Cold Start BackFiring - Holden Vr

[Vr wagz]

i have a cold start problem when i drive the car when cold the car consistently backfires until it is warm. also when the car is warm and i change gear and ease off the clutch the car will backfire. Also i have recently replace the spark plugs and over the weeks since i changed them it has been getting worse. i never had a drama like this with the old spark plugs i was wondering if this had anything to do with the problem or is it just a coincidence. I was wondering if anyone could shed some light on the problem if they have had it before. any help would be greatful.

just for reference my ecu is a haltec - so i cant read error numbers.

Thanks ~

 

[aussie4life]

Sounds like maybe a timing issue and the unburnt fuel is causing the backfiring. I might be wrong but worth a shot. Im sure other people will be able to give you more ideas

 

[pjdm1980]

Did you do leads at the same time?



PJDM1980

 

[Jxfwsf]

as above, leads?
air filter? fuel filter? Fuel pressure reg? Leaking injector? CAS? DFI?

possible to get your hands on a stock ecu and run it for a bit and see if it logs any errors?

 

[Vr wagz]

leads are new installed same time as the spark plugs, if i put octane boaster in my fuel and the problem is still there would that rule out bad fuel. what do you mean by timing issue.

 

[drewVHSS]

check to make sure all the coils are firing properly.
i've had a coil intermittantly fail and when it did fire every so often I'd get a backfire, car chugged running on 4 cylinders and with a backfire it'd come to life for a second or two and back to chugging on 4 cylinders.

Does this fit with what your's is doing?

 

[Vr wagz]

yes certainly does but ive always thought it did that because i have a stage 3 crow cam which is lumpy.

but as i said recently it has started to backfire ALOT, for example i was reversing out of my garage on a coldstart and as soon as i put my foot on the accelerator pedal it just KEPT backfiring till i took my foot off the accelerator.