[msmith8390]

My STS has a strong vibration at idle only!!! The car runs great when first started, until it warms up and idles down. Then I can feel a strong vibration at idle only, if I increase the rpms by just a bit it goes away.
I have already checked for any vacum leaks, replaced intake gaskets, replaced catalytic converters, and I don't think it's the mounts. So I would like to clean EGR valve and maybe IAC,
but I can not find either of these on my car!! All of the info I have found is not applicable to my car, because when I look where others stated it is located it's not there !!!!
PLEASE HELP !!!

 

[kiewee3]

I would bet it's a combination between your motor mounts and transmission mount that are shot. Just my input

 

[dkozloski]

There is no EGR valve. The VVT Northstar achieves exhaust gas recirculation by manipulating exhaust valve timing.

 

[kinggraig]

My car was doing the same thing for months, just took it to cadillac to have them replace the catalytic converters and they told me that I needed to changed my engine mounts. I do my own car work and I changed the mounts this past Sunday and it only took me about 2 hours to change them... It was quite easy besides driver side top nut. Replaced them with revshift mounts and my car is starting smoothly and idling smoothly.

 

[msmith8390]

The only thing that's weird is why when it's ideling higher can't I feel anything ?? Would a motor mount not get worse under higher Roma ?

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I'm sorry Rpm s damn auto correct

 

[kinggraig]

The only thing that's weird is why when it's ideling higher can't I feel anything ?? Would a motor mount not get worse under higher Roma ?

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I'm sorry Rpm s damn auto correct

That's exactly how my car was reacting, I get it idling around 1000 rpm and it started smoothing out. All is cured after I replaced my mounts and when I say the mounts were finished I mean they were destroyed especially the driver side.

 

[msmith8390]

Thanks so much !!! I can tell mine is mostly driver too, when I put my hand on front driver tire, you can really feel the vibration, but not really on passenger

 

[kiewee3]

Kinggraig did you replace the mounts all on your own?

 

[kinggraig]

Yes I just did replaced them Sunday. ...fairly easy job not to difficult besides the driver mount top nut.....space was a bit tight but it's doable

 

[kiewee3]

It doesn't require a lift or anything special?

 

[kinggraig]

I put the car on jack stands....I attacked the driver side first. ....I took the bottom nuts out of both mounts....then I took the top nut off the driver side mount I believe it was a 21mm.....that was the most strenuous task due to the space but it was not that difficult. ....manuals recommend taking off the manifolds I didn't do that. ...they also recommend taking off the brackets of both mounts I just took the bracket off the passenger side due to the manifold being in the way of the top nut. ....so after I took the top nut off the driver side I a regular floor jack and used wood under the engine oil pan to distribute the weight. ...I had one thick piece of wood standing upright on the jack and had a piece of 2x4 laying on top of that thick piece of wood so that I can get the engine high enough without peaking the jack height.....I raised the engine gradually until the driver side bottom bolt was almost cleared from the chassis. ....the passenger side bolt had been cleared. ...I used a flat head to wiggle the driver mount from the heat shield as it was kind of stuck and I replaced that mount and I put that bottom nut back on the driver side mount....I went to the passenger side and removed the bracket 4 15mm bolts with the engine raised those bolts were even easier to get to. ....took the bracket out and with that came the mount I took the top nut off of that mount....that's what holds the mount to the bracket. ....and replaced that mount. .....I put the mount and bracket back in and I lowered the engine making sure that everything lined up. .....went back to the driver side and put that top nut back on the mount and then went to the passenger side and put the bottom nut back on and that was it. .....I read posts on this site and they made it sound pretty difficult but it was actually easy of a job. ..

 

[Neutrocuted]

The only way I knew I had a bad mount was I could feel it when I'd hold the gear shift lever (and in the seat-of-my-pants) when accelerating. The lever would move and I could feel something heavy clunking. I confirmed it by having the OG lightly brake torque it while I watched the engine. You can see the engine jump.

 

[kiewee3]

Thanks for outlining it. I might try and tackle this job myself