engine shake/muffler
 

can some one help me?
this is what my car is doing-
the engine shakes when it is under 1000 rpm, it back fires 4000 rpm and above, and it has a major loss of horse power.
this is what i checked-
plugs, plug wires, distributor, ignition timing, changed fuel filter.
the muffler broke off and i drove it for 2 days before it starting giving me problems. do i need a muffler on my car, could having no muffler cause it to do that?

when you checked the wires what did you do? did you make sure they are all connected to the right places and are you sure both coils are firing?

how do i know if the coils are firing?

easiest thing to do is make sure the plugs are geting spark. if they get spark then the coils are firing. best way to do that is hook a timing light up to them and if the timeing light works then they are geting spark. otherwise you can unplug all the the spark plug wires. take all the plugs out. put the spark plugs in to the spark plug wires and carefully lay them on the side of the car so that you can see them. unplug your gas line and put a bolt in it. if you don't, when you crank the engine over, you end up with a gassy smoke exiting the spark plug holes. sparks from teh plugs could cause a nasty fire. after all thats done have someone crank the engine over. look for a spark on each plug.

if you both leading plugs don't work, try switching the plugs. if that doesn't help then it most likely your leading coil or you could have a problem with the signal pick up coils inside the distributor. this works visa-versa(if both trailing plugs don't work, switch the plugs...)

the other way to check thecoils is a quick and dangerious way, b/c you could get sparked...IT HURTS, trust me. unplug one coil wire from the distributor and shove a screw driver in the end of wire. set the screw driver so that no part is touching metal except for the handle. make it so that the metal part of the screw driver is close to metal though, so you can see the spark. DO NOT TOUCH THE SCREW DRIVER WHEN CRANKING THE ENGINE.

the first and second ways described will check coils, distributor, signal pick coils, wires, and plugs

the last was checks the coil and the signal pick up coils in the distributor only.

good luck

the coils are firing

anything else i should check

Having no muffler would not do anything, it should run better without it. Check the engine mounts, for the engine to move much when at idle, they are probably very soft/cracked. For the high RPM power loss, if it's a 12a, the carb's secondaries might be stuck closed, check them. If it's a GSL-SE, make sure the 5th and 6th ports are opening.

thanks i'll have check those things out