Car shakes violently on startup

[Shadow Conception]

Today, after turning the car on to go to school, I noticed something pretty unusual and pretty damn scary. After I turned the ignition switch to turn the car on, my car SHOOK violently. A spurting, mechanical sound accompanied the violent shaking. I opened my door and got out, leaving the car on; I noticed that my exhaust pipe was also shaking sporadically, and a great amount of similar noise was being emitted from the exhaust pipe.

Wondering if the anomaly would go away if I shifted gears, I shifted into D. There was no effect; my car (an automatic) began idling forward while shaking violently as I let off the brake. I also noticed that my brakes were a LOT weaker than usual; I had to hammer the brake pedal down to stop the car from moving forward. I put the thing back in park.

I resolved to turn the car off and leave it alone for thirty seconds. I then turned it on again. Same result. I turned the car off two more times, and on the final startup, the strange shaking and noise had disappeared, and my car had returned to "normal." I drove to school and just came back. It has been fine since this morning.

I'm at a loss at what this could be. Is this behavior normal? Could it be that the cold weather outside simply required the car a "warming up" period? The car is a 2001 Volvo S60 with ~120,000 miles.

Thanks in advance for any help.

 

[bruceb]

Sounds like a big vacuum leak. Especially since you mentioned brakes needing more pressure. They use vacuum power assistance. Check all the underhood rubber vacuum hoses. Any that are loose or cracked should be replaced. You can spray carb cleaner on each hose. If the idle changes, you have found the bad one.

 

[LTC8K6]

Misfire? Did you see a check engine light?

 

[CoachB]

Sounds like moisture in the injectors/carb or moisture in distributor system. After it warmed a little and evaporated the moisture it will run ok. If it seems to occur in wet conditions or when dew is heavy, you could have a cracked distributor. If it was a vacumm leak, it would not go away most likely.
Warm, moist air from the ground will condense on cool surfaces (car parts) in the fall.

My $.02

 

[basslover1]

There's gotta be an accompanying CEL to go with something like this. If so, head to your local auto parts store and have them scan for the code. It'll probably be a manufacturer fault code, which means they'll likely have no clue, but a simple google search should turn up some info.

 

[MagnusTheBrewer]

Is there blood and fur under your car?

Oh and thanks for the chuckle about rebooting your car as a troubleshooting method.

 

[Bartman39]

Sounds like a big vacuum leak. Especially since you mentioned brakes needing more pressure. They use vacuum power assistance. Check all the underhood rubber vacuum hoses. Any that are loose or cracked should be replaced. You can spray carb cleaner on each hose. If the idle changes, you have found the bad one.

I agree... The brakes are a good clue to a a vacuum issue...

 

[exdeath]

If it's that bad, you need new motor mounts. It won't be the cause of the rough running, but bad mounts will make it worse.

 

[Raduque]

If it's that bad, you need new motor mounts. It won't be the cause of the rough running, but bad mounts will make it worse.

This is what I was thinking. My car has bad motor mounts and when it hits a certain RPM, the whole car rattles pretty badly.

I'd also second a vacuum leak considering the brake effort required. Vacuum leaks don't "go away" though.

 

[LTC8K6]

Running that badly/slowly might mean a lack of vacuum for the power brakes.

 

[Shadow Conception]

I drove the car today again. Put around 50 highway miles on it, round trip from here to near DC. Car was normal the whole way through. Is it magically fine again?

 

[BUTCH1]

I agree... The brakes are a good clue to a a vacuum issue...

Agree X3, if that huge vacuum line cracks or the booster itself develops a leak it would cause a massive vacuum issue. My other thought is a bad plug wire, I had one go bad on a 1.9L escort motor and that motor running on 3 lungs shook the crap out the entire car..

 

[BUTCH1]

I drove the car today again. Put around 50 highway miles on it, round trip from here to near DC. Car was normal the whole way through. Is it magically fine again?

I would look at your ignition wires, when I had my issue it would occasionally arc over to the head and kill that cylinder, usually happened when under heavy load (climbing a steep hill) of if it was damp outside. Might want to get a can of contact cleaner and make sure all of the plug connections are sound..

 

[LTC8K6]

I drove the car today again. Put around 50 highway miles on it, round trip from here to near DC. Car was normal the whole way through. Is it magically fine again?

My bet would be on moisture in the ignition system.

Can't see a bad vacuum leak going away.

 

[Meghan54]

Almost sounds like a plug became fouled then cleared itself enough to fire.

Certainly wasn't a vacuum leak that magically repaired itself.

 

[Jrmill98]

I had roughly the same problem. I came to find out that one of my Distributors was not firing on a piston. It was fairly simple to fix however it was a lot of headache trying to figure out what it was. Hopefully this helps you.

 

[SparkyJJO]

I had roughly the same problem. I came to find out that one of my Distributors was not firing on a piston. It was fairly simple to fix however it was a lot of headache trying to figure out what it was. Hopefully this helps you.

This was 6 years ago, I sure hope he got it figured out by now

 

[MongGrel]

Might be about 6 years late

Hi there.

 

[Pacfanweb]

There's gotta be an accompanying CEL to go with something like this. If so, head to your local auto parts store and have them scan for the code. It'll probably be a manufacturer fault code, which means they'll likely have no clue, but a simple google search should turn up some info.

You would think, but cars act up all the time and leave nary a code.