I bought this car used. I was told the front engine mount needed to be replaced. When it was replaced, the vibration began. The mechanic used an after market mount. He replaced it with a VW mount and also replaced the two side mounts for the transmission with VW mounts. The vibration was still there. I then took it to a VW dealer and they confirmed that the mounts were installed properly and could not identify the cause. I took it to a third mechanic who made some adjustments to the front mount and that reduced the vibration somewhat. After a few months, the vibration increased and I took the car to another VW dealer. He said the front and side mount needed to be replaced. That was done and still the vibration continued. What else could be going on to cause this problem. Carfax indicated no accidents or body repairs.
Mounts are often blamed for a problem like this but there are other things that can cause it also.
An idle speed that is too low or an engine performance problem are usual suspects.
If the idle speed is what it’s supposed to be then I’d consider an engine performance fault. The first step with performance problems is to run a compression test and make sure there is not a mechanical fault with the engine. One cylinder low on compression can cause a problem like this. Hopefully that’s not the case.
Right now it sounds like the entire crew of people you’ve been going to are wandering around in the woods. At some point someone should give the bad mounts theory up.
Thanks. I will get them to do that.
Yep…OK4450 makes a great point… Your engine shouldnt be vibrating this bad really at all…unless it has an issue… Like a miss. Does the engine run smoothly? or is it “off” a bit… Let us know… THe mounts are there for many reasons but when the engine isnt running correctly…its not the mounts that you need to worry about.
The VW dealership mechanic’s latest guess is the following: The right axle and CV boot were replaced at the same time the engine mounts were done. An after market axle was used. It was not installed properly and the VW mechanic replaced it. When he took the old axle off, the vibration stopped. The mechanic replaced the axle with the same kind of after market part. He is checking to see if the VW axle is hollow. He will know on Monday. If it is, he believes the after market axle, which is solid, may be affecting the harmonics.
Maybe I misinterpreted your original post. I was under the impression the car was vibrating at an idle while stationary. This seems to mean that the vibration is only present while the car is moving.
If that is the case then a faulty axle could cause a vibration problem and it could well be that the reman axle is the cause. I’ve installed a lot of axles over the years with few if any problems but over the last couple of years have seen the quality of remanufactured axles depreciate.
In a nutshell, I think the factories that are rebuilding the axles are cleaning them up, throwing new boots and paint on along with some grease, and calling them good. They fully expect a certain percentage of them to be faulty and returned so it’s budgeted in to the prices they charge.
Before even walking out the door with one anymore I take it out of the box and give it an inspection right on top of the counter. In one case (after a reman axle failure) I found that the next 2 axles ordered were bad right out of the box. The 3rd time, or 4th in this case, was the charm.
(I’m not sold on the harmonics theory at all.)
I do believe that the VW uses a hollow axle…it is rather thick in diameter so this is a further clue… I have an 03 GTi and my axles are pretty fat…fairly certain they are hollow… BUt honestly what diff does it make? It shouldnt vibrate at all…solid or hollow it should be a balance assy. I was also under the impression that you had a vibe without moving…this was what my post wass reflecting anywho… Hope you get it sorted out… I dont know why or how anyone would sub a solid axle in place of a hollow…in any case it should be an identical assy aftermarket or not… perhaps they put on a totally incorrect axle? Again…shouldnt make a diff…as any axle should be balanced.
The vibration occurs when the car is in gear but stopped with my foot on the brake, for example at a red light. At that point, if I shift into neutral, the vibration stops. Sorry for the confusion.
This sounds like we’re back at the original complaint then with the possibiity of an engine performance fault.
If the car is vibrating with your foot on the brake and while the vehicle is stationary at the traffic light then I have no idea in the world why someone would be blaming this on a halfshaft axle except for one reason.
That reason would be the wildly misguided notion on the internet (and it’s been mentioned on this forum before too) about a defective halfshaft causing a rough idle on Subarus. Maybe some of the people involved in your halfshaft swaps have read this bunk and believe it.
What is the idle speed while in neutral and while in gear with your foot on the brake?
If the idle speed is dropping too low with the transmission in gear and your foot applied the engine can vibrate.
The idle speed should be a constant and the ECM should control this by manipulating the Idle Air Control valve. If the idle is dropping too low then the car has a fault in the IAC circuit.
(A vacuum leak in a power brake booster can also cause idle problems when the brake is applied although this is very rare.)
The mechanic reported that when he swapped out the broken, after market right front axle, and before he installed the replacement after market axle, the vibration stopped. When he installed the new after market axle, the vibration resumed. They will install the VW axle tomorrow. He says that, if it continues to vibrate, then the problem is in the engine or transmission. He says that the cost of tracking that down is more than the worth of the car.
Remember that the car started vibrating after the original repairs occurred - engine mounts, right front axle and fuel injectors. As you said earlier, it must be something other than the engine mounts. That would seem to indicate that it could only be the axle or the fuel injectors, right? What else could have happened to cause the vibration to begin right after the repairs?
Thanks again for your help.
The Axle has no businees in the scenario of where you are STOPPED with your foot on brake and engine running…the axle is out of the picture… Now OK4450 makes a great point that there is something wrong with the way the engine is running by itself…sounds like you have a miss for one reason or another…there can be many reasons for this.
Maybe the mechanic moved or disconnected something that affected the engines running ability when he did the mounts or axle? Highly likely
I won’t blame the shop with absolute certainty because it could be a coincidence this problem happened. Coincidences are not a rare thing.
However, I agree with Honda Blackbird that they may have inadvertently dislodged something during the mount changing procedures. Given the number of times they’ve been dinking with the mounts it’s entirely possible. (Vacuum line or broken vacuum nipple maybe?)
The part that dumbfounds me is the bit about thinking a non-rotating halfshaft would have anything to do with a rough idle.
It could be that impression came about because of a Subaru complaint that has taken on a life of its own due to the internet. Someone on this board a few years ago was vehemently positive that a bad halfsaft or worn ring/pinion gear in in the transaxle was causing a rough idle.
This got steered to a Subaru site where some of the resident experts there actually back this crap up. Yep, they ripped me up for saying they were incorrect. 
No one had an answer when I asked why cars running around with near total junk halfshafts idled smooth… 
That argument should have never gotten wind in its sails… Plain and simple. Hate when that sort of thing happens… But it does happen more often than you would think
I am happy to report that the problem is solved. The replacement of the after market axle with the VW axle eliminated the vibration. Thanks to both of you for your help.
Someone is going to have to give me a stone simple explanation of how a non-rotating halfshaft is going to cause an idle vibration while at idle and at a dead stop at a traffic light. Keep it simple or I will never comprehend it.