[mteel]

Long time reader. First post...

I have been trying to diagnose a rough idle on start (cold or hot) for several months. The car has 115000 miles on it so I have been replacing things as I go. So far I have:

Replaced both Vanos Solenoids
Replaced CVV (oil separator) and all hoses
Replaced all spark plugs
Replaced all coil on plugs
Cleaned the MAF sensor
Replaced upstream O2 sensors
Replaced Eccentric shaft actuator (motor)
Ran two bottles of Chevron Concentrate Plus Fuel Injector cleaner through (not at same time)

When cold or hot when first started it "hunts" from 800-1200 RPM. It seems that once the "choking mechanism" is opened/deactivated/etc. it will idle like a swiss watch at about 600 RPM. Runs great other than the idling problem.

Any ideas what to look at next?

Thanks!

[_Sinister_]

IDK for sure but maybe time for walnut blast
Check this link OP
http://www.e90post.com/forums/showthread.php?t=682116
^

[mteel]

BTW, the eccentric shaft sensor looks fine.

[mteel]

Originally Posted by _Sinister_

IDK for sure but maybe time for walnut blast
Check this link OP
http://www.e90post.com/forums/showthread.php?t=682116
^

Thanks, that's interesting but too much $$$ for the tool for one car. I guess I could take it to someone to do but it would be 50+ miles from home.

Any other ideas for things I can reasonably do?

[_Sinister_]

There are plenty of small shops that offer such cleanings just got to do a search for them.

[NGEE]

Doesn't intake walnut blast only apply to turbo-charged cars?

[GoRomeo]

I am almost positive you have a leaky injector.

[NGEE]

Originally Posted by GoRomeo

I am almost positive you have a leaky injector.

Would this settle after warm-up?

[Chriztofor]

See my sig below.

[mteel]

I've run 2 bottles of the Chevron through it in the last 6 weeks. I have the BavTech tool, scanned ad nauseum, nothing interesting in any fault codes.

[mteel]

Originally Posted by NGEE

Would this settle after warm-up?

My thoughts too - if it were an injector why would it improve when the engine is warm?

[GoRomeo]

If you have not troubleshooted for injector leaks, it's best to pull all of them and service each one. If you can DIY see below:

In order to access them, first pull your fuel pump fuse and run the car til it dies. Then you'll need to get all the basic stuff out of the way and remove the injector harness, which is quite a pain in the arse. Once you've exposed the rail in it's entirety, there are two 10mm nuts and nothing more. Leave the clips that hold the injectors to the rails and give them a tug. Don't fear them. They won't break and the rail won't bend. Now position them in a low plastic container to catch any gas that remains in the line. Pull the clips and remove the injectors. You are now ready to service them with an appropriate kit.

[GoRomeo]

Originally Posted by mteel

My thoughts too - if it were an injector why would it improve when the engine is warm?

Not quite, A while back, some one posted that have been having warm start up issues. Namely, when he start the car for the first time of the day everything was fine. However, after the car was driven then turned off and sits for over 30 minutes it would not start on the first crank. It starts on the second attempt, idles rough, He would hit the gas and everything was ok but still rough idling due to a leaky injector.

[mteel]

Originally Posted by GoRomeo

Not quite, A while back, some one posted that have been having warm start up issues. Namely, when he start the car for the first time of the day everything was fine. However, after the car was driven then turned off and sits for over 30 minutes it would not start on the first crank. It starts on the second attempt, idles rough, He would hit the gas and everything was ok but still rough idling due to a leaky injector.

Thanks. My problem is both cold and warm startup until the ECU decides it's warm enough to drop the idle down to 600 or so. When cold that is 2-5 minutes; when warm it is 30secs-1min. Do you still think it could be injectors and if so why does it improve cold or warm?

I can DIY and servicing the injectors sounds like a good idea anyway. Any links to point me to for doing it? Thanks again.

[MrZ]

Any codes stored? If so, is it a 1-2 cylinder misfire or multiple cylinder misfire? That will eliminate a few things.

I forgot whether there's an ICV on n52. If there is one, check it. Also, did you check for vacuum leaks? Theoretically it would be worse when the engine is cold.

[Casca]

Originally Posted by mteel

I've run 2 bottles of the Chevron through it in the last 6 weeks. I have the BavTech tool, scanned ad nauseum, nothing interesting in any fault codes.

Chevron has http://www.amazon.com/Chevron-9280-6...A8YGJGFCBS27F8

and

http://www.amazon.com/Chevron-67740-...ywords=techron

Not really the same thing. Which did you run two bottles of? One is very low % of PEA (polyether amine) meant for maintaining an already clean fuel injectors/system and the other is up to 32% PEA meant for cleaning a dirty system followed by an oil change.

I'd go with 3M. It supposedly has 40% to 60% PEA
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

If it doesn't help, I'd also remove the injectors and bath them for a while in the 3M stuff and if you can, cycle it through the injectors. Not sure on the process, totally research cleaning injectors before doing it.

[mteel]

Originally Posted by Casca

Chevron has http://www.amazon.com/Chevron-9280-6...A8YGJGFCBS27F8

and

http://www.amazon.com/Chevron-67740-...ywords=techron

Not really the same thing. Which did you run two bottles of? One is very low % of PEA (polyether amine) meant for maintaining an already clean fuel injectors/system and the other is up to 32% PEA meant for cleaning a dirty system followed by an oil change.

I'd go with 3M. It supposedly has 40% to 60% PEA
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

If it doesn't help, I'd also remove the injectors and bath them for a while in the 3M stuff and if you can, cycle it through the injectors. Not sure on the process, totally research cleaning injectors before doing it.

The latter (concentrate plus). Selected based on other posts.

[mteel]

Originally Posted by MrZ

Any codes stored? If so, is it a 1-2 cylinder misfire or multiple cylinder misfire? That will eliminate a few things.

I forgot whether there's an ICV on n52. If there is one, check it. Also, did you check for vacuum leaks? Theoretically it would be worse when the engine is cold.

No codes stored since replacing the vanos solenoids and cleaning the MAF sensor. No BMW-specific codes either using the Bavarian Technic SW and cable. There is no ICV on N52, just the DISA. It looked fine when I had the intake manifold off for the CVV replacement.

[asus389]

How old is your battery? Sounds like a silly question, but I had similar problems on my 06 325i for like a year before my battery finally gave out. New battery, and it idles much smoother after start.

[mteel]

Originally Posted by asus389

How old is your battery? Sounds like a silly question, but I had similar problems on my 06 325i for like a year before my battery finally gave out. New battery, and it idles much smoother after start.

I have no idea - I bought the car about 18 months ago. Cranks just fine first thing in the morning.

[Bimmertech113]

I think there is a software fix for that issue but I'm not sure

[trk06]

Originally Posted by mteel

Thanks. My problem is both cold and warm startup until the ECU decides it's warm enough to drop the idle down to 600 or so. When cold that is 2-5 minutes; when warm it is 30secs-1min. Do you still think it could be injectors and if so why does it improve cold or warm?

I can DIY and servicing the injectors sounds like a good idea anyway. Any links to point me to for doing it? Thanks again.

my car has been doing the same for years. It starts right away and once the RPM settles around 600 rpm all good.