2003 3.0 stumbles on cold start

[Oldmactech]

My 3.0 stumbles very briefly on startup at cold start (not on warm start)

Fuel pump maybe?


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[andrewwynn]

Fuel pump shouldn't go away after warmed up and worst on full throttle.

My e70 does same and I suspect it's plugs which I already have the replacements

[80stech]

On the M54 it could be that the brake booster/grommet is leaking. Spark plugs are critical with individual coils because they produce a lot less voltage than old school coils, also going to an iridium or ruthenium plug with wire electrodes can be a big improvement in igniting fuel mixture. My E70 had a stumble (sometimes stall) after starting and it turned out to be carbon build up from the previous owner not using premium fuel, a few tank fulls of premium was the answer to that.

[getty150]

If you're not keeping the oil clean it could very well be the vanos solenoid especially if it presents it self during stops and trying to power up hills.

[Oldmactech]

Hmm, I’ve been getting random DSC/engine failure lights, wonder if the brake issue relates?
Also, I swapped in new brake pads last week, symptom started shortly after. No way that’s related, right?


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[Oldmactech]

I’m due for oil, plugs are 10-12k miles in.


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[andrewwynn]

Any codes? Weak coil can give your symptom

[ewebby]

check the area around your plugs, I had same issue and it turned out to be old rubber from socket fell in and did not let one of the coils seat all the way.

[Effduration]

OP - Are you losing any coolant?

[Oldmactech]

No coolant loss.
Idle control valve throws a code.
Now it stumbles on start but smoothed out 4-5 seconds in, fine after.
Other morning it stumbled for several mins, reset the code, drove fine afterward.


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