M42 hesitation and hard start.

[Sarc]

Over the past couple months I've been experiencing (what I think to be) fuel related problems with my M42 equipped 318is (135K miles). Starting this winter, when we were experiencing single digit temps, it would take a good 30 seconds of turning over for the car to fire up. Once started, an overly lumpy idle would soon be followed by normal idling.
After that, while performing spirited driving in the backroads, I would experience some flat spot hesitation in the upper rpm range (3500-5000). Other normal driving situations were fine.

This morning, since it was 46 degrees, I thought the car would start no problem. It took just as long to fire up as when it was 4 degrees out. A new problem has surfaced as when driving under normal conditions (accelerating from a stoplight/accelerating in 3rd while cruising 30mph) the car hesitates significantly, as if the car is running on 2 cylinders.

I'm automatically suspecting the fuel pump, especially since these symptoms echo those found in the archives. The only symptom I don't have is a whining fuel pump; the pump has been silent.

Any suggestions?

[Jeron]

Fuel filter and fuel pressure regulator could account for all of it.

Vac leak for hesitation and possibly slow starting.

Coil, plugs, and wires for hesitation possibly a slow start.

[marko666]

crank position sensor was causing my car to start badly when cold - bad MAF sensor was causing hesitation & buckling acceleration - also check all of your rubber intake boots, as they could be cracked causing vacum leak. good luck...

Originally Posted by Sarc

Over the past couple months I've been experiencing (what I think to be) fuel related problems with my M42 equipped 318is (135K miles). Starting this winter, when we were experiencing single digit temps, it would take a good 30 seconds of turning over for the car to fire up. Once started, an overly lumpy idle would soon be followed by normal idling.
After that, while performing spirited driving in the backroads, I would experience some flat spot hesitation in the upper rpm range (3500-5000). Other normal driving situations were fine.

This morning, since it was 46 degrees, I thought the car would start no problem. It took just as long to fire up as when it was 4 degrees out. A new problem has surfaced as when driving under normal conditions (accelerating from a stoplight/accelerating in 3rd while cruising 30mph) the car hesitates significantly, as if the car is running on 2 cylinders.

I'm automatically suspecting the fuel pump, especially since these symptoms echo those found in the archives. The only symptom I don't have is a whining fuel pump; the pump has been silent.

Any suggestions?