AWD drivers please look

[RichiesTrucking]

i know nothing about mechanics so diagnosing is difficult to say the least, especially with what i thought was a very intermittant problem but possibly not? i want to throw an idea in and see if you guys think it makes sense or not

initial problem: driving along and the car gets a little jolt. this happens very infrequently and with no obvious trigger. it can be pulling away, it can be running at a steady 30MPH. no reason for it or predictable time or situation
the jolt also seems to come from different places on the car. sometimes at the front, sometimes at the back but it can go for several days without it happening which is substantial mileage ie well over 200 miles

last night i arrived at work and reversed into a space. then i stopped and turned the ignition off at which point the car started shaking while the turbo timer counted down. txts and facebook messages all pointed by 3 people to a problem with misfiring or plugs and leads. assuming this is correct, is it possible that an uneven engine is producing lumps of power which due to a front LSD and rear open diff, could cause what i percieved to be a mechanical fault making the car jolt? my logic being that if it is sending out uneven power then the distribution of that through the transmission could also be uneven which could cause a jolt. again, i know nothing about mechanics so i may be completely wrong but i dont know

 

[thexav]

Is it caused at high RPM, is there a pattern at all here as it sounds pretty random to me. A miss fire tends to happen more than infrequently and is a loss of power. Do any fault codes show up on a diagnostic read?

 

[RichiesTrucking]

the fault was originally thought to be a front transfer box issue so it was replaced with an EVO 5 RS part (i got very lucky) but not only is the problem still there but it doesnt seem to come from any direction. i know with a knackered rear diff that it is easy to tell whether its front or back with a diff but this is not specific to front or back and there is no pattern or trigger. last monday i was tootling along at 30MPH then nothing for a week. the next time i was pulling away from lights and i dont pull away hard. i have been driving the car gently for a while now. no one seems to have any idea what it is. i am using logic and thinking if the engine has a misfire then can that be transferred through the transmission so what feels like a transmission or suspension fault may be a surge split front and rear plus both front wheels meaning different levels of power are reaching the wheels causing a jolt. i may be making no sense though but i am not qualified to know either way

 

[SLEEPER]

Is your system permanent 4wd or variable awd as in the ratio of power front to back is controlled .

 

[Yugguy]

Misfire sounds like to me. When my coil packs went on both banks of the v6 it made the engine run very uneven, shook the car.

 

[RichiesTrucking]

its a permanent 4WD with a 50/50 split front/rear although there is debate on a 40/60 front/rear split under hard acceleration. it now has an EVO V RS front transfer box with a helical LSD diff and an open rear diff but the problem was there with the old transfer box with open diff. the transfer box was wrongly diagnosed which is why it now has a better one

 

[obi_waynne]

What fuel are you using? Try a tank of shell vpower (or another 99 octane fuel) and see if the problem is related to the knock sensor.

Are you running a custom map?

 

[SLEEPER]

It is either a fixed split or it isnt and if not it must have a control system

In that case it could be a fault in that control system . Could be the ecu or a lot of things

This certainly has been known to occur on stageas where the wrong fluid level does really funny things to the awd system