Uh oh....thoughts

[Paul in NZ]

last few days when starting the 535 have a definte miss which goes away almost instantly.
LAst oil service aI also changed the plugs and checked leads dizzie and rotor alllooked clean sound and dry.
Last night as soon as i got home i released the expansion tank cap to release all pressure(hoses are definetly firm,not rock hard)
Replaced cap this morning,no miss upon start up.....I am thinking head gasket,but oil alos still loooks clean and coolant is also clean.250 000 ks as far as i know no previouis overheating or head work.

[myles]

last few days when starting the 535 have a definte miss which goes away almost instantly.
LAst oil service aI also changed the plugs and checked leads dizzie and rotor alllooked clean sound and dry.
Last night as soon as i got home i released the expansion tank cap to release all pressure(hoses are definetly firm,not rock hard)
Replaced cap this morning,no miss upon start up.....I am thinking head gasket,but oil alos still loooks clean and coolant is also clean.250 000 ks as far as i know no previouis overheating or head work.


I don't think you need to jump to that conclusion just yet. Unless you have oil in the water, water in the oil, or your residual cooling system pressure remains high after the car has sat overnight. Or of course you have a volcano errupting from the expansion tank cap when the engine is running (I mean an erruption, not a steady trickle)

[Ferret]

I don't think you need to jump to that conclusion just yet. Unless you have oil in the water, water in the oil, or your residual cooling system pressure remains high after the car has sat overnight. Or of course you have a volcano errupting from the expansion tank cap when the engine is running (I mean an erruption, not a steady trickly)

I agree, usually when an M30 HG goes, you really know about it, it'll spray water everywhere violently.

Pull your plugs for peace of mind and see if one's shiny clean :)

You've probably got a minor air leak somewhere/fuel pump/fuel pressure regulator needs looking at

[Paul in NZ]

I agree, usually when an M30 HG goes, you really know about it, it'll spray water everywhere violently.

Pull your plugs for peace of mind and see if one's shiny clean :)

You've probably got a minor air leak somewhere/fuel pump/fuel pressure regulator needs looking at

plugs are very new,ie one week old,would fuel pump or fpr give the same start up symptoms as i describe.As soon as i rev it a bit shes as smooth as she has ever been and settles into the normal slightly iregular M30 idle

[Ross]

could be an injector leaking down giving that cyl a bit of extra fuel to burn off

[Paul in NZ]

could be an injector leaking down giving that cyl a bit of extra fuel to burn off

injector place to clean? or new injectors?

[Ferret]

injector place to clean? or new injectors?

How's your valve clearances?

[Paul in NZ]

How's your valve clearances?

dunno..i only do the basic stuff....what influence would they have?

[Ferret]

dunno..i only do the basic stuff....what influence would they have?

If they've drifted out of spec over time, the engine will be more prone to having misfires induced. When was the last time they were done?

[Ross]

There are numerous places online that do it for ~$20 usd each. They will sonic clean, flow test and replace the filter and o-rings. If they test fine, once clean are good as new.

[Rus]

Check all possible sources of vacuum leaks. At idle the engine is producing high vacuum and is most susceptible to being affected by vacuum leaks. check your intake system rubber boots, vacuum hoses (these become hard over time and can crack). The 535 really only has two small vacuum hoses. one leads to the valve cover ventilation hose (center of cover, 90 degree connector sits inside rubber pipe) and the other hooks up to the fuel pressure regulator. The brake booster has a large vacuum hose connected to the intake manifold. Inspect these for obvious cracks and tears. Replace as necessary. Also have a look at the o-ring on the dip stick and the oil filler cap seal. If those leak, you'll have a small but possibly noticeable engine issue. To see what a vacuum leak does to the M30, pull of the oil cap while the engine is running. See if that sounds like your misfire. HTH

[Zeuk in Oz]

Possiblity of faulty spark plug ? Given that they are new.
Vacuum leak ?
Other electrical lead - crank position sensor, cam sensor, etc etc ...?
Fuel pump relay ?
Fuel pump ?


First things that come to mind without knowing anything specific about the M30 engine.

Not to mention not being a mechanic.

I would probably suggest waiting a little while, whilst monitoring all the vitals, as I am sure it will get worse and then perhaps lead to an easier diagnosis.

Time to get that 540i / M5 ????? :D

[Paul in NZ]

Possiblity of faulty spark plug ? Given that they are new.
Vacuum leak ?
Other electrical lead - crank position sensor, cam sensor, etc etc ...?
Fuel pump relay ?
Fuel pump ?


First things that come to mind without knowing anything specific about the M30 engine.

Not to mention not being a mechanic.

I would probably suggest waiting a little while, whilst monitoring all the vitals, as I am sure it will get worse and then perhaps lead to an easier diagnosis.

Time to get that 540i / M5 ????? :D

have been looking for a nice e34 540 or e 39 540 manual for quite a while,very small market.Surprisingly E39 M5s are now coming into the affordable range....to buy anyway!

[Paul in NZ]

thanks for the help guys...i do get the car serciced regularly,and keep the coolant fresh etc.Just to reiterate,the miss goes away almost straight away,only when first starting up after a full day or o/nite...although it didnt do it this morning.