72 Cutlass - rough idle - no acceleration

tomeeg · 10-12-2016, 07:37 AM

I have a 1972 Cutlass with the 350 Rocket engine that was in a parade on the 4th of July, so idled through a 2 mile parade route, and then ran rough after the parade. Engine idled rough and would not accelerate promptly. I drove it to work after the parade day, and it ran fine, but when I left work, I stopped at idle for 3 minutes talking to another employee and it then ran rough and when I tried to rev up the engine, it backfired and just ran rough.

I replaced cap and rotor, plugs and wires, fuel filter and installed a refurbished carb - and still the same problems.

Any recommendation on what to do next with it?

Tom E

tomeeg · 10-12-2016, 07:39 AM

Just another note, but when it idled for several minutes and died, I had plugs 1 and 2 removed to see if it was flooded and there was no fuel in these cylinders. I did replace the fuel pump as well, and could see fuel was going into the carb but it's odd that it still ran rough and there was no fuel in these cylinders.

maxwedge · 10-12-2016, 05:24 PM

Lot of things can cause this, stock ignition I assume. Look down the carb when this happens, see if is dumping fuel at idle. A bad coil can fail when hot. Can't really diagnose this online.

tomeeg · 10-12-2016, 07:29 PM

I realize this isn't an easy scenario, but was hoping to get some ideas on what to check on this issue. My mechanic friend is looking at it, but he is more accustomed to working on the newer vehicles, so not sure what experience he has in the older generation vehicles.

He did check the carb and saw that fuel was going into the carb, but after it ran for a couple minutes and died, he took out the plugs to see if it was flooded and they were dry, so he is baffled over what to inspect. We're going to replace the float, seat and needle, but not sure if that's going to fix it or not. Since a rebuilt carb was installed and it ran the same way, I can't imagine it's a carb issue, so not sure where to turn to next.

Thanks for your response and I will keep all updated on what is found with this vehicle (assuming it gets resolved)!

tomeeg · 10-12-2016, 07:31 PM

I also meant to say everything is still stock in this vehicle and it has around 119k miles on it. I put around 14k miles on it since I bought it 20 years ago, so curious if it's time to rebuild the engine (even though I don't see any unusual smoke coming out of the exist which points towards the need to rebuild).

maxwedge · 10-12-2016, 07:41 PM

Make sure the small filter in the carb inlet fitting is not plugged.

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