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Bad vibrations "95 Buick Century

We got stuck in the mud on a country road yesterday and it took two towtrucks 3 hours to pull us out. The car was dragged with the bottom scraping the high part of the “road” for about 150 feet. I got to the nearest carwash and washed it off underneath as best I could, but the car is shaking and vibrating pretty bad at highway speed.

What damage should I look for? It’s front wheel drive, 124,000 miles. Could something in the steering or alignment be off?


It could be simply mud caked on the back of the wheels throwing them off balance or the suspension is damaged from being dragged down the road.

Put it up on jackstands, remove and clean the wheels, and check the suspension for any visual damage. The pressure washer probably didn’t reach the back of the wheels. If that doesn’t help, take it to a mechanic or alignment shop to get it checked out.

Good luck,

Ed B.

You were right, Ed. All the wheels still had clumps of mud on the inside, front left had mud packed in all around the boots and suspension. I got about half a wheelbarrow of mud from various places underneath. Also bought 3 new tires after getting a good look at their wear patterns. Vibration is gone.

Another question about this car- what causes engine surging at idle? This only happens after driving for 15 miles or more, after the engine reaches operating temp. Idles fine when you first start it up.


Surging at idle normally comes from something like a vacuum leak or a sticky or confused idle air control (IAC) valve. “Parts” that can act like vacuum leaks additionally included a stuck open EGR valve or evaporation system purge valve.

Checking the fuel pressure couldn’t hurt. A new air and fuel filter if they are even close the being due couldn’t hurt either.

Can you tell me where these are located? Is IAC the same as PCV with the hose at front of engine?

No, it is a completely different part.
On the cars with which I am familiar, the IAC is in the air intake passage, between the Mass Airflow Sensor (MAF) and the intake manifold. Yours could be set up differently, however.

Are you sure that you have the automotive expertise for this job?

Any expertise I have is from the old days before all the sensors and computerized controls, so probably not. I’ll take off the air cleaner and look for the IAC. Where are ERG valve and evaporative system purge valve located?

Found a hose with a right angle end dangling from under the throttle body, plugged it back on. Going for a drive now to see if that was it. Thanks for helping me learn what IAC, ERG, and EVAP are all about.