There's a rumble in the jungle...

[e34.535i.sport]

Hey guys, haven't posted with a problem for a while: I'll try to keep it brief!

I've got an intermittent rumble when idling, coupled with what *feels* like a misfire - occasionally. Most of the time the car is running superbly and idling pretty (well for the 30 anyway), but now and again when sitting at lights I can feel the engine suddenly rumble as though it's struggling in a wierd way and then return to normal... It's over in a few seconds. Also it's been doing a similar thing at low speeds sporadically. Injectors are new and sound, ignition wires I've checked and vacuum leak is highly unlikely as I've checked thoroughly! The car seems to run much smoother when it has more that 1/4 tank of petrol which I'm assuming is not the norm?

I have my suspicions (fuel related!) but thought I'd seek more knowledgable opions before wading in and possibly wasting my time!

I don't know if this is related but most days on the way home from work I drive along the same road and get to a place where I am just moving along in third gear and I always let off the throttle to let the car slow naturally for a particularly awkward speed bump. Wehn I do this the car bucks as though it's going too slow but it's not... I put the clutch in and let it back out and it runs perfectly thereafter. Definitely not clutch related as this is new(ish), seems more like it's being starved.

What do we think?

[Ferret]

How're your engine and gearbox mounts?
Gearbox input shaft?
Big ends?

I've got several rumbles on my new slag car at the moment, need to get em sorted out.

[e34.535i.sport]

How're your engine and gearbox mounts?
Gearbox input shaft?
Big ends?

I've got several rumbles on my new slag car at the moment, need to get em sorted out.

Engine and gearbox mounts both new... Thought about those myself initially but it's not that kind of rumble and the fact it's so intermittent makes me think it must be something to do with either electrics or fuel? ???

LOL what's your new 'slag' like then Andy?! :D

[whiskychaser]

Does it sound anything like this?:
http://www.youtube.com/watch?v=QJPOwu7TbmM

If not maybe check your fuel pressure?

[e34.535i.sport]

Does it sound anything like this?:
http://www.youtube.com/watch?v=QJPOwu7TbmM

If not maybe check your fuel pressure?

LOL maybe a little?! :D In fact, I think the car sounds better!

I was thinking about fuel pressure too... So on an *unrelated* note, what you up to this weekend Colin?! :p :)

[whiskychaser]

LOL maybe a little?! :D In fact, I think the car sounds better!

I was thinking about fuel pressure too... So on an *unrelated* note, what you up to this weekend Colin?! :p :)
I know what the fuel pressure should be on the M50 but not on the M30. You look that up and I will find the pressure gauge:D

[e34.535i.sport]

I know what the fuel pressure should be on the M50 but not on the M30. You look that up and I will find the pressure gauge:D

Hahaha will do and thank you very much! :D

[Ferret]

LOL what's your new 'slag' like then Andy?! :D

Well after picking up the e39 540, I realised I'd gone in the opposite direction away from an involved drive. Dont get me wrong, the 540 is an awesome car and makes for good commuting... but just doesnt have the insanity I was looking for.

Enter a wildcard and someone minus a license selling it cheap :) the new slag's an STi (no slags with an sti jokes please, we're British!)

It's practically uninsurable, rattles, suspension crashes, gearbox whines like a straight cut rally car, bits fall off and I'm at the mercy of endless chav jokes, but by god when it moves all is forgiven:
http://i11.photobucket.com/albums/a190/Ferret101/DSCF0234-1.jpg

It's a bit of a toy, it's being kept as a second car to run around and tinker with! Yeah I know the scooby impreza is a chav car, but generally speaking chavs cant afford the STi model which will flatten almost anything else out there :D

[whiskychaser]

My reg ends 'WRX' if you are interested;):D

[e34.535i.sport]

Well, with many thanks to my old pal Whiskychaser we're *pretty sure* we tracked down my intermittent issue... The fact it was by accident is trivial. :D

We checked fuel pressure and vacuum... Both of which came up fine. When we fired her up afterwards however we noticed some light smoke coming from the rear of the engine near plug #6.

Turned out to be oil leaking down from the valve cover gasket as one of the nuts had backed off a fair bit... The oil was then burning off down below by the spark plug itself - possibly causing an the odd, annoying, sporadic misfire! Wipe it down, tightened up the valve cover nut as it was pretty loose and it seems to have sorted itself out luckily enough.

Overall a fairly productive day! If nothing else i learnt a lot lol and jumpered my first relay! :p