81 Camaro running rough, need help!

[sixpack_sid]

My 16 yr old son has an 81 Camaro that has been sitting for a long time. He's been getting it in shape to get it back on the road. When we start it up, it runs fine for about a minute, then idles really rough and seems like it's going to shut off. It's a 305 engine w/carb. We changed plugs, wires, cap, checked vacuum lines. Is there anything else I can look for? He's spent a lot of money to  get it in the shape it is now, I'd hate to see him throw good money after bad trying to fix it.
Thanks!

[greenpigs]

Change all the fuel filters and you may want to pull the carb and at least look to make sure its not gummed up.

[kokxville]

Replace or rebuild the carb.The gaskets are probably dried out.I've had a simular experience with a firebird of a friend of mine.I bought a edelbrock 600cfm the without choke and it ran like it never did before.Besides this carb isn't that expensive too.And like greenpigs said change the fuelfilters and clean the fuellines.
Good luck.

John

[djcarguy]

    remove fuel line from carb,stick it in a plastic bottle and crank it see what you get and how much flow.replace  filters ,blow out fuel lines.suck out gas out of tank and put in fresh. maybe compression ck,were plugs oilly or caked with burnt oil.     tons of stuff to try before ya give up.
  was it a runner before it sat,so much info ya did not tell us.start with the small cheap stuff, before new carb jump and pump more old bad gas in ta new one. i have 2 82 camaros.ck timing,idle setting two low will be shakey and bad coil .and on,on,on     .   al da brest

[Cooter]

Fuel doesn't keep like it used to nowadays. It will go bad in about a month...Also, Slobberjet (Quadrajet) carb's are not known for sitting round any length of time...

[Bobs69]

Replace or rebuild the carb.The gaskets are probably dried out.I've had a simular experience with a firebird of a friend of mine.I bought a edelbrock 600cfm the without choke and it ran like it never did before.Besides this carb isn't that expensive too.And like greenpigs said change the fuelfilters and clean the fuellines.
Good luck.

John

Someone once asked me if my car ran better on rainy days.  The reason being is that the gaskets in the carburator will be swollen up and doing a better job.

[elacruze]

Check fuel pump delivery. If you have gunk in the line from the tank, the pump will fill the carb slowly while shut off but can't bring enough to keep it fed while running. Disconnect the feed line to the pump, let it flow into a container. If it doesn't pour out in a good stream, you'll have to find the blockage. Sometimes blowing air backward will dislodge it (sometimes blowing air backward will blow the pickup sock). If you have good delivery to the pump, check pump output by cranking the engine (ignition disconnected, I use a remote start switch on the solenoid) and checking that the pump maintains a good solid output for 10-15 seconds. If it starts good and weakens, check feed. If it is weak to start, it's the pump.

[nvrbdn]

yep could be fuel flow, could be the gasket under the carb sucking air. once the engine warms and the choke opens it gets too much air. after it warms up try closing the choke part way to see if the idle comes back. if so, change the carb gasket. i used to check them by spraying either at the base of the carb to see if the engine reved.but i wont suggest that since it could grab a spark and make a mess. also if the timing chain is a little stretched, cold it will idle ok, but as it heats up you can loose a degree or two in the timing.

[Hissing Cobra]

Even though you checked the vacuum lines, you may still have a vacuum leak. With the engine running, spray small amounts of carburetor cleaner around the intake manifold. If the idle smooths out, you'll likely find a bad intake gasket. Also spray underneath the carburetor where the gasket is as well. DO NOT SPRAY THE HOT EXHAUST! Make sure all unused vacuum ports are plugged with fresh caps too. Also, if it's like a Ford, make sure that the main vacuum line to the heater box is disconnected under the hood and cap off the port. This will allow you to tell if there's a vacuum leak inside the heater box.

Good luck!

[Bobs69]

yep could be fuel flow, could be the gasket under the carb sucking air. once the engine warms and the choke opens it gets too much air. after it warms up try closing the choke part way to see if the idle comes back. if so, change the carb gasket. i used to check them by spraying either at the base of the carb to see if the engine reved.but i wont suggest that since it could grab a spark and make a mess. also if the timing chain is a little stretched, cold it will idle ok, but as it heats up you can loose a degree or two in the timing.

Is the above quote and what hissing cobra said to do the same as taking a propane torch, not burning, just blowing gas, and pointing it at the intake gasket.  Not sure what its suppose to do...............what does it do?  Raise the idle?

[The70RT]

Stupid question....is the choke pull off working correctly?

[Bobs69]

Stupid question....is the choke pull off working correctly?

What's that?  I know someone that had an 81 with a carb with an electric choke.  Once he grounded it out it went like hell.

[The70RT]

Stupid question....is the choke pull off working correctly?

What's that?  I know someone that had an 81 with a carb with an electric choke.  Once he grounded it out it went like hell.

I know but it was an obvious question and sounds like the typical problem when the pull off sticks or malfunctions. I just figured that was the first thing that was checked?

[nvrbdn]

yep could be fuel flow, could be the gasket under the carb sucking air. once the engine warms and the choke opens it gets too much air. after it warms up try closing the choke part way to see if the idle comes back. if so, change the carb gasket. i used to check them by spraying either at the base of the carb to see if the engine reved.but i wont suggest that since it could grab a spark and make a mess. also if the timing chain is a little stretched, cold it will idle ok, but as it heats up you can loose a degree or two in the timing.

Is the above quote and what hissing cobra said to do the same as taking a propane torch, not burning, just blowing gas, and pointing it at the intake gasket.  Not sure what its suppose to do...............what does it do?  Raise the idle?

yes they are the same. when you shoot carb cleaner or starting fluid at the base of the carb or around the intake, if you hit a leak the engine will rev up showing where the leak is. also will pick up on a vaccum leak with a cracked rubber cap or plug on a vaccum hose outlet. never did it with propane though

[sixpack_sid]

Thanks for all the replies! I will look it over again this weekend and try all the advice!
Thanks again!
Sid

[elacruze]

Stupid question....is the choke pull off working correctly?

Excellent question!

The vacuum pot that pulls the choke open a little right at startup is famous for dying due to alcohol poisoning. When the engine starts you should see the choke plate being cracked open by the vacuum pot, somewhere between 1/8" and 1/4".
While you're in there be sure the electric pulloff works too.
The electric choke is supplied by a fuse, but then runs through an oil pressure switch so it can't pull the choke while the engine is not running. I've seen people pulling their hair out more than once due to a failed oil pressure switch fault in the choke supply circuit.

[Bobs69]

Stupid question....is the choke pull off working correctly?

What's that?  I know someone that had an 81 with a carb with an electric choke.  Once he grounded it out it went like hell.

I know but it was an obvious question and sounds like the typical problem when the pull off sticks or malfunctions. I just figured that was the first thing that was checked?2

No I was being serious when I asked.  Sorry if you took it as me being sarcastic.

[The70RT]

Stupid question....is the choke pull off working correctly?

What's that?  I know someone that had an 81 with a carb with an electric choke.  Once he grounded it out it went like hell.

I know but it was an obvious question and sounds like the typical problem when the pull off sticks or malfunctions. I just figured that was the first thing that was checked?2

No I was being serious when I asked.  Sorry if you took it as me being sarcastic.

No problem Bob, I didn't take it that way at all. Sorry If I sounded sarcastic 

[dodgeboy67]

i had the exact problem with my1980 z28....i replaced the quadrapuke with a small holley( i want to say it was a 450?....but its been like 15 years).....then it went like a raped ape