Shaking engine at Idle/Park

Hello everyone. I have a 1992 Chevrolet Corsica LT 3.1 V6 with approx 224,300 miles on it. A few months ago I felt the car shaking when I was at a red light. I thought nothing of it [because it stopped.] Just recently, it has started doing this again. I have opened the hood and watch the actual engine shake back and fourth as the car is in park.

I am not sure what is causing this issue. I had to take the car to a mechanic three days ago. [Smoke came out of my hood and all the coolant poured out of my car]

The mechanics replaced the water pump, thermostat, radiator cap, oxygen sensor, fuel filter, transmission fluid, and coolant. The car drives well, but still shakes.

Does anyone know what could be causing this? Could it be old age and high mileage?

Ithink you might have a bad motor mount or maybe a transmission mount.

Really? I have to add that I DID have the motor mounts replaced about a year ago. When I bought the car, I would hear rattling whenever I went over a bump or pothole - but since the replacement of the mounts - no problem.

But a transmission mount huh? Never thought of that. Would that be expensive to replace? Can you actually see a bad mount?

Also, when I had issues with the motor mounts, my car wouldn’t go over 30 MPH - it was pretty bad.

Yes, the problem could be the result of bad motor mounts and/or transmission mounts, but if the motor mounts were replaced about a year ago, that leads to another question, namely–How well is this engine maintained?

As just one example of what I am referring to, if it is running with really old spark plugs/plug wires, and/or if the fuel system is really gummed up, it is possible that this situation results in a very rough idle and that the really rough idle is laying waste to the motor mounts. This is just something to consider.

However, if I were you, I would be more concerned about, “Smoke came out of my hood and all the coolant poured out of my car”. Depending upon how far/how long the car was driven while it was overheating (you undoubtedly saw steam, rather than smoke), there could be serious damage to the engine.

Truthfully, a car that has been in service for 18 years, and has traveled over 200k miles has little life left in it. Are you sure that you want to continue to spend money on repairing a car that is only going to keep needing more repairs at a steadily increasing rate?

Thanks for your reply. I’ve been taking good care of the car, I’ve had it for two years and I am the second owner. I don’t know the former owner at all. :[
The original owner had traded the car in and I found the Corsica and bought it. I had my Dad look at it before the purchase [he knows a little about cars].
[The Corsica was the best car we found and was all I could afford - I am a college student after all]

Yes, it was steam, and I was told that the thermostat was not working properly, which contributed to the issue. The coolant actually came out of the overflow tank and drained under the car.

I guess you are right! I really love my car though - Maybe I should save some money for a “newer” one. It saddens me because I’ve put so much money into already. :[

Also, you said the spark plugs may be to blame, huh? Maybe I should get another tune up.

When were they last replaced, in terms of odometer mileage?
If it has been more than…let’s say…20k miles, then they are probably due.

Uh . . . I was told the previous owner did it before they traded it in. :[

Ummm…You do realize that people rarely do maintenance on cars just before they sell or trade them, don’t you? You do realize that used car salesmen will say virtually anything in order to sell a car, don’t you?

Even if the previous owner did replace them just before trading it in, they are at least 2 years old.

In reality, those spark plugs are…God only knows how old.
Replace them, along with the plug wires and you will likely have a much smoother-running engine.

You’re right. Hopefully this will help my car. Do you recommend a certain type of spark plug for my car?

Just my opinion, but a vehicle that has a history of smoke, coolant overflow, cooling system parts replacement, and a likely overheating episode should have had a compression test run before any parts were replaced.

This will weed out low cylinder compression on one or more cylinders due to the overheating.
If compression is down on even one cylinder the engine will vibrate and there is no cure other than engine repair. The engine may also smooth out when revved off of idle.

Thanks. I wonder how much that would cost!

A compression test is a simple procedure and a preliminary test to this could be the use of a vacuum gauge. A vac. gauge can be connected in seconds and will show instantly if there is a problem that needs a closer look; as in compression test.

It’s also possible that this vibration could be caused by a vacuum leak, which the gauge will also reveal. A vacuum leak could be due to a faulty intake manifold gasket, cracked vacuum line, etc. and the 3.1 engines have had a few issues with intake manifold gaskets anyway.

Again, and just my opinion, a few things should be headed off at the pass when dealing with a problem like this. The comp. test to weed out a mechanical engine fault and considering the shop has done a lot of work with the cooling system it’s incumbent upon them to not just replace parts but to make sure there’s not an issue when the work is done.

The Six Spark Plugs Must Be Removed To Perform A Compression Test. Should The Engine “Pass” With Sufficient Compression, New Plugs Can Be Installed Instead Of The Old Ones.

If it doesn’t pass then you’re probably looking at a lot more than just spark plugs and you’ll have to decide if it’s worth it to save the car.

I recommend using the spark plugs specified by Chevrolet, the car’s manufacturer. Auto Parts stores have this information.


Hi everyone. THANK YOU SO MUCH for all your advice. :]

VDCdriver, you were right! I had a mechanic take a look at it and test drive it [they said it was the spark plugs and wires] and had those replaced - and my car no longer shakes!!! I’ll be sure to tune my baby up from now on! :]