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E39 cold start problem - resolved with a restart?

8932 Views 66 Replies 10 Participants Last post by  borntodeal, 
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Hello,

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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C
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.
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How old is your battery ? Is it AGM -- it does not like cold weather- ?? I assume your tech did check and test the battery and alternator before throwing all those parts at the car.
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Well, not to steal your thread, but I'd like to know the actual cause myself, as I am having the same problem with my car.

As I recently did some major engine work (valves, heads, timing chains and guides) I have installed a new battery-fully charged-, new alternator, new MAF, and new fuel pump. But the car does not want to start: it cranks well for about 10 seconds and then dies. And it gives no error codes..!!

Though this year we have a cold winter in my neck-of-wood , with a max daily temp of 45 degrees. So, maybe ..?..:mad:
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Yep.
After making sure the fuel pressure, battery voltage and vaccum-air supply are ok, some internet denizens point to the ignition switch or fuel pump relay as the most likely culprits. They can get stuck open or closed in cold weather.
Others prefer pointing to the camshaft or crankshaft sensors, though I doubt it. Because these sensors normally leave an error code when if they fail or malfunction. And I do not have any error code present in this situation.
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Alright, then we are left with the ignition switch : Does it get stuck or freeze in cold weather ? Any quick test to verify that it is working , short of removing its cover and probing its pins with a multi-meter??
Or is it an electric connection to the starter that gets stuck ??
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Try to check or replace the starter relay instead. As mattmar1 points out, if there is fuel pressure at the rails, then the fuel pump relay is probably ok.
I'd suspect the ignition switch, or the starter relay.
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