Engine stumbling on cold acceleration

javis20 · Post by **javis20** » Wed Mar 25, 2020 6:05 pm

Car is a 2011 BMW Z4 50,000 miles. Car stumble on acceleration when cold and has a periodic miss when idling. When the engine is fully warmed up the problem pretty much disappears.

I'm getting the attached codes;

looks like they are pointing to the eccentric shaft sensor...

ph001 · Post by **ph001** » Wed Mar 25, 2020 8:07 pm

What engine?

javis20 · Post by **javis20** » Wed Mar 25, 2020 8:38 pm

Engine is 3.0i N52

I'm going to check to see if there are any oil leaks inside the eccentric shaft sensor plug area tomorrow morning.

javis20 · Post by **javis20** » Thu Mar 26, 2020 5:55 pm

Well looks like the eccentric shaft sensor is leaking..
Maybe I'll do a tutorial..

ph001 · Post by **ph001** » Thu Mar 26, 2020 8:47 pm

Yep, oil on there is not good. Happens a lot on the 2.0 E85, but quite rare on the N52. Tutorial would be great

javis20 · Post by **javis20** » Wed Apr 01, 2020 10:08 pm

Replaced the eccentric shaft sensor and reset the fault codes. Took several test drives and no more fault codes.
However, my problem remains. Still stumbling/hesitating on heavy acceleration. Much worse when cold.

Btw, eccentric shaft sensor and valve cover gasket was a piece of cake on the z4 3.0 n52.

Smartbear · Post by **Smartbear** » Wed Apr 01, 2020 10:17 pm

javis20 wrote: ↑Wed Apr 01, 2020 10:08 pm Replaced the eccentric shaft sensor and reset the fault codes. Took several test drives and no more fault codes.
However, my problem remains. Still stumbling/hesitating on heavy acceleration. Much worse when cold.

Btw, eccentric shaft sensor and valve cover gasket was a piece of cake on the z4 3.0 n52.

How much was the sensor out of interest? I know they used to be expensive

Rob

javis20 · Post by **javis20** » Wed Apr 01, 2020 10:53 pm

I used the VDO. It was $186 from fcpeuro. The job was very easy. Simply remove the one strut tower brace. Disconnect the ignition wire harness, and remove the plug assy from the injectors (leave injectors in place).

I just ordered a few coil packs from Rockauto. I'll start swapping them in and out when the parts arrive. Strongly suspect it's a weak coil pack. Unfortunately it doesn't trow a code. No easy way to find the problem...

ph001 · Post by **ph001** » Thu Apr 02, 2020 6:23 am

Don’t want to state the obvious but assume your spark plugs are all good? Typical symptoms of bad plugs is stuttering on hard acceleration.

javis20 · Post by **javis20** » Thu Apr 02, 2020 1:57 pm

To be honest, I have not. There is only 50k miles on the car. I assume the factory plug is the 4 ground NGK or Bosch. I had those plugs in my VW and they lasted 100k miles. I'll pull a few later and have a look. If I replace them, I'll go with ngk 95712 plugs. I had a problem in the past where the center electrode, on the 4 ground plug, fell into my cylinder. It was fun getting it out...

javis20 · Post by **javis20** » Thu Apr 02, 2020 3:17 pm

Double checked the plugs. Gaps wore open to a tad over .050. Apparently the service interval is 60k miles for the plugs, so I guess I will just order a set, since it need to be done anyway.

Pbondar · Post by **Pbondar** » Thu Apr 02, 2020 6:45 pm

javis20 wrote: ↑Thu Apr 02, 2020 3:17 pm Double checked the plugs. Gaps wore open to a tad over .050. Apparently the service interval is 60k miles for the plugs, so I guess I will just order a set, since it need to be done anyway.

Well that will be interesting..jury’s out?

ph001 · Post by **ph001** » Fri Apr 03, 2020 7:59 am

There is no way I would leave plugs until 60k miles, they are way past their best a long time before that in my experience.

Replaced the ones on my 3.0Si with single electrode iridium ones. Great plugs.

javis20 · Post by **javis20** » Sat Apr 04, 2020 12:07 am

It was the plugs. New eccentric sensor and plugs. Cars running like new again.

ph001 · Post by **ph001** » Sat Apr 04, 2020 12:38 am

Z4-forum.com

Z4-forum.com