Chevy 454 Problems PLEASE HELP!!!

To test clogged exhaust remove your O2 sensors and drive ( not far this is only for testing) If it makes it past your normal stall point it would be a good guess that the exhaust is clogged.

Are you sure the gas line is not collapsing as the demand for gas increases as you accelerate?

Bad crankshaft sensor

Sounds like in tank fuel pump.can you look down the carb with the breather off when it quits to see if you have fuel spray when you pump the linkage. My 87 had 2 pumps , 1 on block and 1 in tank.

It's an 86 so no crankshaft sensor.

From your description it sounds like you are having a fuel starvation issue. The coach starts up and runs when it's cold but stalls after it warms up. Several things come to mind.

First is routing of your fuel lines. Make sure they're no where near your exhaust manifolds or any heat source. Wrap them if necessary.
Second..are you using rubber fuel lines or steel? Rubber will collapse under hard throttle in certain circumstances.
Third..are you using an electric or manual fuel pump?
Fourth..after it stalls, remove the air cleaner (if its on) and check the butterflies in the carb. Often, after the engine warms up, the spring that holds the butterflies in place is weak and the butterflies will close under throttle. This provides too rich a mixture and will cause the motor to stall. An easy test is to warm the engine, then wire the butterflies open and drive it. See if it stalls. If not, your problem is in the carb.

I don't see it being an exhaust issue as you would experience that without driving the coach.

Try to eliminate the fuel delivery problem. Once that's proven not to be the issue, let us know and we can try some electrical things. My guess is one of the above will be the culprit....with the carb my number one guess....Dennis

Remove the starter and have it load tested at an auto parts store.. Chevys for years have had a problem with engine heat on the starter motor/solenoid and when they go bad you will have a problem as you describe... If it turns over hard after it happens, But starts fine after a half hour or so, I would pull it off and have it checked...

Suburbans of that era would loose both the fuel pump and its relay and cause the starvation symptoms you have. Might be cheap insurance to replace the relay now.

Make sure the fuel pump RELAY is working 100%.

I would bypass the electric pump to eliminate that as a cause. The pump is only there to solve vapor lock issues. Someone removed the electric pump from my '84 in the past and it runs fine without it.

If the pumps are working okay, I would suspect deteriorated lines between the tank and the solid steel fuel line. The pump(s) will lose their prime if there are air leaks. I had this problem on my '84. The generator would run for a while but would eventually run out of gas. The engine eventually wouldn't run at all.

The fuel lines should be easily accessible on the RH frame rail by the tank. A good test is to dip a line into a container of fuel right off of the frame-rail-mounted line. This bypasses the rubber hoses that run atop the tank.

Does it die suddenly like somebody turned off the key (an electrical problem) or sort of "mush out" like fuel starvation or something else?