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Discussion Starter #1 (Edited)
2004 M54 330i petrol auto

Greetings all from a newbie, just looking for some more check points to a non starting engine. Symptoms have gradually got worse over several weeks and now failing to start with continous cranking. I've listed checks and parts replaced so far as follows:

Difficult starting engine from cold with symptoms of very poor idle (100 to 300 rpm) and stalling. Once started after 3 to 5 attempts, engine runs very lumpy and pumping the accellerator pedal has no affect or any increase to the rpm. After around 30 secs of lumpy idle, the engine becomes smoother and idle rpm becomes normal. Vehicle drives moderately fine after warming up but still has some irratic idle with hesitant acceleration. Occasional misfires with CEL and fuel cutoff on cylinder 3 and 5 which clear after a code reset with basic OBD tool.

Visual inspections completed:
no smoke, no overheating, no coolant/oil/fuel loss and no coolant/oil mixing.
No codes or sensor codes apart from occasional misfire code on cylinder 3 and 5.

Check points and parts replaced:
Swapping coils and Replacing all 6 with new.
Cleaning spark plugs and Replacing all 6 with new.
Start with MAF disconnected/connected and New MAF.
Vacuum leak test with compressed air.
Replace Radiator lower Coolant Temp Sensor.

Previous major work carried out after a burst exapnsion tank (stuck closed thermostat)
and several months before the above symptoms:
New coolant hoses, expansion tank and coolant cap.
New water pump, thermostat and viscous fan.

I dont have access to any compression/pressure testers but looking at possible
fuel pump or injectors but also possible valve/cylinder compression issue.
Not wanting to spend more on replacement parts if also possible head gasket or
crack in cyclinder or stuck valve causing poor compression.

Any advice or additional pointers greatly appreciateda dn thanks for reading.
 

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Do you hear the fuel pump priming?
If I were you, I would check the fuel pressure at the rail before everything. Verify that you have the correct pressure first.
 

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Please stop throwing parts at the problem. Doing so wastes money, doesn’t fix the problem and it angers the BMW goddesses. Take the car to a reputable indie shop that specializes in bimmers.
 

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Discussion Starter #4
Do you hear the fuel pump priming?
If I were you, I would check the fuel pressure at the rail before everything. Verify that you have the correct pressure first.
thanks, yes that was my next stage when I got hold of a pressure tester. This is certainly not a simple coil/plug issue but I do smell fuel when cranking. I have noticed that fuel pump when priming is not as audible as it used to be, I used to hear a 3 second buzz on ignition but now it is very faint to hear.
 

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Discussion Starter #5 (Edited)
Please stop throwing parts at the problem. Doing so wastes money, doesn't fix the problem and it angers the BMW goddesses. Take the car to a reputable indie shop that specializes in bimmers.
thanks for chpping in, but taking it to a shop is wasting just as much money as pot lucking parts. The specialist charge hundreds just to diagnose a fault and then hundreds to fix it. So far I've only purchased service parts which were needed anyway. I expect a shop will spend 2-3+ hours diagnosing which is close to £150 labour. A VANOS diagnostics on this motor will bankrupt me and cost far more than the vehicles value. Would much rather attempt a repair myself. I know these shops need to make a living and business rates are high, but if they all had a flat basic rate charge just to diagnose the fault instead of an hourly rate then yes, I would take to an indie.
 

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Discussion Starter #6
Just an update on the situation so far. I've had a fuel pressure test and fuel pump checked, both are good and fuel pressure is ok at the injector rail.
An auto-techinicain suspects the issue is timing as the spark is not igniting the fuel a the correct time. Not sure how the timing could have gone as I thought these engines had a timing chain which prevented them from slipping?

Anyway, looks like a too big a job to tackle and far too expensive to pay a specialist to do. If anyone suspects anything other than timing I would be very interested to know.
 
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