3.8L v6 Ecotec in vx commodore wont rev out

[Tornack1]

so a few months ago my car broke down on me and it turned out to be a dead coil pack after a bit of searching

however since then I've been unable to rev it over 4500 rpm without it missing and then backfiring out the exhaust when it comes down from that rpm range
i had it good for about a week with having put another DFI module in it however it is now back to doing it with no change after replacing the DFI module again

so far since the problem started I've had the heads off and installed new stem seals, valve springs, valve spring retainers & valve locks
I've also replaced the crank angle sensor, fuel pump, fuel filter, spark plugs with iridium spark plugs, spark plug leads and put injector cleaner into the fuel and done a few hundred k's

I'm wondering if anyone has come across this problem before or heard anything or has any ideas as to what it might be

the motor also has 1.98-1 rockers, cold air intake, bored out throttle body, 12mm plenum spacer, 25mm manifold insulator, 2.5 inch exhaust with extractors, performance coils & a retuned ecu to suit

the valve springs fitted were 105# springs

 

[billythakid]

MAF sensor plugged in properly ?

 

[Tornack1]

yeah MAF plug is firm and a good connection
ive also had the codes read on it and there are no codes logged in the ecu

 

[Bowen]

If it's back firing I would suggest looking into the dfi module, CAS, and cam position sensor, as these are the only things which control ignition timing, I resmember a really really good thread on testing ignition modules (not just the module as uv replaced yours twice but the operation of them) going through issues with bad grounds through bad connection as the dfi grounds itself through the alloy base using an engine ground, and various other things

I think it even went into detail about putting in a dedicated earth straight into the module?

If the teeth on the back of the harmonic balancer are damaged or warped goil have issues too....

 

[theghostoftime1978]

so a few months ago my car broke down on me and it turned out to be a dead coil pack after a bit of searching

however since then I've been unable to rev it over 4500 rpm without it missing and then backfiring out the exhaust when it comes down from that rpm range
i had it good for about a week with having put another DFI module in it however it is now back to doing it with no change after replacing the DFI module again

so far since the problem started I've had the heads off and installed new stem seals, valve springs, valve spring retainers & valve locks
I've also replaced the crank angle sensor, fuel pump, fuel filter, spark plugs with iridium spark plugs, spark plug leads and put injector cleaner into the fuel and done a few hundred k's

I'm wondering if anyone has come across this problem before or heard anything or has any ideas as to what it might be

the motor also has 1.98-1 rockers, cold air intake, bored out throttle body, 12mm plenum spacer, 25mm manifold insulator, 2.5 inch exhaust with extractors, performance coils & a retuned ecu to suit

the valve springs fitted were 105# springs

Hi mate, i have a 99 VT which is having similar issue as you, stalled which at lights, would not start after. i checked engine codes and showed DTC 49 cam/crank signal error. so replaced crank and cam sensors. still coming up with error code 47 18x input missing or grounded. replaced harmonic balancer. swapped my DFI and coils back to my old ones. took it for a drive, gave it a boot and stalled and backfired. changed ignition leads....

someone said to me it could be a blocked cat converter? car has done 285000km and still has original cat. if this is blocking flow would it cause car to stall and possible throw a fault code???

also i have nearly the same mods as you. mace 1.98 rockers, mace 12mm spacer (which i took off due to bonnet not closing properly) 25mm mainfold spacer, mace memcal, lukey 2.5 cat back, bosch fusion spark plugs, bosch motorsport leads, MSD coil packs. Did have mace pod set up, but sold it due to loosing power went back to factory box.

 

[devilly]

have you changed the pcv value ? when its on idles and you remove the dipstick whats it feel like if you put your finger on it ?

check the tightness of the bolts from exhaust to engine,any air leaks at the egr value ?

any more information on what's it's doing ? any noise from exhaust on idles ?

 

[theghostoftime1978]

other than backfiring when i boot it. car will idle fine. just when i drive it for 10 mins it and give it a boot it would start to lose power and stall. Then it wont restart straight away or until i reset the fault code. I have just changed my manifold gasket and cleaned the whole top end of motor to sparkling metal.

 

[devilly]

maybe re-tighten the bolts on manifold gasket vacuum leak at throttle body.

 

[Tornack1]

ok so ive had the harmonic balancer checked and its fine, crank and cam angle sensor have been redone to be certain as well as a new ecu and fuel pressure regulator. have checked for any leaks on exhaust and intake and have found none. any further ideas would be greatly appreciated as im running out of things to try before i strip the harness down to check it

 

[billythakid]

Did you replace all 3 coil packs or just the one that was dead ?