Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

VS MISS-FIRE UNDER LOAD, POWER LOSS AT OPERATING TEMP.

Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
Hi I'm a bit stuck with this problem.
I have a bad miss-fire at about 2000 to 2600 RPM. Worse when hot. Probably needs a top end job, (slight oil in coolant, oil clean) but I can't afford that at the moment.
Worse under load, seems to go away over 3000 RPM, but I don't want to have to rev that much.;)
Manual V6, new fuel pump, new injectors, throttle body cleaned. (Fuel return line in tank has no clamp, as I couldn't get the fitting off to replace that one)
Coils seem OK.
I am thinking plugs or fuel, or CAS, or temp sensor, air sensor, but it runs fine at idle (bit of high idle though, then settles).
Also starts missing after cornering, which I think points to fuel?
Fuel filter done a few 100k ago, but I suspect it might have picked up some dirt from the pump change.
No error codes. (was thinking of getting ALDL cable, but no codes with old paper clip)
 

_R_J_K_

Well-Known Member
Joined
Dec 20, 2008
Messages
6,723
Reaction score
1,856
Points
113
Members Ride
Zenki S14
Done any other basics like plugs? I've had a similar issue on one of my other cars fixed with new leads.

CAS generally works or it doesn't, no in between. Temps sensor makes it drink petrol. Other common ones are coils and DFI module.
 
Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
Done any other basics like plugs? I've had a similar issue on one of my other cars fixed with new leads.

CAS generally works or it doesn't, no in between. Temps sensor makes it drink petrol. Other common ones are coils and DFI module.
Yeah done the DFI and coils not too long ago.
I am going to check and replace the plugs, leads are new (ish).
I've done CSA before, and agree it shouldn't be that.
Had thought in would miss all the time if it was the plugs, but they might be breaking down under heat/load?
 

Immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
22,480
Reaction score
19,936
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX Calais II L67
Pull the plugs and check the gaps. If over 1.5mm either close up the gaps (if the electrode and earth straps aren't to badly worn) or replace.
 
Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
Pull the plugs and check the gaps. If over 1.5mm either close up the gaps (if the electrode and earth straps aren't to badly worn) or replace.
Yeah, I will do. I hope It's that simple.
Also have a strange symptom, when I remove the fuel pump fuse, (to depressurise) the starter won't turn over. I remove the fuel relay and it will.
Figure that one out?
 
Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
Done any other basics like plugs? I've had a similar issue on one of my other cars fixed with new leads.

CAS generally works or it doesn't, no in between. Temps sensor makes it drink petrol. Other common ones are coils and DFI module.
Fuel consumption is normal, just the annoying miss when hot under load.
 

Immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
22,480
Reaction score
19,936
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX Calais II L67
Yeah, I will do. I hope It's that simple.
Also have a strange symptom, when I remove the fuel pump fuse, (to depressurise) the starter won't turn over. I remove the fuel relay and it will.
Figure that one out?

You should always pull the relay for the fuel pump as it's a 2 way relay and it will power the fuel pump once the engine gets oil pressure.
 
Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
You should always pull the relay for the fuel pump as it's a 2 way relay and it will power the fuel pump once the engine gets oil pressure.
OK. I'm sure the manual said pull the fuse.
I'll use the relay from now on, but the starter should still work with the fuel pump fuse out, right?
 

HSVBMW

Member
Joined
Jul 12, 2017
Messages
37
Reaction score
15
Points
8
Location
South Australia
Members Ride
vh vn vt
Sounds like swirl pot,return line has def popped off if no clamp. If car has 1/4 of a tank of fuel or less fill above half say 3/4 and see if runs fine. If it does thats what it is. Not only under acceleration and cornering will the car starve for fuel but the pump will over heat and cut out and eventually die young. Swirl pot must be full at all times no matter amount of fuel in tank to keep supply and pump cool.
 
Joined
Aug 31, 2012
Messages
47
Reaction score
2
Points
8
Location
Australia
Members Ride
VS Executive wagon, VE wagon
OK, pulled the plugs and checked the resistance of the leads, (and the new injectors just in case.)
Leads checked out fine.
The old bosh plugs were sparking yellow, with gaps of about 1.7mm
Cleaned (and set to 1.1 mm the plugs) the MAFS and it went like a dream for the test drive.
However after we stopped for a swim (about 1/2 an hour) it was missing continuously on the way home.
New plugs go in tomorrow.
Dose anyone out there know if the MAFS will work better after a clean if it is on the way out? Or do they just give up like the CAS.
I hit some bumps on the test, so not discounting the idea that the return line might be off, but it ran sweet on the test.
Thanks for all the help.
 
Top