07 4.8i rocks while in D at idle/stop light
 

Trying to address all drive ability issue before I tackle any other issues and stumped on this problem now.

The best way to describe this is as if you were trying to accelerate a little while in D while holding down your brakes. The car rocks back and forth enough to be noticeable from someone looking from the outside or the if you have a water bottle in the cup holder you can see it move. But it’s very slight movement.

It’s not a vibration or misfire, problem goes away if I put in N at red lights.

I’ve been driving it to see if it triggers a MIL/CEL but nothing for the past few days.

Checked my PCV/CCV on both sides and no milky residue and both diaphragms were good.

I do see my rpm fluctuate up and down from the 500 rpms mark on the tach, maybe 10-20 rpms up/down, maybe a vacuum leak some where? Any thoughts on where I should check next?

It doesn't happen all the time which is frustrating because when trying to diagnose or show someone it doesn't happen.

Thanks in advanced fellas.

You posted the same thing earlier..wtf?

Oops sorry, you're right. Desperate need for help!

So I think it may be brake related?

I noticed if I pull the parking brake switch while still in D it stops the jerking and rpms become steady again as I let go of the pedal.

My brake pedal and braking performance feels fine though.


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That seems strange to me, but maybe someone else has some knowledge here.

It would be good to get some form of troubleshooting tool.

I have OBD Fusion (well worth the $3.99), Carly for BMW with the Carly OBD adapter, INPA and ISTA (though have an issue with this one) and a regular cheap auto parts OBD scanner.

In order of usefulness:

1. ISTA gives much more info and lets you run through a bunch of tests, but can be difficult to set up if you're not comfortable with software -requires a proper cable - Gets you as close to BMW software as you can get
2. INPA is great for quick semi-detailed info, easy to use, little less difficult to install - requires a proper cable - Lots of links/videos online for installing in various systems
3. Carly for BMW (in my opinion) is good, but has too many quirks/limitations - requires an OBD wireless adapter or a cable
4. OBD Fusion [Paid version] is great, if you don't want to spend much money but want to see more than just standard OBD info - can also log and graph - requires an OBD wireless adapter - Note - all of the above can reset many codes/service lights while OBD Fusion is much more limited
5. OBD Fusion [Free version] - meh, better than nothing or standard OBD scanners
6. Generic Auto Parts ODB Scanner

Any one of these can help provide more insight as to what is going on.

Isn't there some sort of issue with oil getting into the vacuum pump? I thought long-term it could cause braking problems, but maybe in this case it's causing a vacuum leak when the brakes are applied?

There's a rebuild kit you can get for the pump O-rings. If you ask BMW (and the indy I went to) the only fix is replacing the pump which is $$$$

OP seems to be "missing" his AC clutch or compressor....

AC Clutch Broken/Missing - Bimmerfest - BMW Forums

Show of hands: Who thinks his idle issues cannot be diagnosed without an AC comp working?

:wow:




At both the 'free' X5 and the rest. Did have a good laugh though.



:popcorn:


mr_robot: hope you listen to ARD, or, at the very least if you decide to tackle this yourself, check the lines for contamination before bolting a new compressor on.

Yea it could definately be the culprit of the missing AC pulley. Just never put two and two together.

Now I'm searching for a compressor. Anyone heard of 4 Seasons?

POS Asian stuff..... you will find it is made by a chinese company, one of many that get the 4s name