Everyone's favorite topic, engine mounts. I was experiencing some vibration at idle (09 PDK 3.6L), so I asked my Indy to change out the motor mounts, which they said looked ok but had some minor sag in them when pulled. Now my question is the vibration is less, but not really "gone" do the mount have to have some time to seat and soften? They said the Transmission mount seems fine. So my question is can this be something else causing vibration at idle? They cleaned the throttle body and MAF area, the said no faults were thrown in the computer scan of the ECU.

Thanks

 

That doesn't sound unreasonable. You replace the old mounts because they have lost their stiffness, so it makes sense that the new ones would be less compliant.

 

important question: have you done any modifications to the car?

 

no mods so far

 

How many miles on the car?

 

barley 35k, they thought plugs could wait, and the engine looked fine overall, no codes or anything.

 

I personally think that bad motor mounts are an overblown misdiagnosis. I have 100k on my ‘06 and I’m still on my original ones with no sagging or vibration. But that does not help you now. Bad gas could foul the plugs and/or injectors without codes in normal driving. I would suggest emptying the gas tank as much as possible, filling it up with the highest octane gas from a major high volume dealer, put in some fuel injector cleaner, then go for a long highly spirited drive. Fun if nothing else.
if your engine misses in damp and/or wet weather it could be the coils starting to crack. As missing gets more noticeable the codes start showing up.

 

How do you know they aren't sagging? I just pulled my original, 77k mounts. They were definitely sagging, but not leaking yet.

 

Thanks Uwon, I will top off the tank with some techron and give it an italian tune up.

My Indy thought that the plugs could wait until 40k, I doubt the previous owner ever did them, or the coil packs. I would like this vibration to go away for sure, but it's not a crisis

 

one or both tail pipes hang lower.

 

The difference between a new and worn out mount is about 1/4 inch. You can't tell by looking at the tail pipes.

 

Not always the case. When the mount is completely shot and not just worn the motor can drop an inch or more. It's clearly visible at the tail pipes especially in the 997.1's.

OP - check the mount at the other side of the engine, the transmission mount. It has a rubber bushing inside that can go causing vibrations. Not sure how your indy checked it without removing it. The rubber bushing is not visible without removing parts. There's also supposed to be two rubber bushings left and right of the transmission mount sandwiched between the mount and the frame. They are more likely to go with age and weather (hot states more than cold states).

edit: see here https://rennlist.com/forums/997-foru...ear-panel.html

 

Exactly. Your pipes sag if they are SHOT, but that doesn't mean that they aren't worn before you perceive the sag as the poster suggested.

 

Not sure how the Indy verified the trans mount looks ok, semicycler do you need a lift to inspect and remove the trans mount? Are those two bushing visible or are they on the top of the case? it sort of looks like they are at the sides, but might be hard to see?

 

You have to remove the mount to visually inspect it.