugging one coil at a time will allow raw fuel into your cats, assuming you have them which will do them no favours.I cleaned out the throttle body too but no luck. I couldnt access the IAC because it has unusual alan key screw heads.
The lumpy idle is with petrol and lpg. Although the car actually runs marginally better on lpg.
Sturdy HSV thanks for the tip, Ill try unplugging one coil at a time and see what happens, or what doesnt happen :P Im based in Liverpool btw.
If you wish to kill a cylinder for diagnostic purposes here, unplug an injector.
Although viewing info from each lambda sensor will also give info as to whether one side is unhappy or not.
I hope it wasn't converted by Mark.
Anyway the maf is your likely culprit, MAF cleaner wont do it any good but give it a whirl anyway. You are far better off by wiping the adapted learning tables, then unplug the maf and see how it runs as no down the stft has been so f
ked that your long term trims are making it run like a ginger asthmatic.
To reset the adapted trims (as you will be an LS1 not that horrid E40) then look for the BCM fuse, pull that, turn ignition on until all sorts of alarms and the dash goes a bit mental, turn ignition off, replace the fuse then retry your mafless test.
Of course it could be a coil or a plug, in fact if you don't know when they were last done why not replace the plugs anyway, nothing too cold as you aren't running the 1/4 mile a run at a time. At this age, the maf will be about as accurate as a labour party fiscal manifesto.
Anyway the maf is your likely culprit, MAF cleaner wont do it any good but give it a whirl anyway. You are far better off by wiping the adapted learning tables, then unplug the maf and see how it runs as no down the stft has been so f
ked that your long term trims are making it run like a ginger asthmatic.To reset the adapted trims (as you will be an LS1 not that horrid E40) then look for the BCM fuse, pull that, turn ignition on until all sorts of alarms and the dash goes a bit mental, turn ignition off, replace the fuse then retry your mafless test.
Of course it could be a coil or a plug, in fact if you don't know when they were last done why not replace the plugs anyway, nothing too cold as you aren't running the 1/4 mile a run at a time. At this age, the maf will be about as accurate as a labour party fiscal manifesto.
PCM not bcm fuse
Pull fuse
Turn on ignition to position 1
Wait, think it alerts to failed abs or something, turn off, plug fuse in, start.
Warning initially the idle could be bksed run in petrol not lpg mode.
http://www.ls1.com.au/forum/archive/index.php/t-10...
Pull fuse
Turn on ignition to position 1
Wait, think it alerts to failed abs or something, turn off, plug fuse in, start.
Warning initially the idle could be b
ksed run in petrol not lpg mode. http://www.ls1.com.au/forum/archive/index.php/t-10...
I know this was ages ago but after all this time im pretty certain what the issue is.
I used a fog machine for air leaks and there was a split in the induction pipe which fastens to the throttle body. Ive just sealed it up with some jb weld and waiting for it to set.
Im pretty sure this will cure it!
I used a fog machine for air leaks and there was a split in the induction pipe which fastens to the throttle body. Ive just sealed it up with some jb weld and waiting for it to set.
Im pretty sure this will cure it!
MW94 said:
I know this was ages ago but after all this time im pretty certain what the issue is.
I used a fog machine for air leaks and there was a split in the induction pipe which fastens to the throttle body. Ive just sealed it up with some jb weld and waiting for it to set.
Im pretty sure this will cure it!
That's good news, hopefully fixed?I used a fog machine for air leaks and there was a split in the induction pipe which fastens to the throttle body. Ive just sealed it up with some jb weld and waiting for it to set.
Im pretty sure this will cure it!
Not fixed, I did another fog test as I forgot to open the throttle body the first time. I couldnt find any fog coming out anywhere in the engine bay.
I noticed spits of engine oil in the air intake duct that clamps to the throttle body after my brother revved it highly. Its as if the car violently jolts when revved cold.
The engine oil is also a little overfilled but didnt think much about it. Could that be whats causing the violent hesitation and shudders when revving the engine?
I noticed spits of engine oil in the air intake duct that clamps to the throttle body after my brother revved it highly. Its as if the car violently jolts when revved cold.
The engine oil is also a little overfilled but didnt think much about it. Could that be whats causing the violent hesitation and shudders when revving the engine?
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