New Quadrajet stumbles under load and rpms are high with screw backed out?

Question

Put it on 2 days ago, First test drive it worked perfect idle was a little on the high side. on acceleration it will start to stumble and lose power, most of the time. Ignition is not to blame. if i open the choke slightly it idles down perfectly but as soon as throttle is applied it raises back up

Update:

85 c10 305/2wd m4me rochester

pedro7of9 · Accepted Answer

1 check for vacuum leaks,,,base and unit itself,,,any unplugged vac ports
2 if it runs better slightly chocked,,,that indicates to me a lack of fuel,,,check pressure {with gauge,,not guess]
help to have some info on engine,,its not like you pay by the word

mobile mike · Answer

It sounds like whatever style choke heater you have is not working.Some are electric,and some work with a 'choke stove' that's attached to the exhaust crossover in the intake manifold.The high idle is probably from the fast idle cam that's hooked to the choke.Even the secondaries won't open on a Q-jet if the choke is on at all.As far as adjustment gos,I start at 2 turns out on the mixture screws and go from there on a warmed up engine.If you can't fix the choke heater,tie the choke open with a small wire tie and pump the throttle 2-3 times on a cold start.once warmed up it should run just fine.

bandit_60 · Answer

sounds like the choke flap is closing up ! first without it running run the idle mixture screws in until they seat and then run each one out about 1/2 turn, start it and take each screw and run them out 1/4 turn each until you get the best idle ! if the choke is closing up adjust the choke pull-off !

Harry · Answer

the choke needs to be adjusted.

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New Quadrajet stumbles under load and rpms are high with screw backed out?

4 Answers