BMW sputters 10 seconds after startup

[JHZR2]

Hi,

A few weeks back I posted about our toyota previa that sputters at the first cold startup, stalls, and then after it is started a second time runs fine.

Well, Im having a similar issue with my 91 BMW 318i. The first thing to note, however, is the two vehicles are at different ends of the state, and fuel up at completely different stations, etc.

OK, so here is the deal: this past weekend, I ran the tank pretty low. With the tank near empty (though the light wasnt quite on yet), I let the car sit overnight. The next morning, I started it, and it started as usual, however after about 10 seconds of sitting, it started sputtering really bad. The tach went down to ~350 RPM, and it felt like it was going to die. However, it didnt, and the engine caught itself back up to speed, and it was 100% fine for driving to do errands, including some highway miles. This had never happened before, so it is a brand new issue.

It sat for another day, with the tank as low, and at startup, it did the same thing. Shortly thereafter, I refilled with conoco top-tier gas, and added some fuel power.

Yesterday morning, I just went out and restarted the car, and it didnt happen. I thought maybe with the fuel so low, the fuel pump was loosing its prime, and so there was an air bubble in the line when it sat for too long, due to fuel flowing back out (?

). Anyway, I was happy, and hoped that the issue went away as fast as it had shown up.

However, this morning I started the car, and it sputtered again, with a full tank of fuel. After it sputters and nearly stalls, it runs fine and it does not happen again. The engine runs very smoothly and has good power - idle is smooth as silk, and there is no vibration, cruising at 75 mph is very nice. Mileage is still consistent at ~29.5 MPG average each tank.

I do have the BMW factory check valve retrofit, so I dont think the fuel lines are draining or doing anything funny. There is no signs of gas odor, so I doubt that is an issue either. TB is clean, all vacuum hoses are fine, no signs of any other issues. Ive never had a CEL.

Any ideas/suggestions? Is this a sign of a bad fuel pressure regulator? Sign that my fuel pump is on the out (I wouldnt doubt that, though FP has made it MUCh quieter!)

Any info would be really great!

Thanks,

JMH

 

[Alan]

Does this model still have the cold start valve on it?

Have you changed the fuel filter?

 

[JHZR2]

fuel filter is about a year old, no sigs of the filter being bad - wouldnt I have fuel problems on hills, high transient loads, etc?

The M42 engine does not have a cold start injector...

Thanks!

JMH

 

[Alan]

Maybe the intake/throttle body needs cleaning?

 

[JHZR2]

did it not too long ago - it is a two orifice system, so there are two throttle plates or whatever they are called to clean - I got them both very well, and they still are clean as can be.

JMH

 

[theguru]

Maybe you picked up some water/ debris from bottom of tank. A suggestion- remove fuel filter and tip out the fuel from the inlet (tank side). Examine and if not too dirty reinstall, otherwise install new filter. Maybe the filter sock on the fuel pump is partially blocked is another possibility.

If possible get your fuel pressure checked, maybe the pump is on the way out.

 

[mechtech]

Do you have an accumulator on the car? If so, that would be a good guess for the problem.
How about two fuel pumps? One in the tank, and one underneath the car. The in tank pump may be weak/bad.

 

[VaderSS]

Interesting. My Festiva loses power for a couple of seconds, not a sputter, just an almolst complete loss of power, about 20-30 seconds after start up. I never notice it unless I take off right away, after startup, but it happens every time if I do.

 

[Alan]

Could very well still be a vacuum leak which shows up the most when the engine is cold.Intake manifold gaskets and fuel injector gaskets could be the problem.