When I started my truck today it began to shake violently. Shut it off immediatly. What could be the cause?

what motor is it?

I don't know. Just wanted to know what reason you could give for the problem.

A little more background info. My son is away for a month. I started his truck once a week and let it idle for a while. After the third week I tried to start it and the shaking occured. It did get colder and I thought this could be the reason. If it was the cold what is happening?

you could just forget about the starting thing? or ask him if it ever did that to him?

I thought you should always start a car once in a while. It never did that to him before. He's had the truck for about three yrs.

it's not a bad idea. did you try giving it more gas to see if it would straten out? afraid of breakin it?

Yes. I felt I would do more dammage if I let it run like that.

when you started it other times, how long did you let it run exactly? long enough for temp to reach normal? that kind of start once and awhile thing can foul the plugs (gas engine) if it's not actually driven. fouled plugs can cause rough/low idle.

I let it idle for about 5 min when I did start it. This last time I started it it was not just a little shakey idle it was a dramatic violent idle. If it is "FOUL THE PLUGS" as you say....what could I do to correct it?

you could take some plugs out and check them for fouling.

Okay.....don't know too much about that. Would I do more damage if I started it the way it is and let it run that way for a while?

you could just leave it alone. wait for his return. me,i would start and give it some gas pedals see if it improves. but hard to judge from here what exactly is goin on.