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redzero

cayenne idle drop engine vibrates when coming to stop

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Without seeing your car in person, just judging from what you're describing it sounds a lot like engine mounts to me. The symptom is a nice deep vibration for one or two seconds from the entire front end as you come to a stop. Its becoming a common issue in higher mileage first gen Cayenne's, say 80K a up but some cars don't exhibit till 100K. If you have corrected the causes of all of your DME faults and you're still getting the vibration/shake when coming to a stop, its almost guaranteed the mounts.

That surprises me as I would expect to see vibrations enter at different engine speeds, etc.

What is the best way to test or diagnose engine mounts definitively?

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Without seeing your car in person, just judging from what you're describing it sounds a lot like engine mounts to me. The symptom is a nice deep vibration for one or two seconds from the entire front end as you come to a stop. Its becoming a common issue in higher mileage first gen Cayenne's, say 80K a up but some cars don't exhibit till 100K. If you have corrected the causes of all of your DME faults and you're still getting the vibration/shake when coming to a stop, its almost guaranteed the mounts.

That surprises me as I would expect to see vibrations enter at different engine speeds, etc.

What is the best way to test or diagnose engine mounts definitively?

The problem with the mounts is that they settle over time. If you take a new mount and set it next to a mount that is "bad" youll see the new mount is about 20mm taller than the used the mount. I believe this allows a part of the engine to touch the body which transfers the noise into the entire vehicle and for some reason it only happens when coming to a stop. Its not like a mount thats torn or cracked and the engine is flopping around which is the usual case with bad engine mounts. The first set of mounts we replaced on a Cayenne was pretty much a complete leap of faith. We had eliminated every other cause we could think of so the mounts were the only logical thing left. After we did the repair we were happily surprised to find the vibration/noise when coming to a stop was corrected because we definitely weren't 100% sure it was gonna fix it before we did the repair. Its at the point now where if I'm driving a higher mileage cayenne and I hear/feel the noise, I dont even need to to look under he car, I know its the mounts.

But to answer your question, is there a definitive test for the mounts? Other than a trained ear? None that I know of. They're almost completely hid by how they sit into the engine carrier so a visual inspection which they're installed is extremely tough.

Edited by PTEC

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Thanks PTEC. This is the same diagnosis as on 928s. The mounts are fluid filled and settle over time. Once the new mounts are in, the engine sits 1" higher in the bay and all harmonics are gone.

I'll have to look into the mounts..... The job sounds very unsavory.

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What's the going rate to have a shop do the motor mounts? Or is this DIY'able?

The procedure to replace the mounts by the book is pretty intense. We support the weight of the engine from the top, on the body. Then we have a special jack that has a huge jig with about 8 different mounting points. These all line up with holes in the subframe and body. Then we loosen and remove the entire front suspension and subframe. With that out of way you can remove the engine carrier and then replace both mounts. After reinstalling all those parts an alignment in required. There may be a quicker way to do it but none that I have tried or heard of. There is basically no room to work around the mounts with the car as it sits normally. They're really weren't designed to be replaced. I'm guessing most shops would charge around 7-8 hours of labor plus an alignment after the repair.

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Based on your description on DIY mount replacement... I guess I'm going to deal with the slight vibration annoyance...

Again, I read elsewhere it could be fuel pump related and/or O2 precats going bad..

I finally had a chance to change out my coils and plugs, minor improvement overall (if any) after replacement (@110k miles). Plugs looked within normal range (color tan/rust to light grey in color) nothing wet or oily burnt nor gas smell at the business end. I did find some oil around a couple of spark plug threads. I was told that there is a slight valve cover leak... may be the culprit

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A/C turned on, no change in idle...

A/C coming to a stop, idle drop and slight vibration, no difference if A/C was

Edited by ALEV8

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I have this dip when I stop as well as after I start the car. It rarely starts on the first try. I have brand new plugs and coils but my battery died after sitting about 2 weeks so it's likely needing replacement. My idle is a bit nervous as well. I'll check my hoses you pointed out. Great thread!

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I'm thinking my idle issue is due to fuel pumps/fuel filter flange/fuel pressure issue related. I'm smelling raw gas on outside rear drivers side which leads me to the flange, pumps etc..

Having Porsche fix as don't feel comfortable around flammable possiblities..

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Resurecting this thread, I had my fuel pumps and flange replaced.. Still having the Idle dip and rumble when coming to a stop.

 

My next fix will be to clean the Throttle Body and replace seal as mentioned earlier.. I will report

 

Has anyone with this issue successfully fixed the problem yet?!

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I have a 2004 TT and also have the vibration. An interesting thing I found was the vibration doesn't happen if I put the car in neutral before coming to a stop. Don't know what that means but is one more piece of the puzzle I guess.

Eric

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I've replaced literally everything. Coils and plugs, both fuel pumps, filter and pressure regulator flanges, all the vac lines running to the booster, even behind the engine cowl and I still have a trembling idle and the vibration while coming to a stop. I'm sitting in the car parked right now typing this and the idle is somewhat rough. I did the throttlebody reset just a bit ago so we'll see how that does. Even with all this work done to the car I'm still not getting 100% reliable starting.

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its the hydraulic Engine mounts

 

they need replacing

 

I learned just to live with it since its not engine drivetrain related

 

I just installed the loudest exhaust system when the idle you wont feel it

 

good luck all

 

keep posting

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YES.

I say reach and replace the mounts!

Somebody can pull this off.

still doesn't explain the burbling idle.....

Edited by ALEV8

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Same here. If put in Neutral, no shudder. Otherwise, just this unpleasant vibration, more pronunciated when engine cold, but otherwise always noticeable. Changed all coils, air filters, reset throttle, no improv. Has anyone fixed it by replacing the motor mounts?

Thanks guys. Mick

CS04, 101k mi

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Just to keep this post resurrected, I recently cleaned my throttle body (you could eat off it now) as well as cleaned both of the MAF sensors and still have the idle dip and then vibration when coming to a stop.

 

Also replaced sparks, coils, both fuel pumps and flange, none has resolved. at 125K on the OD.

 

Loren suspects possible vacuum leak, need to do a smoke test to rule out leak.

 

Interesting that the idle is a bit below, is there a way to adjust the idle up a notch? just a thought

Edited by srfrdrew

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Sorry, there is no way to adjust the idle speed. It is all set electronically these days by the DME.

Fix the leak (or other problem) and the idle will come back to where it should be.

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I had totally the same problem.

So I changed all 8 coils and plugs, MAF sensors, pre-cat O2 sensors,booth fuel pumps, I also cleaned and reset throttle body, and did smoke vacuum leak test, but there was no leaks. All that and Idle drop and rough idle was still there. However, in the end I changed hydraulic engine mounts, and believe it or not, all roughness is gone, and cars is super smooth again. It's PITA job to change it but it's doable and worth every penny. 

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I had totally the same problem.

So I changed all 8 coils and plugs, MAF sensors, pre-cat O2 sensors,booth fuel pumps, I also cleaned and reset throttle body, and did smoke vacuum leak test, but there was no leaks. All that and Idle drop and rough idle was still there. However, in the end I changed hydraulic engine mounts, and believe it or not, all roughness is gone, and cars is super smooth again. It's PITA job to change it but it's doable and worth every penny.

Ok I'm listening.....how'd ya do it?

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Well here is the part.. http://www.ecstuning.com/Porsche-2004-Cayenne-955-Turbo-Sport_Utility-V8_4.5L/ES1441980/

 

Steps to change them out (factory way) - http://www.renntech.org/forums/topic/34911-cayenne-s-motor-mounts/

 

I read somewhere that there is a "easier" way (non-turbo) to change them out, maybe someone else can chime in on that

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Does anybody know a diy vacuum leak test procedure for these trucks? I read about using a party fog machine, cigar, etc. just wondering if anyone's fine it successfully?

How much would it cost done professionally?

The vibration when coming to a stop is way more pronounced when engine cold. Would that be indicative of a vacuum leak? If the mounts are the culprits wouldnt it be the same all the time?

Any input would be highly appreciated. Thanks guys.

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If I EASE to s stop there's barely any shudder if at all....but the shudder upon starting the car when it's cold is very pronounced. My Durametric is not revealing anything though fault code wise!

Edited by ALEV8

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Same here, if I go really gentle on the brakes and have a smooth coming to a halt, there is hardly there. Otherwise, there's always this drop in idle for like a second, accompanied by that annoying shudder. First stop in the morning is just the worst

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