vs v8 misfire\hesitation HELP!!!

[vs_grunta]

OK..... i have read nearly every misfire thread on here over the past 2 weeks and i done everything that everyone has suggested and still no go.

i bought my vs II 5.0ltr calais about 2 months ago. It has:
-yella terra rollers
-100mm throttle body, 100mm pipe to 100mm k and n filter
-ported and polished heads
-custom chip burnt from efi dynamics
-stage 2 shift and 2900 stall

At first it started to miss every once in a while , like once during a trip (30min to an hour). it sort of felt like a crook plug or lead, like an electrical missfire. This miss started to get worse and more frequent, so i took it to a very highly reguarded mechanic in victoria who is supposed to be the best at fixing\tuning\diagnosing 5.0ltr v8 commo's, $250 bucks later he says he is not able to tell me whats wrong with it. he tested :
-fuel pump pressure
-fuel quality
-coil spark
-lead resistance
-spark plug gap
-ignition module
-error codes (only 12)

He also ran the car on the dyno and checked all mixtures and power.he burnt the chip for the car 5 years ago and the dyno run ran right over the run 5 years ago! same power In his opinion he says it feels electrical like a surge or a miss.

I kept on driving the car and the missfire gradualy got worse.
Not being able to get any help i started working on the miss myself. I have done:

-new coil
-new leads
-spray start ya bastard on all vaccume hoses looking for air leak
-wrapped electrical tape on 1\2 the intake k and n filter to change mixture (rich)
which made it run fat, reduced miss. but miss was still there
-pulled of each lead while running to find problem cylinder, all made car labour. all ok
-did a leak down test on each cylinder all ok
- sparyed crc on all electrical components

The other day i took off from the lights reasnobly quickly and it pulled under power then died and now the miss has gotten so bad that it wont rev very well, and the miss is noticeable all the time even on idle. the car wont drive cause it misses very badly under load. Hade to tow the car home.

I dont know what to do now the only things i can think of is a ignition module( but im told that they either are working or not they wont run but break down. Or a crank angle, sense.

any help will be appreciated

[vsv8berlinawag]

I had a similar issue and was told that the iginition module either works or it doesn't. I replaced the leads, rotor button, dizzy cap and coil, but all of this was in vain as the the miss was still there. In the end I managed to get a second hand one from eBay, installed it and the problem immediatley went away. One thing I had that you didn't mention was that my tacho would bounce all over the place when it was missing pretty bad (that went away as well).

[vs_grunta]

Yeah i replaced dzzy cap rotor button 2! i got a ignit mod lined up but dont want to buy it if it the wrong part . . . again!
the thing is my tacho dosnt bounce . thanks for the reply

[brockee]

is it losing power the more u put ya foot down on the pedal???or miss or surging at idle??

[vs_grunta]

missing when you put your foot down. just went down and picked a ignit mod from reapers peformance and changed it over. no joy. by the way reaper is really helpful!!!

[Vt-Brrrlina]

like above mine did the same....
chaged

rotor
dizzy cap
leads
spark plugs
ignition module
coil.


something there fixed a massive misfire..sounded like a drive by shooting bang bang bang....

[vs_grunta]

ok just changed ignit module and spark plugs and was driving very roughly down street, i sropped the car put it in reverse and gave it the grunt and it did not miss once in reverse!!! spun the wheels and drove it up to about 60 k's!! but when i put it in drive it developes a big miss/hesitation when driving foward!!

[brockee]

my vr did the same thing was couple of years ago now i think it was either a crack in the coil+ u can not see it to!!!! or the fuel pumps justd about fxxked does it prime when u go to start it???an also mine ran like a heap off shit an went no where

[vs_grunta]

new coil and fuel pump tested by mechanic. runs great in reverse !! huge miss going foward.

[David Brennan]

mate i had this exact problem with my vr 5ltr it all seemed fuel or electrical then i dropped my exhaust off before the cat converters to see if it was blocked and this was the problem. try that if the car runs fine then time for new cats

[vs_grunta]

but it runs fine in reverse. just foward it misses badly under load, maybe a vac hose on the gearbox that only runs drive???

[VrWagz1]

You dont have a cas as such. Its called a hall effects sensor and its located in the dizzy itself. You may need to change your whole dizzy. I have heard of a few dizzys having troubles with the hall sensor.
When you drive forward your motor twists to the drivers side, have a look down there somwhere maybe somthing (like a wire loom, sensor) is maybe getting rubbed through and touching somthing.

At a pinch change the ecu. I beleive v8 - v6 all the same, just need to put your memcal chip in it. But if it was me my next move would be a dizzy swap out as the hall sensor does all the timing for the injector firing and spark n stuff. Speaking of injectors, how are they and their wiring??

[vs_grunta]

Yeah the dizzy was my next point of interest, have changed cap and rotor too, but not the rest of dizzy, have looked \ jacked the car to try and find a cable pulling rubbed through, but i cant see anyting. i have run the car and pulled\wiggled a my loom sensors to try and make it miss worse but no good. the thing thats jamming me up is it does it in d,1,2 but not in reverse, thats what all igniition parts are not void cause it would do it all the time,
\
It has to be loom\earth sensor that works only in drive, gearbox????!!!! i guess

[vs_grunta]

oh and new injectors, sorry,

[vs_grunta]

finally fixed my problem!!!!!!
the coil pack on my 5.0ltr sits pretty close to my firewall, and what was happening was when i took off the engine would tourque to the right and make the coil pack hit the fire wall and earth!!! but it would do it intermittedly!!!! cause of the paint on the firewall was slowly wearing off. I had to bend the original bracket you get with a bosch coil pack to make it clear the wal completly!!
Thanks all for you help!

[Vee-ard]

finally fixed my problem!!!!!!
the coil pack on my 5.0ltr sits pretty close to my firewall, and what was happening was when i took off the engine would tourque to the right and make the coil pack hit the fire wall and earth!!! but it would do it intermittedly!!!! cause of the paint on the firewall was slowly wearing off. I had to bend the original bracket you get with a bosch coil pack to make it clear the wal completly!!
Thanks all for you help!

Excellent, good to hear mate.

[simmons001]

Wow, that's a weird one. Will keep that in mind.

Congrats on the fix