Re: {Chrysler 300} C300 extremely fast idle (1500 RPM est.)

[Justin I <captjj28@xxxxxxxxxxx>]

Hello.  Just to be clear for the group, when you say that you backed the idle screws completely, do you mean just the curb idle screws or did you also change the position of the fast idle screws?  The choke linkage rotates the cam that sets the fast idle via the fast idle screw on the throttle shaft arm.  1500 RPM is the correct fast-idle for a 300B with the similar carb setup.

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From: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx> on behalf of jackcboyle@xxxxxxxxx <jackcboyle@xxxxxxxxx>
Sent: Monday, March 1, 2021 10:41 AM
To: chrysler-300-club-international@xxxxxxxxxxxxxxxx <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} C300 extremely fast idle (1500 RPM est.)

 

I have been trying to self-diagnose the problem for 2 weeks to no avail.

 

History: In 2018, I had the carbs rebuilt by Jim McGowan at the QuadShop.  Prior to that the car ran good but hot starting was a problem. After the carb rebuild car ran perfect. It started hot and cold, it idled, and cruised perfect - but it was past time for wiring and paint. I pulled the engine using a chain around the bare intake manifold and tore the rest of the car down. For 6 months I cleaned, scrubbed, repaired, rewired and restored - getting the car running again and to the paint shop last fall. When I loaded the car to go to the paint shop it idled a little fast but I attributed that to a cold start and only running into the trailer.

 

Two weeks ago the car’s paint was done and went to load it into the trailer. I put 2 gallons of fresh gas and started it. It immediately started idling at 1500 RPM estimated. I had to slam it into gear and headed for the trailer. We aborted because the wheels started spinning on the checker plate ramp. After some scary moments we were able to get into the trailer using the brakes and Ebrake to control the wheel spin. I have not been able to drive the car since installing a new dual MC and disc brakes so the proportioning valve is at the initial setting.

 

Now it sits in the trailer and I am afraid to unload it until I can get the idle down – fearing trans damage or spinning off the ramp. So far I have disconnected the brake vacuum line an plugged the manifold fitting. Removed all the linkages and verified the throttles are shut. Backed the idle screws completely. I see nothing out of the ordinary in the fuel system When I start it up, every time it still races at 1500 RPM.

 

What the hell???

 

 

…Jack

 

 

Jack Boyle

(913) 544 4650

 

Enjoying the same C-300 since 1967

 

 

 

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