vt missfire, tried the usual things

[motard_mike]

ok i have a vt wagon with 220k kms on it. the car gets used for towing 1000kg+ ski boat every weekend and has developed a miss at 1800-2500 rpm when under load. if i shift down manually and get the revs up it pulls like a champion but that doesnt help much when trying to get up a boat ramp and the car wont even move. I have had the ignition system tested and it came back fine. First i was told it had a leaky inlet manifold gasket and loose injector seals replaced all that. since then I have been told to replace the coil packs... did that $150 same problem. CAS was next $80 same problem, Ignition module $170 same problem. now the mechanic wants to do the injectors and im sick of throwing money at it. is there any way i can test and find teh exact problem before i give up and get a au falcon wagon?

[accentstencil]

How old are your plugs and leads?

[motard_mike]

leads are 6 months old max, plugs not sure to be honnest. if aftermarket are ok i guess thats a cheap next thing to try.

[motard_mike]

genuine $20 for 6.... couldnt beleave it! ill put them in tonight and see if that helps.

[BowTie]

If no luck with that^

then do a dry/wet compression test.

I have blown head gaskets between 1 & 3 with no external signs other than a severe miss.

[motard_mike]

head gaskets also done, that was a seperate issue so didnt mention it. also done new radiator and cooling system inc thermostat.......

[holdenvtman1123]

i use iridium plugs and get 100k km a hit out of them. they cost 20 bucks each

[Ozzie]

i use iridium plugs and get 100k km a hit out of them. they cost 20 bucks each

well arent you a sucker for advertisment.

why buy high heat plugs unless ur v6 is stroked runnin meth or avgas?
you dont pay more because they last longer.

[crisp5.0]

ozzie i just replaced my dizzyin my vt 5.0l now i have a slight miss or choke or somethiong under accaleration any ideas its only happened since new dizzy

[codeunknown]

loss of grunt from a dizzy...can be due to a few things...a leaking coil...or a coil failing under load..
check that ...

also a bad earth...bad earth on cars cause issues like car computer issues....battery charging....and anything that requires a earth base feed...so check and clean the earth points..add extra straps if you like...
and clean the battery terminal...

check the high tension leads and plug leads for ""air pressure gap"" this caused by shoving the cap on and it traps air inside...as the car gets it so does it and hot air inside lifts the plug leads on and off contact...
how to fix? easy...when you fit the new leads on lift with a small flat screw driver...and allow air to escape while you push on...once on remove the screw driver...
known to be a issue with brand new fitted leads and or dizzy cap..


and this misss that is new... could it be due to splippage in the transmission or clutch..given you pull --tow allot ? perhaps if a auto trans when was the last time the auto trans filter was renewed and new oil given to it..in its hard life of towing...
and perhaps the kick down needs adjustment as well...and in general a auto trans service..
if the car is manual...the same rule applies to clutch ?

[motard_mike]

well guys i put in the new GM plugs.... and bam she runs perfect! the old plugs even looked good and where NGK items. any way thanks for the advice and i still cant beleave that the brand of plugs made that much differance!

[mickymodge4]

hey mate is your car on dual fuel????

[mickymodge4]

if so which gas plugs part numbers were they????