vp v6 wagon(LEMON) running rough as guts!!!

[v8supra]

g`day guys....Everytime i even think about going near this car something goes wrong!!Anyway it`s latest trick is to run realy rough almost all the time now,at idle and when driving, it lacks power and sounds very "fluffy" if that makes any sence.Today when i fired it up it ran smooth and perfect but it only lasted about 1 minute then back to being a shakey old pig again.This car recently has had new fuel pump/filter,ignition module, coil packs,plugs,leads and reco injectors.Done a comp test today because i was thinking maybe a crook valve `cause that`s what the engine sounds like but the lowest was 130 and the highest 140 and while that isn`t real flash i figure all is ok inside the engine .After the comp test i fired it up and let it run for about 10 mins and in that time i reckon it went from smooth to rough about 4 times before deciding rough was where it wanted to be.
There are no error codes logged and i`ve checked vaccuum lines etc and it`s got me stuffed!!!
I`m sure this is something simple but i`m out of ideas.

appreciate any help.
cheers.

[Peter89]

well, i run a heavy oil in my vn wagon, seems to make it run smoother. unusually rough could mean poor airflow, check the intake. could also be a result of unstable fuel supply, maybe worth getting the fuel pressure. it seems you have already replaced what i would normally suggest.

[delcowizzid]

can be the coolant sensing circuit in the ecu they make it do things like this too.or the coolant sensor itself or the hose to the map sensor

[aussieghostrider]

100% its inlet manifold gasket ....

same symptoms as you ... misfire at low revs/idle

loses water over time ....

it will get worse and will stall on you .... other symptoms are higher than normal idle and car gets automatic cruise control

I put few bottles cargo stop leak just so I could keep car going ...

Im getting inlet manifold gasket replaced this week ... $300

the gaskets $50 ...

you can damage pistons and your oxygen sensor will corrode and die quicker than usual .. If you look at where the manifold sits on top of engine look around the back and if you see fuel smelling oil then there you have it..

get the inlet manifold gasket replaced and also get a new oxygen sensor and new spark plugs ... I bet your fuel economy will be great then ... and also faster acceleration etc ..

Hard acceleration and high revs are not good for the old inlet manifold gaskets ... I know this because mine died from me overtaking too much

[Alloytec]

give the map sensor (near throttle body) a light tap when running

also check vac hoses to the map sensor , fuel pressure regulator, check vac hose from brake booster to inlet manifold ..

as ghostrider said the inlet manifold gaskets are common to leaking while i havent ever experianced a air leak from one they do leak water across into the oil etc people pannick and assume the head gaskets are gone lol.

[v8supra]

Hose to the map sensor is fine and i tested map sensor according to workshop manual and all was ok...Inlet manifold gasket is something i didn`t think about so i`ll run soapy water around the manifold and see for any bubbles.I`ll try and do this tommorow and let you know how i go.
Thanks guys.

[aussieghostrider]

^^^

the soapy water trick doesnt always show the leak ... because thats the outer seal of the gasket ...

the leak is inside where water jackets are that keep inlet manifold cold and leaks water into cylinders ..

I heard you can put white paper towels twisted up and take out spark plugs when engines warm and putting twisted up paper towels into where spark plug hole is and apparently you will see traces of green on paper towel if you leave in there till engine cools right down ...

just make sure the paper towel is twisted up tight so it will come out easy ... you just need it sittin in there to collect any green coolant ... u want it to back out easy as you dont want that shit stuck in there lol so dont force it in there.

[v8supra]

G`day guys......Just when i think things couldn`t get any worse with this lemon of a car, they do!!!!
Got some soapy water happening to ckeck for manifold leaks,went out to open the bonnet and the left hand bonnet hinge crapped itself and put a large crack in the bottom of the winscreen!!!After i calmed down i started the lemon and proceeded to check for leaks but nothing showed up.It doesn`t use any water and there`s no water in the oil so i`m not so sure this is the problem.I`d hate to replace the gasket and have it still run the same.I`m not sure what i`ll do next.This is a 2 owner car that was looked after and as soon as i took ownership it`s been a nightmare.I`m realy temted right now to drive it into the dam .....Iwill try that paper towl trick ghostrider but not right now `cause if i go out there agian today something else will go wrong and the lemon will take a swim!!!
Thats my rant for the day........
cheers.

[v8supra]

I replaced the bonnet hinge today and after that i was looking at the intake manifold and decided i`d check the botls to see how tight they are.The front one`s were very tight but some of the side`s and back all needed a half a turn.Now i didn`t realy expect that to do much but started the car and it ran as smooth as ever!!!When for a drive for abot 15 minutes and it was nice and smooth and had all it`s power back.I`m not convinced yet that this problem is solved but usually it wouldn`t run smooth for this long.Just as i thought things were all good the check engine light came on.Came up with code 43.Could the knock sensor cause any of the problems or is this a new one???
cheers.