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

I had similar problems with a WCFB but it never worked right once (even initially ) after rebuild by Daytona carb . forget them , really— instead of rebushing worn front throttle shaft on passenger side they wrapped thin brass shim stock around old shaft (!!) . It later moved an edge ( a corner) of that shim stock into throttle bore and held throttle disc slightly open . So idle stop screw was not working / touching once throttle disc touched the shim obstruction in the bore. = Could not reduce idle , and it took a very heavy spring , seemed to open itself under vacuum , confusing . Sounds easy now, drove me nuts then . You could not see this visually . Rebuilt the carb again myself fixed it , found mangled shim ( that idea does NOT work) put bushing in. There is a kit on ebay , with reamer , excellent , about 40$

Look at how many turns in , on another carb, are showing when on idle screw , —at idle — compare to yours . That should tell you plates are closing tight = nothing bent or something . Carbs were off when lifting ? Chain bend anything ??? I have seen the choke high idle linkage arm on the spring side of carb that pivots on secondary shaft slightly bent in toward the carb body in a way that causes it to hang up , hits anothe part of linkage only near throttle closed , subtle thing to find . Looks intended to be that way , it is not . I think very careful look at pictures in FSM helped find that , those pieces are confusing but all are parallel to carb flange .

Better to use tabs under manifold bolts with tiltable spreader / lifter worth every cent in angling engine in and out without hurting things.

Vacuum gauge might help you too .

While people are thinking carbs ,I have a ram that backfires consistently on one side AFB carb when cracked open just off idle , only on one side , 300J type deal, accell pump is fine . Engine perfect compression and leak down , idle perfect . (whew— thought bad or tight intake valve) Never saw that before .

Thoughts? Like you — problem came up after long sitting elsewhere trying to get it out of moving truck . Of course. Nose to tail with valuable Mercedes. And wanting to jump . Took out by 4 guys pushing .

Sent from my iPhone not by choice

On 1 Mar 2021, at 3:01 pm, Ray Jones <1970hurst@xxxxxxxxx> wrote:

Hi Jack;
Let's go back to this sentence in your description:
I pulled the engine using a chain around the bare intake manifold and tore the rest of the car down.
This is a heavy and you were swinging it around by the manifold to head connection. Likely you distorted the manifold and have a leak at that connection.

If you have a propane torch, do not light it but with the engine idling, turn the gas on slowly and start going around the manifold ports @ the heads. If the idle speeds up, you found the air leak which is the most likely reason for the increased idle.
Let us know, Ray

On Mon, Mar 1, 2021 at 9:41 AM <jackcboyle@xxxxxxxxx> wrote:
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???

<image004.jpg>

…Jack

Jack Boyle
(913) 544 4650

Enjoying the same C-300 since 1967
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