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E39 cold start problem - resolved with a restart?

8886 Views 66 Replies 10 Participants Last post by  borntodeal

I have a 2003 530i that has a hard time when it's cold outside. Yesterday the temperature was about 16C (in Toronto), so it was below 20C for the first time in few months and the car started but there was no power. Eventually when I had stopped at a stop sign the car gave me errors and was about to shut down so I turned it off. Right away I started it and it started just find. No codes, no loss of power...nothing wrong, perfectly fine!

This is not the first time it has happened. I had cold start problems with it last winter, but the problem was always resolved by restarting the engine.

My question is this: what can cause cold start problems that can be resolved with a restart?

^The reason I am phrasing the question like this because there are a lot of things that can cause a cold start problem but don't get resolved with a restart. I am trying to narrow down the list by knowing that an immediate restart always resolved the problem!

Thank you in advance for your help! :)
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I'd try to do some basic engine tune-up hygiene:

-- Clean or replace the intake air filter
-- clean the MAF, and the throttle body plates (front and back) with CRC
-- Inspect, clean or replace the spark plugs
-- Check, clean or replace the fuel pump and fuel filter
-- Run a scan for any stored error codes. Clear them and reset the adaptations

Then test again.
I appreciate your insights here. I own a 2002 E39 (530i) and it runs nicely and has been serving me well for over 10 years.

Very recently, it has had a hard time cold starting below 60 degrees outside. I use starter spray and that helps a bit. Eventually, after some amount of cranking it will start up. Once running, it is operating smoothly.

I read all of the above and I wanted to ask your opinion about this situation.

Labor in LA is pretty high and I've found that the very honest mechanic I use will typically just replace what is wrong with my car and then other things start failing along the way, e.g. he replaced one coil then three more failed. I asked him to simply replace them all and spark plugs too.

If you were to suggest all possible things causing the cold start and if I wanted to simply replace everything that could be potentially going wrong that is causing hard cold starts, what would be your list of items to replace with new that would eliminate most possibilities?
Thank you for your response. This is a 2002 and I have never replaced the fuel filter, the fuel pump, or the injectors. Would you recommend having them all replaced as a matter of course? The vehicle has more than 210,000 miles on it.
Thank you so much for this advice, where do recommend purchasing these two items? The local mechanic buys aftermarket from a local distributor and I'd prefer to buy parts when I can see other customer reviews.
You are very generous with your time. Thank you. My vehicle only has a hard time starting cold. Replacing coils and plugs is easy for me to do and costs very little, do you recommend that also?
I just returned from the shop and the technician states the fuel pump is good, he wants to replace both camshaft sensors and the rear oxygen sensor upstream. He suggested that I order the parts. The local distributor is pricey (he said). He is a good guy. He recommended all three because they are throwing codes and because the labor is minimal about two hours total. Do you have any brands you like?
Thank you for all your advice. It is resolved.
Thank you so much for all your generous help and advice.

Great question, we are replacing the oxygen sensors and camshaft position sensors. This has not yet occurred, but that was the suspected cause.

If your BMW is throwing those codes, that may help.
Hey again, I'm not the mechanic and he's occupied today and we'll replace the sensors and see if the cold start problem persists.
We replaced two oxygen sensors and crankshaft sensors and the vehicle is starting better. I still have a hard start occasionally so we will also be replacing the camshaft sensor and see what happens.
My 2002 530i simply won't start below 45 degrees F. What are the usual causes of this? It starts instantly when it warms up, so I am not sure where to look. I already paid the mechanic to replace the mass airflow meter, the oxygen that did not work. I'd like to save money by trying less expensive solutions! Any ideas?
wait....thought this was resolved.
Me too. I was in San Jacento and it became very cold and my vehicle did not start. After the outside air rises above 45, it started. I am back to the drawing board.
Neither of those parts has been replaced. Would these two items cause the engine to not start at all under 45 degrees and start instantly after 45 degrees?
Hello all, to-date, the mechanic has not fixed my issue.
He has completed all of the following repairs:
  1. replaced two oxygen sensors
  2. replaced the mass airflow meter
  3. replaced both camshaft sensors
  4. replaced the crankshaft sensor
  5. replaced the fuel filter
  6. air mass meter boot which was cracked
  7. brake vacuum valve which was cracked
I arose early this morning to cold start my 2002 530i and it won't start at 45 degrees F.

What else could the issue be?

The vehicle starts and runs perfectly when the ambient temperature is warmer.
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Someone I spoke with thinks that the coils and plugs should be changed to see if that corrects the issue. Are these vulnerable to cold temperatures?
Point well made. Thank you. What else could possibly cause no start in the 40's and low 50's and instant start-up when the ambient temperature is higher? Could it be a relay?
relay possible, could be binding mechanically...any electric or or electronic component possible. is 45 the cutoff point? wont start below 45 as well?
It will never start below 45 degrees. Which relay?
Break out the heat gun, stick it underneath the hood and warm up the DME/ECU. If that doesn’t work, heat up the back of the glove box with it where your fuel pump relay is, just don’t melt anything. Get an Infrared temp gauge and when it gets to 45 degrees in those spots, try and start it. Maybe there is a connection that is right on the edge of being broken. I guess I’d be trying something like that. Just go easy with the heat gun.
Very wise idea, how about just a hair dryer? That won't melt anything and gets pretty warm.
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