random flat spots while accelerating

[jimbob29]

my 320i randomly hesitates while accelerating or over taking. one minute its fine and then not.thers nothing wrong with the idol and doesnt cut out at junctions.runs as smooth as silk and doesnt burn fuel.have completely cleaned throttle body and checked how far the plate opens before it clicks thats ok.replaced dizzy cap and arm. plugs are recently new ngk.have checked and cleaned every connection with contact cleaner and checked for corrosion and air leaks and have cleaned and checked the air flow meter flap all is ok.the engine runs amazingly apart from whats mention

[Barx325i]

it could well be a faulty earth strap. what happens to your instruments when it occurs?

[jimbob29]

The engine coolant level light randomly comes on when the coolant is full?

[mrLEE30]

no this is likely to be a sesnor fault in the expansion tank,

what he means is what does your tachometer do when it judders, (i.e drop like a stone to 0 RPM, or just slowly fall down) do you get any lights under the clusters coming on?

[jimbob29]

No nothing like that mate just bogs down randomly at any revs when accelerating then it will clear a be normall and smooth again but just annoying when trying to over take because it could bog down then I'll have to back off.the only thing I haven't checked are the injectors and fuel filter and earth straps its even worse when raining or damp out side if that helps?just wish I moved of the island so someone on here could come and have a look lol.ill clean the earth straps and see what happens.

[Barx325i]

hmm, sounds suspiciously fuel/fuel pump related. possibly a faulty crankshaft sensor or similar..

[Speedtouch]

Try disconnecting the battery or ECU and leaving it for an hour or so to reset it, then reconnect, let the engine idle for at least 10 minutes to eanble base idle settings to be learnt, switch off, restart, then take it for a drive throughout the rev range.

This ensures full transfer of all the program from the EPROM chip to the processor.

Failing that, I suggest fitting a Mild or Wild chip to iron out the flat spots that exist in the standard program.

[iDreamBeemer]

mine has been doing this recently too, did you get to the cause of the problem?

[iDreamBeemer]

Just in case it helps anyone, I found out the problem on mine...it was a dodgy earth to the fuel pump. New earth fitted and its back to running nice again.

Now to sort out the rust...lol