E39 cold start problem - resolved with a restart?

8885 Views 66 Replies 10 Participants Last post by borntodeal, 3 mo ago

wc123wc

Discussion Starter · Sep 13, 2018

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!

1 - 20 of 67 Posts

mattmar1

· #4 · Sep 13, 2018

the Misfire Cylinder 2 With Fuel Cut-Off is the reason it runs rough when cold. when shutting off and restarting, the error is cleared (but the code is stored) and it runs on its way. once the code sets with the engine running, the injector in the corresponding cylinder is turned off, as the engine is detecting a misfire, and may be dumping raw gas in to the cat.
i understand that this is a code from a coupla years ago. clear all codes, wait til it does it again and see what you get back codewise. if its the same (misfire with fuel cut off#2) id swap the plug and coil with another cylinder. clear codes, and see what happens next (same code or does the code follow the swap?)
then we can go from there.

mattmar1

· #9 · Sep 28, 2018

might give thought to checking fuel pressure at the injector rail. did you swap any plugs or coils?

mattmar1

· #12 · 7 mo ago

fuel pump is possible. check the fuel pressure when its running (there is a schrader valve on the fuel rail), should be reading 50 psi. then after engine shutoff it should only drop a small amount in the first hour. there is a check valve in the fuel pump that is supposed to keep the pressure up, and when the key is turned to pos 2 the pump will run for 2 seconds to prime, but if theres no fuel in the line it doesnt have a chance to. do you have a smell of gas when trying to start the car? an injector can be leaking and giving the same result.

mattmar1

· #14 · 7 mo ago (Edited)

depends on if you willing to just throw money at it or of diagnose and correct it. if the pump and filter have 200+k miles on em and theyre original, i would replace them as a PM thing.

mattmar1

· #16 · 7 mo ago

pierburg brand for the fuel pump, mahle for the filter. aftermarket for the pump is questionable.
getting a read of your fuel pressure will give you info as to where the issue may be, whether were going in the right direction or not. its kind of difficult to figure out across the distance at times. this is just my thoughts on where to start.

mattmar1

· #18 · 7 mo ago

how old are they, or how many miles on them?
found out what the fuel pressure is, preferably after the car sits for an hour or more, yet? then when running?

mattmar1

· #20 · 7 mo ago

oe or oem brand...fcpeuro sells them and offers a lifetime warranty on everything they sell.
he's saying codes for both cam sensors and one of the 02's? those in themselves could cause what youre seeing. werent aware of that earlier?

mattmar1

· #23 · 6 mo ago

and the resolution was? its a good thing to share the info for the next person.

mattmar1

· #25 · 6 mo ago

oh well....glad for ya though

mattmar1

· #28 · 6 mo ago

are you getting CEL or has the DME been read for codes? if any codes, make note of em and list on here, then clear em and see what comes back. kinda hard to tell just by symptoms, different things come to mind from your post. read or have em read by a BMW specific scanner, many generic OBDII readers wont pull up pending or inactive codes, those can and probably are important.

mattmar1

· #33 · 4 mo ago

wait....thought this was resolved.

mattmar1

· #35 · 4 mo ago

any pending codes? or codes at all?

mattmar1

· #37 · 4 mo ago

has either cam position sensor or the thermostat been replaced? if so, were the codes them same beforehand?

mattmar1

· #39 · 4 mo ago

hard to give a definitive answer from a distance. however i have experienced an intermittent hard start ( dunno if temp came in to play) from a cam sensor, replaced it no other issues since. the cam sensors are a semiconductor device, and can become temp sensitive. in your post #27, you stated that your mechanic was replacing the cam sensor(s). did this not happen? and btw, only replace with OE or OEM parts. many aftermarket parts dont work reliably, last long, some even arrive DOA.

mattmar1

· #42 · 4 mo ago

not really....its worth looking at but it would take 6 separate cylinder failures to cause...seems as if youve a common point of fail issue

mattmar1

· #44 · 4 mo ago

relay possible, could be binding mechanically...any electric or or electronic component possible. is 45 the cutoff point? wont start below 45 as well?

mattmar1

· #46 · 4 mo ago

fuel pump? DME?

mattmar1

· #50 · 4 mo ago

itll work, just take longer

mattmar1

· #53 · 4 mo ago

not saying this has happened to you, but there are fake parts to be found around...

mattmar1

· #59 · 4 mo ago

the FP relay has been brought up, nothing has been stated whether its output has been been checked or the relay changed. if fuel pressure is there, the relay is working.

1 - 20 of 67 Posts