muffel moter

[tenntireman]

what would cause a motor to have a muffel down sound, kinda sounds like the exhaust systems is stoped up. I took it to the muffler shop, had him check the Catalytic converter. It was bad so I had the whole system replaced, From the covverter,muffler,pipe all of it. But now it still sound like it is muffel down and does not want to take the gas. I also have replaced spark plugs, spark plug wires,distributor cap and rotor, and ignition coil. I don't know what else to do..

 

[Bill325]

If your exhaust has a heat riser butterfly valve, it could be stuck closed, forcing all of the exhaust from one cylinder bank through the intake manifold exhaust passages. Not all engines still have heat a riser valve. The heat riser valve is found right after the exhaust manifold on one side only, and has a small weight and a spiral spring on it. You probably will not find a heat riser valve next to an oxygen sensor, so look on the other side. Also, be sure your ignition timing is correct, and your ignition timing advance is working. An engine with retarded ignition timing will not accelerate properly. You should be able to see both the initial timing setting and the advance in action using a timing light, and reving up the engine a bit. GM truck engines have had electronic ignition advances since the late 1980s, so you may have to consult a service manual to check the timing advance correctly. On my 1989 Chevy , for instance, I have to disconnect the electronic advance wire to check the initial timing setting. If the timing advances when I reconnect the electronic advance wire, then the advance is considered to be working. Later models may have entirely different systems.