Why is my engine shaking?

FATAF25

MEMBER
2004 CHEVROLET TRAILBLAZER
135,225 MILES

My trailblazer shakes when I sit idle at a stop sign or red light or parked, but it acts completely normal when I start to accelerate. It drives fine until I slow down to stop then the rough shaking starts. I'm worried it will soon die on me and I have to have a vehicle. What is it, can I fix it, and will this cost me a fortune? Please help.

Wednesday, March 14th, 2012 AT 3:09 PM

7 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

This sounds like a low compression problem, Lets start by doing the test that way we don't chase your tail.

Here is a guide to help us get started

https://www.2carpros.com/articles/how-to-test-engine-compression

This guide may help as well in case you have a vacuum leak.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please let us know what happens.

Cheers

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Wednesday, March 14th, 2012 AT 3:47 PM

DBOOGIE

MEMBER
3 POSTS

I found the engine has low compression in #4. I guess its time for a valve job. Thanks for your help on this one guys!

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Thursday, May 3rd, 2012 AT 6:13 PM

CANDLELINA

MEMBER
1 POST

I have same issue and the check engine light does not come on I have changed the ignition coils all 6 and spark plugs the fan clutch water pump motor mounts I am at a loss. No one can figure it out until I read this thread. Thanks guys

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Thursday, November 29th, 2012 AT 3:21 AM

CHAGY14

MEMBER
2 POSTS
2005 CHEVROLET TRAILBLAZER
4.2L
6 CYL
AUTOMATIC
158,000 MILES

Ok. So im driving down the road and all of a sudden the engine light comes on and the engine starts to shake. Almost immediately after the engine starts to sound like someone is beatong on the inside with a hammer. Its really bad and really loud. But when I accelerate to about 30mph its not as loud but still sounds horrible like its about to blown up or like there is some metal stick in the fan just spinning around inside. Im scared to drive it anywhere.I aaked someone to look at it and they said that they thi.K it needs another motor. Im kind of tight for cash and dont really want to have to do that but if I have to I guess I will. But is there anything elae that would cause this. Or anything that I could be able to tell if thats exactly whats wrong. Could it be something else

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Friday, September 22nd, 2017 AT 2:10 PM (Merged)

CARADIODOC

MECHANIC
34,330 POSTS

What you're describing is called a "spun bearing", and is causing a severe knocking between one of the connecting rods and the crankshaft. If you had stopped the engine immediately the repair could have possibly involved a new crankshaft, and a set of engine bearings, but due to the loss of oil pressure the pistons would have been scuffing on the cylinder walls too. That damage takes place within five or ten seconds. That's why you're supposed to stop the engine right away and coast to the side of the road. To keep driving does so much more damage that it requires a complete engine rebuild, or a used engine that you hope doesn't do the same thing.

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Friday, September 22nd, 2017 AT 2:10 PM (Merged)

CHAGY14

MEMBER
2 POSTS

Someone told me it might just be the fan clutch. Is this so? What can I look for to tell me the difference?

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Friday, September 22nd, 2017 AT 2:10 PM (Merged)

CARADIODOC

MECHANIC
34,330 POSTS

Fan clutches can cause shaking but they will not cause the Check Engine light to turn on. By the time they get bad enough to make a lot of noise they will be wobbling so badly that they'll tear up the radiator and you'll have a massive coolant leak. You can check the fan clutch by just grabbing the fan blade and wiggling it to see if there's any movement. Do that with the engine not running.

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Friday, September 22nd, 2017 AT 2:10 PM (Merged)