BMW Repair: Cold Starting Problems with 320i, cold crank, 6 digits

Question
Tino,

See below for details on previous request in which you requested the last 6 digits from the VIN.

VIN - WBACB2327RFA20675

And a few more items of interest:
- when the car is idling rough it also barely drives and can only go maybe 10kw per hour with no hill present.
- it is a 1994 with 243,000 km's on it
- the last emissions testing on it 1 year ago still passed but showed higher than average NOx's.
- about 20% of the time, I can actually get it running perfectly with the engine still complete cold. For example, last night, after sitting for ~4 hours ourside, it started up right away and it was 4 degrees Celsius outside.
- last winter it often took 2-3 seconds to cold crank the engine but it always ran great afterwards.

This last items, leads me to believe that there may be two issues with the car, with one of them being the starter (maybe its on its way out?).

Thanks again for your suggestions.

Craig

**********************

In the past month it has become colder in Vancouver, Canada and this has corresponded with starting problems with my 320I. A summary of the problem is this:
- below ~10 deg.C the car takes 4-5 seconds to turn over
- once started it idles extremely rough, like it is only firing on a few cylinders. Speed is approximately 550rpm and headlights almost flicker as it struggles to keep running.
- above 1000rpm it is fine
- hitting the gas brings the rpm's up to a maximum of 2500rpm, at which point it abruptly cuts back to 2100rpm and tries again.
- if it is below freezing, it can also stall if left to idle
- the only way to get it running properly is to turn off the car and start it again, at which point it runs great.
- generally, the colder it is the more number of starts it takes before it "catches" and runs good.
- occasionally, it will run good on the second start even if the engine is still cold, but mostly it has to rest for a while (5 minutes) after idling for a couple of minutes.
- the check engine light never comes on or returns any error codes (I believe I have OBD I but haven't looked into yet).
- I don't have a stock BMW battery in the trunk (long story), but it does meet the technical specifications for the original (although it is about 20% smaller).

I have only had the car two years now and have only had to do basic maintenance so far, but I don't know where to start on this one.

Two other items:
- when I changed the spark plugs 4 weeks ago and checked the coils I discovered some oil on spark plug #6. I cleaned off the "boot" and replaced the plug at that time. I checked it a week later and it was still clean. I haven't checked it again in the past two weeks because my starting problem didn't seem to be related to it.
- occasionally I can smell gasoline when idling the car. Seems to come from around the air intake manifold area.

Sorry about the length of details. I figured the more I could give you the better.

Any suggestions on where to start.

Thanks so much for your help.

Craig Peterson


Answer
Hi Craig,
You seem to have a multi-faceted situation here which is common to  not so new vehicles. With time and use, so many things can bring problems in a car, some distinctly recognizable, some subtly intermingled with others thereby making it hard to make a quick and firm diagnosis.
Couple that with sub-zero weather and you can really have a headache.
So go down to basics and use common sense. Remember that even a Royce left in the open in below zero would have a hard time starting. That is why some put heating blankets on top of their engines. Note too that a battery would not be able to give full power at low temperatures. And that the radiator coolant should be properly constituted to compensate for cold weather (the usual 50/50 mix may not be sufficient below zero. But a starter should still crank the engine and the engine should still start even in sub-zero provided it has not been frozen stiff for a lengthy time.Of course the cranking may be slower, and smooth running can only be achieved after  warm up.
I see 2 basic problems here. That of starting, and that of running properly once started.
You can not do anything about the cold affecting the battery, or the starter or the many joints of the engine that has to move while it is below zero not unless you bring it inside a garage and maintain a warm environment.
But the bad running is something else.
Start by replacing the fuel filter and checking the fuel pressure at the pressure regulator. Fuel pressure should be checked before turning on the key (at least 8 to 10 psi), after turning on the key (momentarily the pump should power up and boost pressure up to operating pressure or at least substantially higher than 8 to 10 psi), and with engine running (35 to 45 psi). The fuel pump could be bad or the pressure regulator might not be doing its work.
Then check all the rubber hoses (basically vacuum related) that connects to the intake manifold. This includes the big rubber boots that connects the air filter, airflow meter and throttle valve, the idle air valve, fuel pressure regulator, etc. etc. Replace all defective ones. If none is found, replace the idle air valve. Or replace all bad hoses including the idle air valve.
Then check the ignition coils if they are firing the plugs properly. You would need fairly sophisticated equipment to do this (oscilloscope/lab scope). Replace coils and boots as needed (never replace coils only, always replace both).
There are still other possibilities but you can start your diagnostic procedure by doing the above.
Tino