Engine Guru's Help Needed

[342Four]

i no this is a skyline forum and all but i need some possible explanations

my wheels is a x3 excel SOHC and im having some probs with it

everytime it is under load - ie going up a hill, it shudders in 3rd and 4th gear (around 50-80km/h)(shuddering like its running on 3 cylinders, barely any acceleration at all uphill even with foot flat on floor)

and sometimes in acceleration from standstill

sometimes the check engine light comes on, sometimes it doesnt

sometimes after driving it will idle really rough - like it is running on 3 cylinders or somefing

my mechanic says that it is a fuel prob as it blows blue smoke out the zorst when it does this (and only when - so its not burning oil - phew)

but being a poor uni student and all i dont want to have to spend buckets loads finding out what it could be

as is ive changed the fuel filter (as it needed to be done anyway), changed spark plug leads(as they were really rooted), swapped the ecu(bugger of a job), checked my spark plugs(they are correctly gaped - although i should get some new ones), injector resistance is the same across all four, ive run it on a tank and a bit of premium, used fuel injector cleaner and all of these to no avail, although it seems to not shuddering as much going up hill now

what could it be?

i should get a diagnostics test done but cant be bothered

and it does need a filter and oil change and a tune

coil packs? spark plugs? injectors?

any helpful help would be appreciated

[qikstagea]

if you are trying to go up hills in a excel, at 50kmh, in 3rd or 4th gear, id say your engine is pinging itself to death. Little engine need higher revs than itll be pulling to make the power to get up hills, bud.

ummm blue smoke IS burning oil... BLACK smoke is burning fuel, so id see a different mechanic to be honest...

PS work on your basic grammar and spelling before you next take it to a workshop. If you come across this unintelligent in front of a mechanic, mate, id say he may be taking you for a ride.

[342Four]

well it needs an oil change so i'll do that and check the smoke then

but it only smokes when it shudders and rough idles - no other time

and maybe i didnt get a proper look at the smoke but it was smoking non the less

and i trust my mechanic so....

i realise it needs revs - what i mean is that it willl start shuddering sometimes in 3rd, sometimes in 4th, and anywhere between 50-80km/h is when ive experienced it

(one situation it will start shuddering just as i change into 3rd going uphill and slowly accelerate until i change into 4th and then leap and jerk its way through 4th up to about 70-80km/h then it is all fine again)

[qikstagea]

ok well try keeping your revs a bit higher, mate. like i said, those engines need more revs than you are giving it. You are making it work too hard, trying to pull that car up a hill. If you are in 4th as you are speeding up to 70-80km, uphill, then you must be changing into forth at about 50...

dude its not a diesel tractor.

try this - 1st gear til about 25-30. 2nd til 45 or so. 3rd til about 60-65. 4th til 80, 5th from there onwards. Less than that, your car just isnt gettin enough weetbix to muscle up hills. Thats whats making it jerk. You need to change your driving style. Itll be pinging itself to destruction, and id say you having been causing damage to working parts by driving it like you do.

Does it smoke when you jerk? (sounds bad, lol) I wouldnt be suprised if the jerking is just you dumping the clutch on it trying to idle up hills, and the smoke is from a different problem altogether.

Those lil engines can take a lot more revs than youd be feeding it (sounds like you are trying to go uphill, in forth, at about 2000rpm....), the reason being because they NEED to.

[342Four]

if ur interested the problem is fixed

one of the wires from the loom had rubbed bare under the dash and was earthing itself out

under load it was too much and it would run on three cylinders - hence the shuddering

here i was replacing injectors, fuel filter, air intake temp sensor blaa blaa blaa

all good now and hopefully my fuel economy goes back up too!!