VN idling ruff, backfiring, loss of power, guzzling fuel

[VN_Pretz]

hi guys,

i own a VN V6 5spd

i recently bought an SV3800 memcal off of ebay (item #230223561795)

not sure if this caused the problem but it only started happening after chip had been installed.

i can start the car, drive for around 10minutes running as per usual, then once the car has warmed up, engine light comes on, i start backfiring and crackling alot, also have trouble idling, gets very rough and idles around 500rpm, it's chewing through petrol like theres no tomoro, and i'm also losing power.

i have since removed the performance chip and replaced it with the original, but problem still occurs.

the thing that confuses me is that it funs fine until the engine light turns on ? ? but once the engine light is on, it stays on until i turn it off and let it cool down.

i changed my oxygen sensor thinking that was the problem, but it didnt fix anything.

plugs and leads are fine.

i've tripped the computer and the 'check engine light' just stays on. i tried resetting the ECU by disconnecting battery, and i tripped the ECU again and got code 12, then when i run the car for a bit, the engine light comes back on, and we start having problems, then i trip the ECU and the light just stays on and doesnt flash a code.

sorry for the novel, but i'm just trying to be specific.

any help would be greatly appreciated

thanks heaps

[beefcream]

coilpacks or crank angle sensor, search them to and see if you can match any symptoms

[Emackulation]

Check for error codes! Search the forums for "checking error codes" or something similar for the how to.

EDIT. I fail at reading lol

[88GreenVN]

Start with a CAS.

[greenfoam]

Since there is no error code, Im going to put my bet on a dodgy connection inside the ecu on one of the lines that goes from the eprom to the guts of the ecu and once the ecu gets warm it's expanding and dropping the connection (so try swaping to another ecu)

[h0Ld3n`VN]

i have the same problems 500revz, loss of power, backfiring(once one night) but fuel economy is great?.. hmm ever since my ecu drowned in water(dont ask how) it played up like this
so foamys right its the eCU!

[johnnythaboy]

hmm ever since my ecu drowned in water(dont ask how)

dont be like that mate. do tell :P

[FXST01]

hi guys,

i own a VN V6 5spd

i recently bought an SV3800 memcal off of ebay (item #230223561795)

not sure if this caused the problem but it only started happening after chip had been installed.

i can start the car, drive for around 10minutes running as per usual, then once the car has warmed up, engine light comes on, i start backfiring and crackling alot, also have trouble idling, gets very rough and idles around 500rpm, it's chewing through petrol like theres no tomoro, and i'm also losing power.

i have since removed the performance chip and replaced it with the original, but problem still occurs.

the thing that confuses me is that it funs fine until the engine light turns on ? ? but once the engine light is on, it stays on until i turn it off and let it cool down.

i changed my oxygen sensor thinking that was the problem, but it didnt fix anything.

plugs and leads are fine.

i've tripped the computer and the 'check engine light' just stays on. i tried resetting the ECU by disconnecting battery, and i tripped the ECU again and got code 12, then when i run the car for a bit, the engine light comes back on, and we start having problems, then i trip the ECU and the light just stays on and doesnt flash a code.

sorry for the novel, but i'm just trying to be specific.

any help would be greatly appreciated

thanks heaps

Try putting your old chip back in and see if it does it, sounds like your new chip to me

[VN_Pretz]

thanks alot guys, the old chip is back in, but as foamy said it must be the computer

i'm changing my thermostat, crank angle sensor and possibly coil pack this weekend, so will see how it goes

[h0Ld3n`VN]

if you change just the ecu n if thats what the problem wouldnt it be easier??? borrow a ecu off a mate???

[VN_Pretz]

well guys, i changed the ECU

same problem

still getting no fault code when warm and system clear when cooled down

i changed DFI module, Coil Pack, Plugs, Leads, MAF sensor

it's really frustrating, i also took it to kmart tyre and auto on friday with the original ECU, they couldnt get into it, hopefully they can get into this comp

i also noticed it kicks in once engine fan activates.....


thanks guys

[vnv8driver]

splash some cold water behind the harmonic balancer (crank angle sensor) and see if that temporarily cures the problem, if it does then the cas is overheating giving the wrong reading to the ecu, thus the firing sequence will be out of whack.

could also be coilpack

[Glen_P]

If it is the CAS do a search on ebay, I picked up a brand new one for $28 in sydney works perfectly!

[VN_Pretz]

update....

i poured water on the CAS, no deal, still playin tricks and didnt help at all

but i did notice something, once the engine light comes on, the harmonic balancer seemed to be off balance, it was wobbling slightly, like it had speed wobbles

my old man thinks its the harmonic balancer giving the CAS a false reading

what do you guys think

[vnv8driver]

grab the harmonic and try to move it side to side, if there is even the slightest of movement, the rubber mount is stuffed, this can cause the harmonic grooves to smash into the cas and destroy it, usually instantly though but can chip and knock it out of place, although if it would be doing it all the time not just when warmed up..

theres other options that could explain your problem like the coils and dfi module

[VN_Pretz]

i tried to move the H/B but didnt seem to do it for me

i've changed coil pack and DFI module and still no deal (the DFI module is under the coil pack right?) i've also tried pouring cold water on them

it's really annoying

[vn calais manual]

you poured water on your coilpacks and module.............

[VN_Pretz]

yeah, was told to pour water on it to see if it fixed the problem

[vnv8driver]

on the crank angle sensor......

[vn calais manual]

yeah, was told to pour water on it to see if it fixed the problem

on the crank angle sensor.

[vnv8driver]

i've tripped the computer and the 'check engine light' just stays on. i tried resetting the ECU by disconnecting battery, and i tripped the ECU again and got code 12, then when i run the car for a bit, the engine light comes back on, and we start having problems, then i trip the ECU and the light just stays on and doesnt flash a code.

i just had another good read of your first post (which i usually dont do lol) the ecu light staying on when your checking for codes in a bit weird.... but otherwise still sounds like the cas, one of the coils or dfi module. splashing water usually cures it for a short period but some dont respond at all.

get a video and ill be able to tell you if the motor is misfiring or not.

[vn calais manual]

and if it wasnt missifiring before u poured water onto the dfi and coilpacks. it may just be now

[Bz Kn33z]

I had a simular problem, turned out it was lack of fuel pressure and i replaced the fuel pump and sender and it fixed its self, might be something to check but yeah, really sounds like the CAS keep trying to check for codes might work one time. good luck

[VN_Pretz]

hi guys,

the latest

i changed the Harmonic Balancer and Crank Angle Sensor last night with my dad

the crank angle sensor looked fine, but i thought i'd change it seeing as i had one and i had access to it

but..

i am still experiencing this problem

i am going to take it to a mechanics on monday and get them to at least tell me what it is

depending on the job i may get them to fix it

[VN_Pretz]

hey guys

this morning i noticed, the engine fan was on when i first started the car and had let the car cool overnight, does this mean it's got to do with the cooling system

maybe temperature sensor, could this be faulty and tell the car to run rough so i dont drive it or something?