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Hello, this started about a week ago. the motor revs great in park and neutral. if i give it gas while driving it has no power and sounds like hell. then put it in park and revs fine. I have to keep it under 2500 or else no power. I am thinking my old q-jet needs to be replaced because it was a concern from the begining. could it be something worse? please help.
Power rods that are in the carb could be stuck in the "down" position, restricting fuel through the jets.
This is not an uncommon problem with todays gas and the quadrajet.
The garbage left behind from today's fuel creats a build up around the piston and it can hang up in the bottom of the bore therefore not lifting up to supply the fuel through the jet as needed.
Vacuum controls the sliding up and down motion when things are right. But if it's stuck in the bore, it will do exactly as you described.
If this is your problem, disassembly, a good soaking, along with attention to the power piston will cure it.
Right on Nitro -
A good rebuild kit may cure your woes. Soaking in a good solvent designed for removing all the yuckies is a must. Not knowing if you're familiar with the Q-jet entrails, here's a couple sketches. Sorry about the quality, but they're copies. I've highlighted the metering rods that nitro referenced with red clouds - they are in pairs (even though shown as a single in the first sketch).
Probably goes without saying - please wear your safety glasses when using the carb cleaner. It can be real hard on the eyes [don't ask..].
Good luck on this
Glenn
thanks for all the info. when i took the air cleaner off this afternoon i noticed that tha vacuum port near the choke had a cracked block off cap. i replaced it and the truck drove home with no issues. hopefully all will be well tomorrow. sometimes i forget to check all the simple things and my mind can only think of the big problems. the diagrams will be very helpful when my other car is up and running and i will have the time to tackle the carb rebuild.
well... I drove it to work this morning and it's back. now i am experiencing carb run on.. guess i will be dealing with it sooner than later. it was wishfull thinking that it would only be a vac leak.