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I have a 2000 DTS; I have been experiencing - what I refer to as a rough idle. Two visits to the Caddy dealer resulted in them doing a diagnostic check (telling me no codes) and a cleaned throttle housing.

I'm no mechanic (obviously) however, when I open the hood, I find the engine to be "shuddering", consistent with what I feel while in my car. I guess what I'm asking is, Could this be the result of a bad motor mount - thereby causing the engine to shake, reverberating throughout the car? If so, why didn't the dealer take notice?

Thanks in advance.
 

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bobstoc said:
I have a 2000 DTS; I have been experiencing - what I refer to as a rough idle. Two visits to the Caddy dealer resulted in them doing a diagnostic check (telling me no codes) and a cleaned throttle housing.

I'm no mechanic (obviously) however, when I open the hood, I find the engine to be "shuddering", consistent with what I feel while in my car. I guess what I'm asking is, Could this be the result of a bad motor mount - thereby causing the engine to shake, reverberating throughout the car? If so, why didn't the dealer take notice?

Thanks in advance.
It's probably the way it's running that's making the engine shake.
 

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Do they make a Helms manual for the current generation DeVilles?

If so, I'd recommend getting one, finding the idle adjustment screw, and cranking it up by maybe 50-100 rpms just to see if the vibration goes away. Then back it off until just before it starts again.

Then again, maybe the Caddy doesn't have a screw like that. I don't know, never cracked one open before.
 

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In 1998, cadillac took away one of the upper truss mounts to make for a more "comfortable" idle among other changes in 98. This did in fact put more stress on the main "front" mount but make the car idle a bit better at the sacrifice. If you hot rod the car, you are going to brake the front engine mount, especially in a 98 and newer. Its actually a pretty easy thing to change is you have a good jack and are handy with tools, but its one of those things that the dealer will overlook every time as no one pushes these cars hard enough to make an issue of this. The same goes for 4.9 liter FWD car with over 60K, they more than likely have a broken mount. The easy way to tell if yours is broken is to; start the car, open the hood, put the car in drive, give it a little throttle against the brakes and it that engine lifts up more than about an inch, you got a broken one. If you hot rod the car, put a new mount in the strap the engine down with aircraft cable... Again not hard to do and there is no sacrifice of anything should you do this.

bobstoc said:
I have a 2000 DTS; I have been experiencing - what I refer to as a rough idle. Two visits to the Caddy dealer resulted in them doing a diagnostic check (telling me no codes) and a cleaned throttle housing.

I'm no mechanic (obviously) however, when I open the hood, I find the engine to be "shuddering", consistent with what I feel while in my car. I guess what I'm asking is, Could this be the result of a bad motor mount - thereby causing the engine to shake, reverberating throughout the car? If so, why didn't the dealer take notice?

Thanks in advance.
 

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Personally, I WOULD NOT recommend changing the idle screw...... I did it on my car, and it made matters worse....... TRUST ME!!!!

You need to figure out what the problem is.... I dont know if cadillac has anything like this, but there is a test called a POWER BALANCE TEST, which individually tests each cylinder and reports how many RPMs each cylinder made the engine go down...... All should be within something like 15rpm........ All this is done by a computer you hook up to the car (a TechII)......

I dont think its a motor mount, after only 2 years..... normally those will last the warranty period.......

Sounds kinda like a lazy dealer...... Id go to the next nearest one and see what they can come up with...... its also good to get second opinions.......!
 

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I know this is late but....i had the same problem and mine turned out to be the motor mount. i havent replaced it yet. you said it was easy to do? i had it looked at b y my mechanic and he said there is a special tool you need to replace that or something. can anybdoy give me directions on how to replace this. thanks
 

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I guarantee you that the pistons are off timing. Guarantee, Floor the motor a couple times, and run it fast, and let the engine come down. THats the only solution i see. No motor mount would run down that fast, unless you floor it all the time.
 

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yeah i did floor it a lot. not anymore.... but i read on another thread to give it gas against the brakes in drive. if the motor rises...... well my rose a lot. so anybody have directions on this? or do i have to have cadillac do it? or some motor shop that has the right tools? thanks
 

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devillain00 said:
yeah i did floor it a lot. not anymore.... but i read on another thread to give it gas against the brakes in drive. if the motor rises...... well my rose a lot. so anybody have directions on this? or do i have to have cadillac do it? or some motor shop that has the right tools? thanks
i had a rough idle i thought at first in my 1990 deville but it turned out to be the front motor mount and a front transmission mount, now it's smooth as a button.
 

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> guarantee you that the pistons are off timing. Guarantee, Floor the motor a >couple times, and run it fast, and let the engine come down. THats the only >solution i see. No motor mount would run down that fast, unless you floor it all >the time.[/QUOTE]
Short of a broken crankshaft there is no way for the pistons to get off timing. Your valve timing could be off if the drive belt/chain (not sure which the op's car has) but that is usually very evident in lost performance and serious idle problems.

Sometimes when you have a bad motor mount you feel the "clunk" if you accelerate heavily from a dead stop. As another poser suggested I would try another dealer. It sounds to me like your dealer just doesn't want to be bothered with the problem.

Steve B.
 
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