75 CDV hard starting when hot

[jaydog]

My car has 27K on it and when driving, it runs perfectly.  In the last couple of months, this issue started: (The Quadrajet was rebuilt at 24K and performed flawlessly until recently).
Even though the choke is set properly, after sitting a couple days I have to crank and pump to get the fuel moving.  Hi idle doesn't seem to kick in anymore, so no reason to tap down. After the car gets hot (not overheated hot, operating temperature hot) and I park it it will start right up again. However, if it sits for 30 mins or more and I turn the key, it starts, then stumbles and stops running.  I have to crank it for a bit, then it starts again and runs fine except, say at a stop light, it idles smooth, then stumbles a bit like a miss.  Thought the starting issue may be a float too high and flooding out.  My mechanic took the carb off, cleaned it again and put a new float in...same problem exists.  I ordered new plugs AC R45XLS6 and new AC wires just to be sure (even though the plugs have only a few thousand miles on them) to eliminate that as the problem.  I know I set the plug gap properly when I put the plugs in (which were Champion RN16YC5's).  I have not pulled the plugs yet, waiting for the new ones to arrive first.  Timing is at 6 degrees....I can't think of anything else except maybe a vacuum leak to cause the idle stumble, but I don't think it would affect the starting and, again, runs perfectly when driving.

Suggestions appreciated.

[TJ Hopland]

Did the high idle get fixed when the mechanic did the other work?

What kind of time period did this last 3000 miles get put on in?

[jaydog]

4k miles since Sept 18..no issue til recently. Don't know about the hi idle cam.. Have to run it back to him.

[MeToo]

Could it be the idle speed needs adjusting? A failing fuel pump?

[Jon S]

Before you go crazy the ethanol laden gas is probably the culprit.

[jaydog]

That's what my mechanic, who used to work for Cadillac as a mechanic in the 70's, says...bad gas.  I did put in some Lucas ethanol treatment, I'll see how it goes.