I need some help troubleshooting a rough idle problem with my daughter's Valiant. It is a stock 225 with a Carter BBS. I have added electronic ignition to it some time ago. I pulled the plugs this morning, and all are the same- very light with a small amount of tan.
The symptoms are that it will run fine above about 1500 RPM, but as soon as it comes back down to idle, it will stumble, cough, and often die. The problem is worse when it's cold. I have to constantly feather the throttle to keep it running. It seems like it is experiencing a lean condition but I can't find a vacuum leak. Also, when it gets hot, it boils fuel over onto the intake manifold.
Here is what I have done so far:
1) Replace distributor and ECU (several weeks ago, it refused to start, and it turns out the pickup in the distributor was bad).
2) Set timing to 5 degrees BTDC at idle with vacuum advance unplugged
3) Disassembled and cleaned carburetor several times. Float is at 1/4". All other adjustments made per rebuild kit.
4) Adjusted valve lash to 0.010" Intake, 0.020" Exhaust
5) Checked plug wires for leaks/shorts
6) Checked coil per spec
I'm stuck. I've been working on newer cars for a while now, and think I've forgotten how to tune the old schools!
The symptoms are that it will run fine above about 1500 RPM, but as soon as it comes back down to idle, it will stumble, cough, and often die. The problem is worse when it's cold. I have to constantly feather the throttle to keep it running. It seems like it is experiencing a lean condition but I can't find a vacuum leak. Also, when it gets hot, it boils fuel over onto the intake manifold.
Here is what I have done so far:
1) Replace distributor and ECU (several weeks ago, it refused to start, and it turns out the pickup in the distributor was bad).
2) Set timing to 5 degrees BTDC at idle with vacuum advance unplugged
3) Disassembled and cleaned carburetor several times. Float is at 1/4". All other adjustments made per rebuild kit.
4) Adjusted valve lash to 0.010" Intake, 0.020" Exhaust
5) Checked plug wires for leaks/shorts
6) Checked coil per spec
I'm stuck. I've been working on newer cars for a while now, and think I've forgotten how to tune the old schools!