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

VT Surge/Misfire only while in gear

BadSeed

New Member
Joined
Jun 13, 2006
Messages
29
Reaction score
0
Points
1
Members Ride
VT V6 Berlina Wagon
Hello all,

Just had my spark plug leads and some other work done on the car (engine mounts, suspension etc) the car is now misfiring/surging (which it wasnt doing prior to service). The plugs weren't changed as they had only been done 2 months prior.

This only occurs while the car is in gear (ie: can sit and rev it fine in neutral, but if I put it into gear sitting stationary and rev to around 1800-2000rpm foot on brake, it misfires).

Have been told that its possible fuel injectors (have just changed fuel pump which was dirty) so they may need a clean, but why would it rev fine in neutral if it was these?

Or could be DFI Module/Coil packs, apparently coil packs tested okay but mechanic didnt have a spare DFI Module to try.

The only other thing I notice is that one of the spark plug leads seems to be not so snug/tight fit as the others? As in doesn't get pushed in as far.

Any suggestions what would cause it to misfire only while in gear? (Currently in a remote town, so trying out parts from wreckers is a bit hard :( )

Cheers
 

BadSeed

New Member
Joined
Jun 13, 2006
Messages
29
Reaction score
0
Points
1
Members Ride
VT V6 Berlina Wagon
Noone? :(

Need my car drive back away to work on Tuesday =/
 

Brett_jjj

Well-Known Member
Joined
Oct 16, 2009
Messages
6,805
Reaction score
83
Points
48
Location
Tamworth NSW
Members Ride
vs commodore
Ive seen this same problem before caused from faulty ignition coils. They misfire when the engine is put under and sort of load, but will still run ok when the engine is idling or reved up in neutral. Ive seen these coils do this even when they've showed up as being ok when tested with a multimeter. Its best ( if possible) to replace all ignition coils at the same time, as these coils slowly lose their performance over time until they reach a point where they start to fail when theyre put under load. Stay away from aftermarket coils, sure, theyre cheaper than genuine coils, but most Ive tried are inferior quality, which effects the fuel economy and also effects how good the car starts and runs etc, and they dont last as long as genuine ones.
 

immortality

Can't live without smoky bacon!
Staff member
Joined
Apr 15, 2006
Messages
15,677
Reaction score
3,804
Points
113
Location
Sth Auck, NZ
Members Ride
HSV VS Senator, VX s2 Calais S/C
IF you have a problem just after you have worked on the car, go over the things that have recently been done.

You mentioned a loose spark plug lead, could very well cause your issues. If you still have the old leads, give those a try and see what happens.

Was the fuel filter changed after stuffing around with the pump? When was the fuel filter last changed? Seeing as the fuel system has been disturbed it could have send a whole lot of crap into the fuel filter causing issues.

Brett is correct about the ignition coils, however seeing as they seemed fine before the service it's likely that they are still fine after the service unless maybe you did a engine wash and moisture got into something.

Revving an engine is neutral is completely different to been in gear and under load which taxes the ignition system a lot harder but if the fuel system is playing up it will also miss.
 

BadSeed

New Member
Joined
Jun 13, 2006
Messages
29
Reaction score
0
Points
1
Members Ride
VT V6 Berlina Wagon
The lead is a wierd one I suppose, I have tried second hand ones (that made no difference/made it worse) and since being remote no others around here to try. without ordering in a new set (I had driven the car 300km to servicer centre for the service and took the vehicle on drive home and noticed the misfiring etc).

It seems they have cleaned all around the DFI/coil pack I guess changing the engine mounts they degreased everything.

The fuel filter was changed after the issue became apparent, by the communities local mechanic, and said it was rather dirty etc, so could be a bunch of crap gone through into the injectors to cause it possible, so have tried running injector cleaner and getting it onto premium but still no better.

So basically unless someone at my work (mine site) has leads/coils I can test with I will have to start ordering in parts to try resolve it, or drive it the 300km back to the main mechanic to let them test it. :(
 

ashbox

back in black
Joined
Apr 17, 2007
Messages
1,302
Reaction score
5
Points
0
Location
The Car
Members Ride
something black
me, personally, if it started happening after the main mech touched it, i'd be taking it back to them to solve
 

BadSeed

New Member
Joined
Jun 13, 2006
Messages
29
Reaction score
0
Points
1
Members Ride
VT V6 Berlina Wagon
me, personally, if it started happening after the main mech touched it, i'd be taking it back to them to solve
Would love to, but I live 300+km away and return to work tomorrow, had it serviced Thursday and drove home that night and noticed it happening and getting worse etc.

They have said it could be injectors dirty and don't believe it was anything they have touched etc, as I had spoken to them about it possibly misfiring at cruising speed, but no where near as bad as this. So they might of taken that as it was already happening, but they did say after the service it was occuring.
 

BadSeed

New Member
Joined
Jun 13, 2006
Messages
29
Reaction score
0
Points
1
Members Ride
VT V6 Berlina Wagon
In case anyone is wondering, turned out to be spark plug gap, was told that on the old leads not as much resistance? So the problem became a lot more apparent with new leads. The gap was closed in (from 1.8ish) to around 1.3mm to compensate for potential wear of coils.

Now runs fine!
 
Top