97 VT Misfiring under load............

[gobes32]

Hi guys, sorry my first post has to be a problem but I found this forum while googling my problem with my VT.

I have a problem with my VT, when it's warm it misfires something shocking. It even backfired today, TWICE..... I have changed leads and plugs, and even swapped coil packs with my mates car and nothing....... The problem did become not as severe when I changed plugs and leads but as soon as i put my boot in it, it runs like a dog. Cleaned the fuel filter out too, but am pretty sure that was never the prob anyway. It idles fun and takes off like a cut snake when it's cold, but as soon as it gets to operating temperate, it just bogs down and misfires constantly. Any help is much appreciated.

[gobes32]

Please guys, even a stab in the dark is appreciated at this stage. I am going to try and have Holden put it in diagnostic mode but am told sometimes even that doesn't find the problem?

[batty_123]

my car doing exactly the same...

done plugs n leads checked BRIEFLY coil packs still unsure about them... but in the end i found out that my trac control cud be doin it so i got it on a machine and it came up with a fault code and so i had to get a new abs and trac control ecu... but it still hasnt fixed the problem wat a waste of money

so im not sure man im lookin for the same answer as u are..

[commsirac]

Please guys, even a stab in the dark is appreciated at this stage. I am going to try and have Holden put it in diagnostic mode but am told sometimes even that doesn't find the problem?

Very much a stab in the dark.
The backfire was through the exhaust? not the airbox.

Given you have changed the plugs and leads, perhaps we can rule them out.
Could be the coil packs failing when you put the boot in.....firing voltage goes up(needs to go up) when the amount of fuel in the cylinder increases. If the coil isnt able to do this then there will be no spark and unburnt fuel goes down the exhaust...when you eventually do get some spark...combusts the fuel in the exhaust....backfire.
The other possibility is that it is running far too rich when you put the boot in and the coil is having trouble igniting it with the same result of unburnt fuel ending up in the exhaust, this could be due to a failed oxygen sensor which will have everything run rich if no signal(someone please correct me if Im wrong here)

So check coils and mixture.

[jazza15]

Blocked injectors? Get some injector cleaner and see if that solves the problem. A symptom of blocked injectors is what you described.

[pablo]

Well!...I would have thought that if the injectors were blocked, this would have shown up as a problem when cold as well!

[gobes32]

If I drive normal then you would not notice it, but any sudden or hard acceleration and it just bogs down and wants to bloody stall on me. I changed the coil pack before I did the plugs and leads, hoping to save money and diagnose it early, I am almost thinking I should swap them over again now I have changed everything. If it was the crank angle sensor then the car would stall at idle? The car has never stalled and only does this garbage when it is at operating temp.

[sandbar1000]

have another look at the plugs, and or leads?? just coz there new, dosnt mean there good...once bitten, twice shy.

had the same problem once, took me 2 weeks to find out that 2 new plugs were stuffed..

davo...

[chargedvx6]

Didn't do the plugs up too tight by any chance? They don't take too kindly to over torquing and can crack easily. Also the fuel pump relay may be on the dodge. For only $12 I'd try replacing that. It's the one closest to the drivers side strut tower, on the outer side of the relay box in the engine bay from memory.

[Scottie666]

hi, i'm having the same problem. well i own a 1997 vt commodore 3.8 litre done 292,000 it chuggs at certain revs and now has a noise coming from the internal, i replaced the plugs and i have put new ignition leads on and it is running like a shitter, only under load. once it starts to pick up it runs perfect but then once i flatten it it splutters and then stops doing it, any suggestions. there is no water in the oil or vice verser so it can't be getting into the plugs to do this. i'm stumped, any suggestions would be great

[holden123]

hi i had the same problem it came down to fuel pump when under hard acceleration back fired run, like shit.

[Scottie666]

it isn't back firing though. i ud=sed that e10 shit fuel for a bit and now have gone back to 95 and put an injector cleaner through it. only seems to do it when it is hot.

[Scottie666]

just checked the ohms on the coil packs and number 5&2 wasn't reading anything the rest were 6.4ohms then i let it run for 5 mins and &2 were reading the same. you guys reckon it's the coil pack?

[Scottie666]

Hi guys, sorry my first post has to be a problem but I found this forum while googling my problem with my VT.

I have a problem with my VT, when it's warm it misfires something shocking. It even backfired today, TWICE..... I have changed leads and plugs, and even swapped coil packs with my mates car and nothing....... The problem did become not as severe when I changed plugs and leads but as soon as i put my boot in it, it runs like a dog. Cleaned the fuel filter out too, but am pretty sure that was never the prob anyway. It idles fun and takes off like a cut snake when it's cold, but as soon as it gets to operating temperate, it just bogs down and misfires constantly. Any help is much appreciated.

I had the same prob yestersday mate, test the ohms on your coil packs, you will need a multimeter to do this but that is how i found my problem, number 5&2 wasn't reading right so i replaced it and now it is sweet again. get a multi metere and use this diagram
Primary resistance: 0.3 -1.5 ohms.
Secondary resistance: 5-7 k/ohms
http://forums.justcommodores.com.au/...cks.jpg:dance:

[brendon87w]

Hey mate, a mate of mine had the same problem with his VX, i changed the DFI module off my stacked VS and the problem was solved, got to an auto elecy and have it tested

[wetwork65]

Same problem on my VT supercharged - spluttered under load. After weeks of checking everything else, checked the plug gaps and found them too wide. I had not changed them out of the packet (NGKs). Were at 1.6 mm.
Closed them to 1.3mm then no problems all ran sweet.

[greenacc]

sounds like coil to me. Have you checked error codes at all ? a big stab in the dark could be a temp sensor ? maybe the sensor is reading cold all the time so its running rich when it warms up ?

[fitz_vt]

this problem happened to me, i had failed oxygen sensors (they were giving off very low (too lean) so the car was giving extra fuel,) got that fixed, same problem then replaced all the coil packs and leads and spark plugs after that had no problem, i found that i had collapsed coils that were only working when you didn't put your foot down they couldn't work on a higher voltage.
Hope this helps for you

[pac23]

i had a similar problem it was the vacuum hose that runs from the throttle body under the inlet manifold and plugs in at the back of the motor. might be worth having a look if thats fallen out..