smparr

My '90 Custom Cruiser has a Y code 307 with a Hot Air Choke E4MC CCC Carb and is having Idle Speed issues. The choke/fast idle will kick off when I tap the accelerator after warm up but it will start speeding back up almost immediately until it is back at fast idle. I can feel it idling fast at red lights and it almost feels like a miss while driving. The engine is fully warm and this even occurs when I park after a 20 mile drive to work, kick it down and it goes back up. Sometimes it will idle down on its own as it warms but most times it does what I just described. Are there any CCC Carb experts out there that could give me a few pointers to look for. I'm thinking a vacuum part or leak but I can't seem to find an obvious one.
things that have been replaced: New transmission, new valve cover gaskets, new rad hoses, new coolant, new oil, no service engine lights.

Any help is greatly appreciated. After this weekend I intend to do a line for line vacuum hose verification.

thanks,
Steve

Sugar Bear

Rule out the choke thermostat by checking to see if the choke blade is wide open when the idle increases. Look at the fast idle cam on the right side of the carb to see if it is on the low step of the cam when the idle is high. Look at the curb idle screw on the left side of the carb to see if the primary throttle plates are closing. Check if the secondary throttle plates are closing. Look at the small green plunger under the accelerator pump lever for sticking downward affecting TPS voltage.

​​​​​If the mechanical checks above are good, have the CCC scanned for codes and focusing on the throttle position sensor voltages. Also the actual engine temp compared with an IR thermometer vs. the coolant sensor reading.

With a CCC carb don't make any adjustments without following the correct factory procedures precisely.

Good luck!!!

smparr

Thanks, I'll try that this week after verifying vacuum lines.