: '89 Brougham, 307 "Y" . Really FAST Idle.

12-03-09, 02:38 AM
This Caddie has 116,000 miles on the OD. Just bought it 4 months ago. Owned one a few years back and I know they all have their quirks. I Can't slow the idle speed down . Engine is warm, Choke is wide open, fast idle cam is not stuck. Still revs around 1,500. Read many posts about the Idle Load Comp. valve on side of carb. The only way I can slow it down is remove the ILC and put a stronger return spring on it, back off idle adj. screw all the way. Still idles around 900 (runs on, disels) Checked for vacumn leaks with carb spray at base of carb and intake. Any ideas ?'''' Thank You.

12-03-09, 11:01 AM
Are you 100% sure there are no vacuum leaks?

12-03-09, 05:21 PM
Have you disconnected the throttle cable to verify its not holding the throttle partially open? A vacuum leak on a carb'd car will NOT cause a fast idle, only a very rough idle. The idle load compensator is mainly there to raise the idle with A/C on or extend out as you decelerate to prevent stalling. Are the secondaries possibly stuck partially open? is the secondary air flap behind the choke blade fully shut?

12-03-09, 06:51 PM
The throttle linkage would be the most common cause for your problem, but the carburettor could also cause an improper idle speed. If it is flooding or the float level is out of range, then it would be increasing the idle. Check the float level if you have an external float gauge.

Another thing that could cause improper idle speed is the ECM. The 307 carburettor is semi-computer controlled. My service manual suggests to check the engine idle speed, both base and ECM controlled, as stated on the emissions label.

12-05-09, 06:27 PM
Thanks for your suggestions, gonna take another stab at this problem this weekend.

12-05-09, 08:55 PM
FIXED...! Throttle linkage pointed me in the right direction. It seems the the rod going to the cruise control had been shortened up. All I had to do was move the cotter pin to a different hole in the the rod end that connects to the cruise control. Idles smooth as silk like an old Caddie should! Thanks again for the help. Allways the simple things.....