Engine Vibration

[sroney]

Good evening, and Happy Thanksgiving to everyone.

I have a 2000LS that has a vibration on acceleration. It is evident at all speeds, but it is very pronounced at around 30MPH and moderate throttle. I know that this is not much to go on, but any ideas would be appreciated.

[Iflylow]

Only on acceleration? If not, check wheel balance.
Could be a misfire also, how old are your spark plugs and wires?

[sroney]

Yes, it is only on acceleration. It feels like it is in the drive train. The plugs and wires are fairly new. And it has the same feel after the new plugs were installed as it did before.

I didn't know if motor mounts could be the issue?

But it is not a tire balance issue.

[don_t]

I am having the exact same problem..I was told it needed a tune up. I did that, not any better. I just put new tires on and had them checked twice. The more people that are in the car, the worst the vibration. Thanks for any help with this..

[57chevyragtop]

There is a few different things that can cause vibration on acceleration. 1st I would look at the plugs and wires even if they are fairly new. It only takes one bad plug or wire for this. 2nd. there has been an issue with the engine aluminum cradle welds on some units and should be thoroughly checked (TSB calls for replacement if I remember right) I would also look at lower motor mounts and loose fasteners where the cradle fastens. Also state which engine you have please?

[1996Chreokee]

how many miles? did you ever service the transmission? is it a transmission shudder?

[Iflylow]

sroney has a 3.8. The LS only came with the 3.8. Check all motor mount bushings for sure.

[don_t]

I have an Impala LS with 3.8
I had the transmission serviced too.
Took it back and since they could not find a problem with the wires or front end suspension, they told me it was my transmission. I am thinking about going to a transmission shop next.

[don_t]

I have 163,000 miles on my LS

[sroney]

I actually have 146K mikes. I had been told that the transmission was bad, and needed replaced (due to hard shifting, not this vibration) but I had thought that maybe it was a transmission issue.

Now the tranny is replaced and I still have the vibration. But, that is the kind of feel it has, which is why I thought possibly a motor mount type problem.

How difficult is it to check the cradle, motor mounts, etc? Or is that something I should take it to a shop to have checked?

And yes, it does have the 3.8L

[57chevyragtop]

It really depends on your mechanical abilities. If you feel comfortable getting under the car on jack stands and inspecting the mounts and cradle. If you have access to TSB's you may want to look for that or go to the dealer and see if they will look it up for you. I think it deals with a faulty weld on one of the corners of the cradle, it has been a couple of years since I read it. I no longer have access to them. May want to use leverage "carefully" to see if you have any loose points that show movement or breakage. Also if you have AllData you can look up TSB's there....Autozone used to have them but last I checked they were no longer available online.

[don_t]

sroney, when they replaced your transmission, did they replace the transmission mounts? I had someone that seemed to have the same problem get them replaced and the vibration went away..

[sroney]

I'm not sure, but my guess would be that, no, the transmission mounts were not replaced.

[SpinnerCee]

A clogged CAT will cause the symptoms you describe as well -- it will appear that all kinds of things are going wrong with the engine and tranny (PCM codes are not likely to be indicated) -- here the issue is excessive exhaust back pressure that shows itself most prevalently under load -- an exhaust back-pressure test will quickly rule this out.

[don_t]

I did have my CAT replaced 6 months ago..I was told it was an after market CAT..I suppose I might need to go back to the man that put it on for me..Thank you..