Few problems with my 94 Caprice

I just bought a 1994 Chevrolet Caprice (4.3L), and Im havin a few problems with it. My first one is that the warning light for low coolant comes on SOMETIMES when I start the car, and then it goes off after a about 20 seconds. Other times it doesnt come on. I checked my coolant, and it looks like I have enough. Does anyone know why it might be doing this?

Also, it seems like the car is idling a little rough. It hasnt been driven in a while. But when Im sitting at a light, the car rumbles and shakes a little, and when Im driving down the highway and Im not accelerating, it shakes a little. But when I accelerate, it seems fine. What things should I look at to fix this problem?

Can anyone help me?

Also, what type of gas should I be filling up in this Caprice? (It is a 4.3L)

The coolant level sensor is located in the expansion tank. You can drain the coolant, remove the tank, remove the sensor, and clean it or replace it. Since you just got the vehicle, a cooling system flush and refill may not be a bad idea anyway, unless you have reliable maintenance records that indicate it has been done in the past two years. If it's been three years, it's time. If it had been switched to DexCool, you may get a couple more years out of it.

Your other option is to disconnect the switch.

As for the rough running, the fact that it accelerates with no problems would tend to indicate that the Opti distributor is working without problems. You may want to remove plugs and inspect them, test the wires, and update the fuel and air filters.

Your car should be able to use even 87 octane regular unleaded, with or without 10% ethanol. The PCM will monitor detonation and adjust timing as necessary to prevent any damage and maintain best mileage. You may want to get a fresh load of fuel anyway, since old (low volatility) fuel may be part of the rough running problem.

Oh ok, thanks. I was planning on replacing the plugs and wires soon, so hopefully that will fix the problem.

Also, I hear this slight rattling or knocking noise comming from the back of the car when I let it idle, but it goes away when I accelerate. (The noise actually is at the same time I feel the car idling rough). Do you know what could be causing this?

Someone told me that it could be a bad catalytic converter or my muffler.

The car has about 129,000 on it..Im hoping to have this car last for a long time, cuz its my favorite car..even if that means getting a whole new engine and tranny when they go out lol

The rattle could be a cat letting loose internally, or something as simple as interference between the exhaust system and the body. I have a feeling it is being compounded by the fact that the engine is not idling smoothly, and may "disappear" once you solve that issue.

If you are going to change the plug wires on an L99/LT1, plan on spending several hours, and raising the vehicle to gain access to the terminals at the distributor. They are packed in relatively tightly, and are nearly impossible to access from above. Cylinders #4 and 6 are especially "fun" since they are at the top of the Opti cap on the right side.

Oh ok. Yea, I actually just looked at the car..I had it running, and I looked under it. I saw that part of the exhaust system looks like it is shaking, and rattling up against the car from what I could see. Im not a big genious on cars, so I'll have one of my friends look at it for me also.

The last problem Im having is, I filled up antifreeze yesterday to the "Fill Cold" line, and now I looked at it today and it is back below the line again. I dont see the antifreeze leaking anywhere, and there was no spots on the ground. Any suggestions on this?

Pull off the radiator cap with the engine cold and see if you can see coolant in the radiator close to the top. If you can then put the cap back on and start it and very slowly loosen the cap to see if the system is under pressure and be ready to quickly tighten it back if it is. If you can't see coolant then start the engine and add coolant to the radiator until it stays close to the cap and let it run for a while to get out all the bubbles in the system, then cap it off and fill the resivoir tank to where it should be. Might just be that there's alot of trapped air in the system which keeps emptying the overflow tank and also resulting in the low coolant light coming on.