P1345 codes and rough idle at cold startup issues

[Quattro Pete]

This is on my 2002 530i (M54 engine) with 111K miles.

On cold engine start up (the colder it is outside, the more likely the symptoms will manifest themselves), I am getting rough idle sometimes. Often times the rough idle goes away once I start driving. Sometimes it doesn't. In those cases when it doesn't, even when accelerating on the highway, I could feel the engine not firing on all cylinders. Sometimes I get the "Service Engine Soon" light . Then I pulled over and switched the engine off. After a few minutes when I turned it back on, the engine ran fine - no misfires anymore. There are some error codes stored.

Based on my google search, specific to BMW world, these are:
P1345 - Misfire Cylinder 2 With Fuel Cut-off
P1346 - Misfire During Start Cylinder 3


Now, this rough idle would sporadically show up ever since the car had about 40k miles after the car sat for days. But it seems like this issue pops up more and more often these days. This morning was actually worse than usual. The car sat unused for 4 days (in unheated garage). I started it this morning, and it ran so rough that it died. I waited a bit and restarted, and kept RPMs higher, and after a while it started running smoothly again.


Spark plugs were replaced at 42k miles. Probably time to replace them again, but the issue was there even before that.
CCV was replaced at 57k miles.
O2 sensors are still original, AFAIK.

Your thoughts as to what could be the most likely culprit? Coils? Fuel injectors? I tried asking on one BMW forum, but did not get a whole lot of good ideas. I might have to take it into the local indy shop after this winter, but if they can't reproduce the issue, they probably won't do much for me.

 

[dbias]

Id look at the injector on cylinder 2.

 

[toneydoc]

Maybe look for some corrosion on coil to plug connection

 

[Trav]

Start with the simple things, plugs and vacuum leaks. Your fuel trim data should expose a vacuum leak. After that look for possibly a bad CPS or coil. Injector is doubtful as you have multiple cyl misfires.

 

[OVERKILL]

My sister's car (2003 330i) was doing something quite similar. Ended up being a tear in the boot that goes between the MAF and the TB and it progressively got bigger which made the symptoms worse.

 

[Trav]

That would show up in the fuel trim readings also. In the rubber type this is common, plastic not so much. FT data would be helpful in this case.

 

[Warstud]

It sounds like this problem all started after you changed the plugs. Did you use OEM plugs ?

 

[Audios]

Time for plugs 100%. Use the BKR6EQUP. Move the coils around, mark where they came from, clear faults and go for another ride. See if the faults follows the coil or stays in that cylinder. Are you getting any smoke out the tail pipe? How does it restart after sitting for a few hours as opposed to over night?

 

[Quattro Pete]

Originally Posted by Warstud
It sounds like this problem all started after you changed the plugs. Did you use OEM plugs ?

The problem started before I changed the plugs. I changed the plugs hoping it would solve this problem, but it didn't.

 

[das_peikko]

I'm thinking water temp sensor. If the computer is being told that the temperature is warmer than it actually is (being lied to), the mixture ratio won't be rich enough for cold starts.

 

[Quattro Pete]

Originally Posted by Trav
Your fuel trim data should expose a vacuum leak.
Thanks. Sounds like I'll have to take it to the shop since I have no way to read fuel trims.

 

[Quattro Pete]

Originally Posted by Audios
Time for plugs 100%. Use the BKR6EQUP.
BKR6EQUP is what I have there now, alas they have close to 70K miles on them, so they could certainly use changing. However, I first noticed this this issue at 40K miles. So I changed the plugs at 42K, but it did not fix this problem.

Quote
Are you getting any smoke out the tail pipe? How does it restart after sitting for a few hours as opposed to over night?
Just white smoke - typical during cold weather. Nothing unusual.
If I restart after sitting for a few hours, it runs fine.

 

[Trav]

Originally Posted by Quattro Pete
Originally Posted by Trav
Your fuel trim data should expose a vacuum leak.
Thanks. Sounds like I'll have to take it to the shop since I have no way to read fuel trims.



You should check the plumbing from the MAF to throttle body Overkill mentioned, its runner and tends to crack in the accordion part. Common failure on many cars.

 

[Audios]

Originally Posted by Quattro Pete
Originally Posted by Audios
Time for plugs 100%. Use the BKR6EQUP.
BKR6EQUP is what I have there now, alas they have close to 70K miles on them, so they could certainly use changing. However, I first noticed this this issue at 40K miles. So I changed the plugs at 42K, but it did not fix this problem.

Quote
Are you getting any smoke out the tail pipe? How does it restart after sitting for a few hours as opposed to over night?
Just white smoke - typical during cold weather. Nothing unusual.
If I restart after sitting for a few hours, it runs fine.






Definitely try new plugs and move the coils to rule them out. A torn air boot for vacuum leak would give you misfires on more cylinders along with system too lean faults. The fact thats its determining 2 cylinders means its localized to them, not across all. Rule them out before going further down the line.Not trying to scare you, but this is exactly the symptoms I had with my bad head/gasket in my 05 X3. I chased down absolutely everything before pulling the engine. Allowing it to sit overnight lets the sealed cooling system pressure to weep into the cylinders, and gives you a rough start in the morning. Keeping a pressure tester on the system overnight makes it worse, since it will start at 15 psi. Once I got the head off I noticed a slight crack and a small path between cylinders 4 and 5, faults on those 2 cylinders alone, plus random system too lean bank 2 faults ONLY, not both banks like a typical air leak.

 

[another Todd]

GM was having the same symptom on there Trailblazer inline 6 cyls, in that case it was bad valve seats (loose or otherwise leaking I suppose) and the cure was replacing the head. Vehicles ran fine when warmed up, but had a fairly hard misfire upon first start of the day.

 

[mattd]

.

 

[Quattro Pete]

Found this torn hose. Not sure how I missed it or how long it's been torn.

Apparently this vacuum hose provides a reference of atmospheric pressure to fuel pressure regulator. If this has been torn for quite some time, there is a possibility some dirt got sucked in there and potentially clogged the FPR. One of the BMW guys mentioned that "A plugged up FPR would result in fuel pressure at the injectors being out of spec and thus mess up mixture control by the DME."

Looks like I really need to get a reading of my fuel trims.

 

[Trav]

I think you will be okay, just put a new piece of hose on and try it.

 

[Quattro Pete]

Originally Posted by Trav
I think you will be okay, just put a new piece of hose on and try it.
Will do.

But to Audios' point, wouldn't a vacuum leak cause misfires on all cylinders, and not just a couple?

 

[Trav]

It may or may not depending on where the port is, the size of the leak and what the leak is connected to. This engine uses old style metal Bosch (IIRC a ball nozzle) injectors that when dirty (after 17 years they almost assuredly are) they can sputter under certain conditions especially when it fuel pressure increases like would happen if the FPR is not working properly.
Its called a ms/rpm fail where the ms are low and pressure is higher but it can cause them to stick also when cold or hot.

That may or may not be the issue but I learned a long time ago fix what you know is bad/broken first before getting deeper into it. That looks like a clean air source not a vacuum line but if one hose has failed I strongly suspect there may be others, you need to look at all the hoses carefully especially where they connect for cracks and splits.
You probably need a garage for further testing like fuel pump pressure/FPR and scan tool data.