Zman112233

Hey everyone!

I have a 2006 Cayenne Turbo and when I come to a stop the RPMs dip by about 200 RPM for about a quarter of a second and then bounce right back up. The harder I stop, the more noticeable it is. If I come to a very gradual stop it doesn't do it at all. Most people wouldn't even notice, but I do. Has anyone had this before? Maybe something with the MAF?

Thanks!

dpatel710

Normal behavior. Seems to be worn engine mounts that attribute the most to it.

I changed plugs/coils/gaskets/torque mount/maf seal/etc and didn't see much change. Oddly, when I swapped out the stepper motor for an updated version, it knocked out about half of the vibration when stopping. Its still there but far less noticeable. YMMV.

Dilberto

Motor mounts....ugh

Zman112233

I don't think it has anything to do with the motor mounts because the car doesn't shake or vibrate, the RPMs just dip for a second. I'd guess it was something more to do with mass airflow sensor or cleaning the throttle body.

Anyone had this before?

Kris Murphy

Happens a lot with my 04S. There are certain stop signs where it always happens, which seem to be on hills.

I've had the car for 40,000 miles and it has always done it. I have decided it is normal behavior.

BTW, my motor mounts are new.

provoste

Mine did this until new motor mounts. Now no drop.

bigbuzuki

This sub idle condition seems to plague the 955 series Cayenne’s.

The engine mounts only mask the vibration, they do not cause the idle dip.

Changing the engine mounts will isolate any chassis shudder you may feel when the idle dips.

Mine has done the dip for over 230,000 km. I’ve learnt to live with it.

D!NGO

I know this thread is a few months old but there doesn't seem to be a definitive answer. My 06 Cayenne TTS had the shudder for the last month and I want to share MY experience in case someone google for the "RPM dip coming to a stop" like I did. There could be a number of reasons that can cause this rpm dip as stated above. But for me, there were no engine vibrations while driving or standing still. It was only when coming to a stop does the idle dipped from ~600 to ~400 rpm for a split second and back up to normal again. The engine would shudder a little when the dips happened.

I had checked all the emissions hoses for cracks...sprayed carb cleaner around the intakes..cleaned the throttle body and the MAF sensors(ONLY USE MAF CLEANERS ON MAF SENSORS!). I pried open the oil separator on top of the driver's side engine, cleaned it and made sure it was still good. Each time I tried cleaning a component it seemed to help a little but I think it was more psychological than anything. I was starting to think the dreaded motor mounts was knocking on my door. So I thought what the heck, I unhooked all the emissions hose to checked for broken o-rings and sprayed the inside of the hoses with brake cleaner to get rid of all the gunk....and there was A LOT of gunk judging from how dark the brake cleaner came out...THAT is when I finally found my problem!!!

As it turns out the breather hose was the culprit! It was part# 94810721950 and it sits right next to the throttle body on the driver's side. After cleaning it with brake cleaner, I looked inside and saw that one of the valves was ripped! I had no idea there were valves inside this thing! They should be called Breather "VALVE" instead. I ordered a new one for around $70. Now my car is back to normal again!!!!

So this was my symptom and the fix, yours could be the same or not. But if you have the idle dip, I'd suggest you clean this part first. It would only take 2 minutes to remove this part from your car. There are 2 rubber valves, one on each end and there are very soft and flexible. I just sprayed brake cleaner in each opening and shake it around to clean it. There is a smaller elbow that can be unhook for easier cleaning.

I hope this help someone in the future. I hate it when there's a problem and there are no answers so hopefully this will bring some closure to some.



Here is the location of the breather hose/valve


Inside view with the split valve

david996

fortysixandtwo

Good find D!NGO! I inspected mine tonight and saw tears on both sided of the support. New valve is on order. Hopefully this fixes the shutter.

A Word of caution on using brake cleaner. The diaphragms curled up when I sprayed it. After about 30 minutes they had relaxed back to about their original positions, but it had me worried. The diaphragms are likely silicone, and the brake cleaner I was using has acetone, which silicone does not react well with. I, of course, looked this up after the fact.

The tears are easily visible without cleaning. I figured since I had the part off it was worth cleaning to full inspect it's condition. Cleaning didn't uncover anything, so just skip that step and go directly to replacing it.

dpatel710

vandal968

Great writeup Dingo. Thank you.

cheers,
c

nodoors

Sorry to say I need to present an alternative and negative data point from my own experience.

I replaced the check valve (part# 94810721950) and the AOS on my 05 CTT a year and two weeks ago. They made no difference in the shudder when coming to a stop for me - hot or cold weather, however it did slightly reduce the amount of oil the vehicle burns.

fortysixandtwo

After being lost for 5 days after USPS claimed to have delivered it, my part finally showed up today.

Unfortunately it had no impact on the RPM dip & shudder. Although replacing the valve didn't fix the issue at hand. The old part was obviously no longer functioning as designed, so it still needed to be replaced.

I know I have a cobbled together vacuum T behind the intake, and a split turbo breather, so these may be playing into the issue too. I have a major service coming up, so I'll be repairing known leaks and searching for additional ones. It's very possible this valve is just one of the many components that need to be functioning properly to eliminate the dip & shudder.