High Idle, No shifting after new carb gasket

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Catalina Kirill

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Another day, Another issue.. As the title suggest, after I changed the carb gasket (because it was leaking) my stock 400 with TH400 trans and stock quadrajet idles way to high, and best of all. Won't shift any further then first.. Before i took the carb off, everything was fine. Fine idle RPM, and shifter like butter. Except it was a little shaky because of the broken gasket. Whilst in there, i changed the spark plugs. Thats it. I even left most hoses on it and just let the carb dangle of a wire mounted to the hood when changing the gasket.

I took the carb back off to check if any valves are stuck, but everything seems just fine.. What is happening here?

Greetings from the Netherlands!
 
It won't shift because something happened to the vacuum hose going to the transmission modulator which will also cause a high idle because of a vacuum leak.
 
Allright, so I checked the trans mod hose and indeed, it wasn't attached to the modulator at the trans.. I only checked the carb side. So, that's fixed! Still runs quite high at idle..

Could it be a happier engine and i just need to tune down the idle screws? or likely something else still unhappy?
 
Assuming it's a Quadrajet is the choke fully open?
Is the throttle adjustment screw on the drivers side touching the throttle stop?
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Did a full re-check on all vacuum hoses. Choke is fully open and throttle adjustment isn't touching. Still running high idle (around 1000 rpm). It's a good, no hesitation rpm. Don't know where to look anymore..
 
Catalina Kirill said:
Did a full re-check on all vacuum hoses. Choke is fully open and throttle adjustment isn't touching. Still running high idle (around 1000 rpm). It's a good, no hesitation rpm. Don't know where to look anymore..
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Look on passenger side, fast idle cam in choke linkage maybe stuck.
 
Sorry, what I mean by the screw not touching the throttle stop is that I screwed it all the way out till the throttle stop is actually touching the metal where the screw goes in.
 
Catalina Kirill said:
Sorry, what I mean by the screw not touching the throttle stop is that I screwed it all the way out till the throttle stop is actually touching the metal where the screw goes in.
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Ok I ment was the end of the scew thread touching the stop. Either way move to the other side and check the fast idle cam. Again I'm assuming you have the factory Quadrajet.
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Got ya. Will check tomorrow! But to be sure, the fast idle screw at the passenger side will move the throttle a bit right? So if engaged there's a gap between the throttle stop and screw.

Yes, factory qjet
 
Yes if the fast idle cam is stuck there will be a gap between the drivers side throttle screw end and the stop.
 
Are you sure you used the correct gasket?
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Perhaps the carburetor throttle blades are hitting the gasket for some reason. Only so many things cause this problem, vacuum leak, throttle blade obstruction, linkage obstruction such as fast idle cam.
 
Finally found the issue. Don't know why but i pushed in the green pin on passenger side (don't know what it's for. Secondaries blade??) and down the rpm's went. Spins like normal again!
WhatsApp Image 2024-03-28 at 23.14.05.jpeg
 
Catalina Kirill said:
Finally found the issue. Don't know why but i pushed in the green pin on passenger side (don't know what it's for. Secondaries blade??) and down the rpm's went. Spins like normal again!
View attachment 7173
Click to expand...
Excellent, glad you found it
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