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

[mr_robot]

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.

[ard]

You posted the same thing earlier..wtf?

[mr_robot]

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

[mr_robot]

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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[Toothbrush]

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.

[Nanniepoo]

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 $$$$

[ard]

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?

[Toothbrush]

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






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.

[mr_robot]

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?

[ard]

Originally Posted by mr_robot

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