I have a '79 Corvette that until recently ran perfectly. When engine first starts, no problems. Car runs great and reacts normally in all driving situations. Engine reaches normal operating temp and stays there. Acceleration, etc is normal with no hesitation at all. Idle is smooth and at approx 800 rpm in Park and drops to about 600 rpm in Drive when stopped. The problem occurs after car has been run for any length of time from 10 minutes to an hour and is shut off for a short time between 5 - 15 minutes. Upon restart, engine idles normally. Pressing on gas pedal gives normal response. When car is placed in gear - either reverse or drive, engine dies.
Restarting after engine dies usually requires some cranking before engine fires. Once started it runs normal again UNTIL put in gear whereupon it dies. If you let engine idle for 10 minutes or so, you usually can shift into gear and car will operate normally again. I have checked all vacuum lines. Carburetor base gasket has been replaced. Fuel filter replaced. Transmission overhauled 400 miles ago. I'm frustrated.

 

Could be a stuck float in the carb (presuming this is a q-jet). You might try a spray carb cleaner into the foat bowl and a couple good raps with a wrench, or light taps with a small hammer to free it up. It can take several repititions to get it unstuck if this is the problem.

At higher idles, this would cause it to run just fine, maybe drip a little overflow from the carb, but nothing major. When under load, or when it senses the idle dropping (like from putting it in gear), it dumps the bowl and floods out. Happens on my boat all the time with nasty aging gas in the 400 gallon tanks.

bill.

 

Bill - thank you. I will try that this afternoon.

 

If that doesn't fix it, try doing a rebuild on the carb. Use a good carb cleaner on the parts while it's disassembled. Contrary to what some folks say, a Q-jet is not all that hard to work on. There's a very good book put out by HP Books on Q-jets also. Let us know how things work out.

 

the cleaner must have done something - as now the car won't accelerate, engine misses and backfires. At idle it runs fine - going to repeat process Sunday. Thanks for help.

 

I agree with 73shark, rebuild the carb and replace base plate gaskets.

 

Rebuild the carb with a new float, make sure you use the specs for the carb number and year of car, try Mike Jones Carbueration aka JET, www.jetchip.com, they used to have everything for Q-Jets.

 

1st, pull the breather and see if you have any pump shot. Make sure your fuel pump isgood, fuel pressure should be 5 to 7lbs. Sounds like you have a fuel supply problem and by looking at accelerator pump shot can possibly determine that. Another quick note, check for spark, a weak coil could cause the problem you are describing.[8D]

 

listen to this man.he,s a wrench for sure.outstanding mech 259