[KGB_123_99]

Hello folks,

This is actually for an E60 528iX but I figure I would get more views in the E90 forum seeing as it's the same engine. Hoping for some help before I start throwing random parts/money at this.

Recently I'm experiencing the following:

Intermittent stumble/misfire on hot idle. Jolt can be felt in the seat/body.
Does not happen when engine is cold, needs to be driven for at least 15 minutes.
No misfires or stumbles on throttle or when driving around. Pulls at WOT without any hesitation.
Most obvious in Park with A/C off. Less frequent when car is in gear and A/C on.
Car needs to run in Park at idle for 2-3 minutes before the issue occurs.

• All ignition coils changed 3 months ago
• Spark plugs changed 35,000 KM ago (3.5 years), Bosch Platinum
• No codes (ISTA)


Any ideas what would cause this? It definitely feels like a small misfire and I can even hear the occasional fart from the exhaust when it happens but the fact that there are no codes surprises me.

What else could it be: leaky injector, Vanos solenoids, ESS, fuel pump, MAF, 02 sensor? Will take it to an Indy this week but could use advice to point them in the right direction.

Thanks in advance!

[Bmw1939]

How recent? Bad gas?

[KGB_123_99]

Originally Posted by Bmw1939

How recent? Bad gas?

I felt it for the first time last week. I thought it was a one off so didn’t think much about it. Today it has been unseasonably cold and was very obvious.

Last time I filled up at Costco, never had problems with their gas.

A few months ago I had my engine starter replaced at the dealer. I know they took off the intake manifold to get to it but the gasket wasn’t replaced. Could this be causing it or would a vacuum leak always be there and throw a code?

My only solace is that if the car is not throwing a code at least I am probably not causing any damage to the motor.

[Mantraxalos]

Can you check fuel pressure? Perhaps a fuel system cleaner could help. Idle speed is generally increased with the aircon on, so I'm just thinking something with the fuel. I believe a code would be triggered if there was an air leak as the air is measured after the MAF. I'm sure we have many more members that know much more than me though.

[oVeRdOsE.]

I had somewhat the same issue few weeks ago, here what I did , all in same time, so pick the one that fixes my issue.

- new PCV valve (15$ and 1.5h )
- Cleaned coils pack, cyl 5 got oil in it from previous old gasket (0$ and 10 min)
- Cleaned both vanos solenoid, BOTH were jammed ( 0$ and 45 min)


Pretty sure the issue was the vanos solenoid, but freaking strange that the car was super fine, and the day after BOTH jammed. I've tested both on 12v battery, and none moved. Carb clean + wd40 and they are fine,.

if you got the starter changed, you might have a hose leak, those plastic hoses break only by looking at them, broke mine while disconnecting it from the back of the engine.

You can also unplug the MAF to see the behaviour while hot.

[KGB_123_99]

Originally Posted by oVeRdOsE.

I had somewhat the same issue few weeks ago, here what I did , all in same time, so pick the one that fixes my issue.

- new PCV valve (15$ and 1.5h )
- Cleaned coils pack, cyl 5 got oil in it from previous old gasket (0$ and 10 min)
- Cleaned both vanos solenoid, BOTH were jammed ( 0$ and 45 min)


Pretty sure the issue was the vanos solenoid, but freaking strange that the car was super fine, and the day after BOTH jammed. I've tested both on 12v battery, and none moved. Carb clean + wd40 and they are fine,.

if you got the starter changed, you might have a hose leak, those plastic hoses break only by looking at them, broke mine while disconnecting it from the back of the engine.

You can also unplug the MAF to see the behaviour while hot.

Thanks for the tips. My PCV was built-in to the valve cover and I had that replaced last year along with PCV hoses so they shouldn't be that brittle yet. I will try changing the spark plugs (cheap) and will ask the shop to look at the VANOS solenoids. The coils are very new and usually those exhibit issues under load in my experience.

I unplugged the MAF, but the car started running like crap so it was impossible to tell what's happening.

What drives me nuts is the idle problem is not there all the time. It takes 2-3 minutes of idling at a long red light before it starts happening. I'm leaning toward a leaky injector at this point. Maybe the fuel starts accumulating and messing up the ignition.

[KGB_123_99]

Originally Posted by Mantraxalos

Can you check fuel pressure? Perhaps a fuel system cleaner could help. Idle speed is generally increased with the aircon on, so I'm just thinking something with the fuel. I believe a code would be triggered if there was an air leak as the air is measured after the MAF. I'm sure we have many more members that know much more than me though.

I will ask the shop to check the pressure. Wouldn't fuel pump issues exhibit themselves across the RPM range?

[oVeRdOsE.]

best shops for bmw:

-eurozone
- stancedub
- momentum

by the mean time you can do that, and apparently you can calibrate them too, I didnt have to do the calibration tho

[KGB_123_99]

Originally Posted by oVeRdOsE.

best shops for bmw:

-eurozone
- stancedub
- momentum

by the mean time you can do that, and apparently you can calibrate them too, I didnt have to do the calibration tho

Thanks for the shop list. I've always had good luck with RPM but will try these other ones if RPM can't solve it.

I've had VANOS solenoid issues before but in my experience they always threw a code and the rough idle was there all the time, very consistent.

[KGB_123_99]

So after further experimenting today, the idle stumbles only when the car is in Park or Neutral. If the car is in gear, everything is fine no matter how long I stay stopped.

Going to the shop tomorrow, hopefully they can figure it out.

[oVeRdOsE.]

Originally Posted by KGB_123_99

So after further experimenting today, the idle stumbles only when the car is in Park or Neutral. If the car is in gear, everything is fine no matter how long I stay stopped.

Going to the shop tomorrow, hopefully they can figure it out.

that means you need to swap for a 6mt

[Glene]

Check to see if the PCV holds Vacuum. If it does not hold vacuum, then it can cause the problem without setting codes.

[KGB_123_99]

So the issue turned out to be…(drum roll)…spark plugs. The gap on 2 out of 6 was too big. Now she is purring smoothly again with 6 new plugs.

Now what is strange is that these Bosch Platinum plugs only have 40,000 km on them. I didn’t check the gap when installing but they do come pre gapped. I wonder if this is bad luck, knockoff plugs (Amazon) or something else.

Regardless just happy that it was a relatively inexpensive fix even with shop hours.