350i occasionally cuts out under heavy acceleratio

[ScumbagAdie]

My 1986 350i occasionally cuts out whilst accelerating. Once stopped restarting the engine works fine but the slightish touch on the throttle causes it to cut out again (electric I'm sure).

After a while one can start it and be off again with no problems.

This last happened many years ago and was never diagnosed. It suddenly happened again recently for no apparent reason.

Any ideas?

[dickymint]

Welcome to the forum
Sticking my wet finger in the air here!! check your earths first. The ignition amplifier (black box of trickery on the distributor) can break down and give this type of intermitant fault especially on a hot engine.
Hold tight and I'm sure others on here will give advice.
PS see you at BBWF 2005?

[wedg1e]

Could be the dreaded dry joints in the ECU. That would explain the intermittency.
I presume during the original diagnostic session they tried stuff like the throttle pot; if that goes 'rough' then you normally find it's the idle/ off-idle that's worst though, full welly is usually OK
Could be one of several things, including the ignition as suggested. How about stuck vacuum advance on the distributor?

[jmorgan]

OK, dog shouting up that tree again but....I recently had a problem under making progress from a steady speed and it felt like fuel starvation. Gradually got worse to the point that 80 was a mystical figure......er kmh of coarse Kept splutering like a good un but not stopping. Turned out to be the coil. Did seem very rev orientated.

As I said mutus maximus hollering up treeus maximus.

[Darren350]

OK Ill have a bark up another tree ! Had a similar problem with a MGRV8 spent weeks testing and changing bits got really P****d off found to be petrol filler cap breather hole bunged up so car ran ok for a short while and then when you asked for a big shot of optimax the vacuum in the tank said NO NO NO and NO NO go !!!! a few mins later ok again when vacuum subsided !!!!! I know it sounds daft but you could take the cap and and give it a go what you got to loose. Like I say this is probably the wrong tree in the wrong wood in the wrong county but who knows?

[bobfrance]

Has a similar problem in my 400SE, except mine was more likely to cut out when going over a bump than heavy acceleration (although it did that too).

I found the problem whilst removing some old alarm wiring - dodgy connector.

Not that I'm any kind of expert - but my chief suspect (especially with TVRs) would be the wiring, although finding the problem can be a nightmare. I'd tend to use the wiggle each wire and see if the engine cuts out technique (though not whilst driving obviously).

[ScumbagAdie]

For everyones info it was the connection to the Air Flow Meter. Wiggle it and the engine changes speed!

[gun metal]

ScumbagAdie said:

For everyones info it was the connection to the Air Flow Meter. Wiggle it and the engine changes speed!

Are the air hoses to the plenum chamber and air filter in good condition? That can cause cutting out if there is a split letting air in under load, as there is more vacuum.

[350zwelgje]

jmorgan said:

OK, dog shouting up that tree again but....I recently had a problem under making progress from a steady speed and it felt like fuel starvation. Gradually got worse to the point that 80 was a mystical figure......er kmh of coarse Kept splutering like a good un but not stopping. Turned out to be the coil. Did seem very rev orientated. As I said mutus maximus hollering up treeus maximus.

Seems like I have your problem now! When I fix it, probably someone else will get the same problem.
So wedges have 'they all do that sir' and 'relay race' problems?

Rob