Engine running rough.... help!

[Phoenyx]

OK, so I was driving my Malibu today. I went to pass someone, and I heard a bang from somewhere under the car. After that the car has been running rough. Basically from idle to about 2500-3000 RPMs it shakes the whole car. Feels kinda like I have a big engine with a huge cam.

Anyone know what could have caused this? I don't know if the bang had anything to do with it. We had a big snow storm here a few days ago. So it could have just been a chunk of ice breaking free from under the car.

The only things I can come up with is maybe the carb (I just rebuilt it about a month ago, and it was my first carb rebuild). Or maybe something under the hood got wet that shouldn't have. Or the last thing I thought of is maybe the flywheel cracked or something (maybe that was the big bang?).

If any of you have any ideas, or have had the same thing happen. Let me know.

 

[dan2286]

Does it vibrate when you are driving and parked?

 

[Phoenyx]

Both.

 

[dan2286]

Have you looked at the spark plugs? You might be able to tell if its not running right from looking at them.

 

[Phoenyx]

Well I just looked to make sure all the plug wires were still on tight.

ABout a month ago I replaced the plugs, wires, cap, rotor, coil, and module. So I'm sure that that stuff should be OK ( I hope).

 

[megaladon6]

is the harmonic balancer still aligned?
just in case pull the plugs and make sure that they all look the same. i've seen plugs get fouled inside of 5min so never asume.

 

[85 Cutlass Brougham]

Did you break an engine or trans mount? Could it be a cracked flexplate?

 

[axisg]

is the harmonic balancer still aligned?
just in case pull the plugs and make sure that they all look the same. i've seen plugs get fouled inside of 5min so never asume.

x2. Get some rubber gloves and pull off the plug wires one at a time while the motor is running. You should hear the difference when you pull off a wire. If one ( or more ) does not effect the idle then you have narrowed it down to a plug or wire.

If that's not the problem then you have to look at your driveline ( flexplate, transmount, U-Joint ). I have never seen a flexplate break while driving, only when stressing the driveline ( like a hard launch ).

If you just rebuilt the carb I would hope you put in a fresh fuel filter but it does not take much to plug one up either

 

[Phoenyx]

OMFG...

Well I figured out what the problem was. And thankfully it's an easy fix.

I seem to have lost 2 of the blades off my flex fan (one of those plastic ones). So that's what the bang was lol. Well the fan is probably 5-6 years old. I'm just happy that the blades went down instead of up. The only damage in a small chunk broke off of my fan shroud. Now it's to bad I didn't take the one off of my Bonneville before I had it hauled away.

 

[Blake442]

That's a good reason not to use those!

Find yourself a nice 7 blade fan and put a new fan clutch on it, then you'll be good to go.