Cutlass455

I have a 72 cutlass with a 455 in it. It's a rebuilt motor, it seems to run good. When I start it, it idles kind of bad, sometimes might snub out. But when it is warmed up. It still has power, but if you hold the gas at a steady pace you can really feel the misfire. Any suggestions?

ryneves

Take it to a mechanic and have a compression test done. See if timing is correct. If you aren't a mechanic it's best to take it to one and have the problem diagnosed. It could be one of a multitude of things from timing to carburetor issues to fuel pump issues to fuel line issues to fuel filter.

RandyS

Have you checked to see if all of the plug wires are on tight? If they are, try removing one at a time (then hook it back up) until you find the one that has no effect on how the motor is running, that is the problem cylinder. May be a bad wire or a bad plug, or ??????????????????????

illumined

Maybe a vacuum leak? If it's big enough that might cause it to stall on idle. There's quite a number of things that can do this too unfortunately.

oldcutlass

It might help if you tell us what ignition system, carb, cam, compression, etc... Also what your tuneup settings and vacuum readings are.

toymobile

Check firing order 5 and 7 are so easy to cross it's not funny. Good luck'

Johnny

MDchanic

A noticeable miss in steady driving, with idle problems, points pretty strongly toward the ignition system, and most likely to a bad cap, wire, or plug (though nothing else is absolutely excluded), so pulling plugs to see which one doesn't change the engine speed (and doesn't change the driving performance) is very reasonable.

Hooking it up to a SUN machine would be even better, but good luck finding one nowadays.

Good luck!

- Eric

m371961

Pull and examine the plugs one by one. Look for the one that looks different from the rest. If you pull the wires while running it is easier to loosen them first with engine not running.

64Rocket

Does it have a "pertronic" conversion?

If so, check the magnetic ring under the rotor. I had one lose a magnet and did the same. Had a miss but still ran ok, but a miss.

Gene

Cutlass455

I ended up changing the timing and now have another problem! It runs amazing at idle, now when I had it, the throttle is not responsive at all, and when I get about halfway to the floor, it then decides to have power but seems like it's not getting gas and keeps bogging down, it gets jerky and then goes, but the throttle was very responsive and went right when I put it down, anybody have a clue?