Ercoupe idle problems

[HillBilly]

This is my first time on a forum so be gentle. I recently completed an annual on a 1947 Ercoupe 415C and did the after engine run only to find that after 10 minutes or so the engine would not idle. It would hunt from 600 to 1000 rpm. I attempted to advance the throttle and the engine response was very sluggish, about 20 seconds to spin back up to max rpm. I can run at max and move the throttle with good response but then it will suddenly react as explained above. Troubleshooting I did: recheck the fuel system to include all filters, fuel lines for clogs, all with no problems noted. Fuel pressure maintains a 2 psi throughout the entire time. There is also an electric pump installed which makes no difference, on or off. I removed the Stromberg WA-S3A1 and rebuilt with no effect. Recheck mag timing, checks good, does any one have any suggestions for me?

Thanks for the help,
HillBilly

 

[GravityHater]

feel the butterfly with your fingers and make sure it is not loose.
look at the induction pipes for leaks, do a leak test with soapy water and the back side of a shop vac blowing where the carb was removed.
overhaul the carb

 

[Waldom]

Had similar symtoms with a Continental A-65. Turned out to be loose intake rubbers on both cylinder and intake spider ends of intake tubes.