I will attempt to keep this brief.
I have a XLS, purchased Certified Used just this last Nov. I am about to bring it back to the dealer for the 5th time for the exact same issue.
When driving usually between 35-50 mph at times an very profound vibration takes over the car. It feels almost identical to driving over groove strips on the side of the highway. It comes on gradually, about 2-3 seconds, then usually goes away after another few seconds.
What I know about the issue (pertinent or not, I couldnt say. I know very little about cars):
1. It is intermittent, not too common. I will feel it at most a few times a week.
2. Going uphill seems to invoke the issue a little more.
3. I can accelerate through it. Usually a little punch of the gas, and it goes away. It seems to only occur when i keep the speed steady, or am very gradually accelerating.
4. Once it occurs, it gradually gets worse. I could be off about this, but it only seems to occur after the car has been on the road for a little bit. I never recall having it happen right after staring it up.
What the dealership has done so far:
1. Suspension (balance, rotated tires)
2. Replaced two front tires (seems to be coming from the front)
3. Replaced front drive axle
After the drive axle was replaced, I went the longest time yet with an issue (at least a month or more). I dont know what else to do. They are throwing darts at this thing, hoping something will stick. I ask 10 different mechanics, have 10 different opinions. I am hoping someone has experience a similar issue.
Thanks in advance for your response.
I will attempt to keep this brief.
Apparently everyone is considering this problem to be related to a chassis vibration. (tires, axle, etc)
My gut feeling is that this problem involves an engine performance issue but there are too many possibilities for me to even start to make a guess at it.
You might consider having someone scan the car for codes. Most chain parts stores such as AutoZone, Checkers, Advance, etc. will do this for you free and it only takes a few minutes.
Keep in mind that an engine performance problem can exist even with no codes. My point is that this problem could be caused by spark plugs, coils, EGR system going a little stupid, vacuum fault, MAF sensor, fuel flow problem (weak pump, clogged filter, etc.).
It’s also possible that this problem could well be related to an axle problem. How many miles on this car? They replaced one axle and if one was suspect the other should be also.
(I would add that sometimes it’s simply not possible to inspect an axle properly while installed in the car. It may need to be removed and checked on the bench.)
To muddy the water even more, this could also be caused by a transmission fluid issue (Automatic I assume) This symptom could match a torque converter shudder. A fluid change may solve a problem like this.
Hope some of that helps anyway.
I agree–as I almost always do–with ok4450.
If I was going to place a bet on what the problem actually is, my money would be on Torque Converter Shudder as the most likely source of the problem, with engine driveability problems being another strong possibility.
There are 2 drive axles, perhaps the other side needs to be replaced too. This kind of problem can occur with a body repair from a front collision. Sometimes the car has a bent frame or is out of alignment and that causes the drive axles and CV joints to wear out prematurely.
I’m sure you have a road where you know you can make this happen all the time on, correct?
Well, next time you are driving on that road, shift the transmission down to 2, and hold the vehicle speed to the same as when it normally occurs. The engine will rev higher, but this is how we can eliminate the engine and transmission from being the cause.
If it still happens with the transmission set to 2, then its a frame/chassis related issue.
I would recommend taking it to a body shop, and have them look for crash related damage.
If it no longer happens when it is in 2, then you are looking at a transmission or engine related issue. Could be as simple as engine mount that went bad, or as complex as a transmission converter that is either failing, or is improperly programmed.