Hesitation - Possible Causes

[e34.535i.sport]

When the capatin was revving it up last night I was looking under the bonnet for anything unusual - eveything looked fine but after a few revs there was a serious smell of fuel...

Could the popping/hesitation and smell be injector related?

[anonymous1]

Hi,

I have noticed over the last few weeks that I have a hesitation on accel between the lower end of revs. Generally happens at about 1-2.5rpm. When this happens I seem to be getting what sounds like a misfire (popping type) noise from the engine. The noise only happens once and then the engine seems to pick up fine. (Although by this point I have already been beaten from the line by the clapped out Rover Metro with 26 grinning passengers next to me!)

I have replaced the rocker cover gaskets and this hasn't made any change. Replaced all spark plugs as thought they may have been damaged by previous oil leak from the gaskets.

Wondering if this could be a vacuum leak or what the other possible causes could be? I don't know if the previous owner ever had the fuel pump changed, although I haven't heard any whining noises coming from the rear.

If there's any extra info you need me to provide let me know.

Thanks in advance.

[finalanarchy]

My mums car used to have a bit of hesitation of the line, turned out to be something like sparkpulg master lead, can't remember exactly what he called it.
Hope that helps.

[filip00]

try sparkplugs first if they're old, then if it still continues go test injectors

[whiskychaser]

Hi,

I have noticed over the last few weeks that I have a hesitation on accel between the lower end of revs. Generally happens at about 1-2.5rpm. When this happens I seem to be getting what sounds like a misfire (popping type) noise from the engine. The noise only happens once and then the engine seems to pick up fine. (Although by this point I have already been beaten from the line by the clapped out Rover Metro with 26 grinning passengers next to me!)

I have replaced the rocker cover gaskets and this hasn't made any change. Replaced all spark plugs as thought they may have been damaged by previous oil leak from the gaskets.

Wondering if this could be a vacuum leak or what the other possible causes could be? I don't know if the previous owner ever had the fuel pump changed, although I haven't heard any whining noises coming from the rear.

If there's any extra info you need me to provide let me know.

Thanks in advance.

You can mask all sorts of ills by revving it a bit more. What's the idle like? If its lumpy you might be looking at an intake leak. Check it by removing the oil filler cap-the idle speed should change a bit. But dont get too excited. It might not if your filler cap isnt sealing in the first place.

[anonymous1]

Cheers for the input.

At the moment I have already changed the spark plugs a couple of weeks back and while this seems to have made the car run smoother, it hasn't got rid of the hesitation as I hoped it would.

The idle is smooth and does not rumble at all, so thinking this may mean it's not a vacuum leak. Or can one be caused by a bad intake manifold gasket as accel is applied?

Had a look at the engine yesterday and seems the petrol smell is coming from the injector area. (If I haven't been running the engine for long, I can sometimes smell it faintly when I walk around the front of the vehicle - which might explain the smack heads queuing up to sniff my engine whenever I pull up at lights! ) A couple of the injectors look pretty old, but they weren't noisy. Is it possible if I had a leaky one, that it would only have an affect when the engine was at low revs.

Whisky - Your right on the masking with higher revs, if I keep the revs around 1.5-2K as I start off and take each gear fairly high, then I don't get the issue. Just concerned in case it's something that may get worse with time.

Cheers again.

[anonymous1]

Hi,

I was considering changing the leads to the sparks in case it is bad wiring that has been causing my issue. I have spoken to the Stealer and they have advised I can't buy individual HT leads, but rather I need a whole new harness and that will be £700 approx + VAT.

Just wondering if anyone knows if this is right or if I can replace/buy individual leads?

Also wondering if I can smell petrol from the area of the injectors if they can be repaired or would I need to replace the suspect one on confirming if it's leaky?

Cheers in advance.

[e34.535i.sport]

Just wondering if anyone knows if this is right or if I can replace/buy individual leads?

Found this bro...

http://www.bimmernut.com/forum/showt...ight=m50+coils

[e34.535i.sport]

Even better...

http://www.bimmernut.com/forum/showt...ight=m50+coils

[anonymous1]

Hi,

I have been looking in to replacing the ignition coils and this seems to be a pretty expensive if I can't work out exactly which one is causing the issue. (If it is this)

I took one of the ignition coils off before and noted that the top of the spark seemed to have a glazed look. Checked the rubber spark plug socket on the bottom of the coil and this appears to have oil in it as well. (I presume this has got there from when the rocker cover was leaking into the wells) Now I'm wondering if the oil could have gotten on the contact point in the spark plug socket? If this was the case, would it potentially cause my low rev hesitation/misfire?

I have checked with BM and they sell this part separately for £8 inc VAT, so not too bad if I do have to replace them. Or would it be OK if I just cleaned them instead (although this could be tricky - cotton buds may be the order of the day) with brake cleaner for example or anything else you can suggest?

I am referring to #3 in this:
http://www.realoem.com/bmw/showparts...25&hg=12&fg=05

Another thing I am not sure if could be the cause is this hose:


It seems to be loose, but not sure what the hose does and if it matters how tightly fixed in place it is?

Thanks in advance.