My mother just gave me her car about a month ago. It is a 1992 Volvo 240 with only 138,000 miles. She gave a tuneup and changed brakes, and tires. It drove smoothly until the 2 days ago. As soon as I start the car it start to shake and it doesn't stop shaking even when I am driving or at a complete stop. I pour some of the fuel and carburator cleanser to see if that would work. Everything else seems ok. Can you please help?

Thanks
Chelly

Could be lots of things. Start with the simple stuff. Maybe leaking vacuum hose. When is the last time the fuel filter was changed?

The engine running rough could be caused by a number of things. Do you have normal power or is it sluggish? If it is then you could have a cylinder not firing caused by bad spark plug wires or bad spark plugs. It could also just be a simple vacuum leak. Do you hear any kind of hissing sounds under the hood when the car is running?

I checked the spark plugs and one was pulled off. Once I put it back on and tighten it it doesn't shake. Thanks you guys for giving me some recommendation. I am going to see if it needs new spark plugs.