I got an 84 Grand prix with a 231. i just bought the car earlier this month for $150. All it needed was gas and a battery and it started right up. Its having alot of trouble idling but once i start driving it stays running. Can i tune the carb because its computer controlled. ill have pics up soon
My car wont idle. Any suggestions?
- Thread starter Eighty4GP
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I'd start with new spark plugs and a cap/rotor set. Check around for vacuum leaks, like cracked crumbly vacuum hoses. Do all the easy stuff before condeming the carb, you don't want to mess with a ccc carb if you don't need to. If all else fails I once got over by removing the idle screws, squirting carb cleaner in the holes, then readjusting them with a vacuum gauge until it ran smooth. The computer learned to deal with that and it ran quite well from then on.
yeah but the only problem is i dont know what to tune or which screws are which. ive never tuned a carb before. can anybody explain what im supposed to do. i know how everything works, ive just never been taught. thanks alot for the help though.
OK, but you really should get a service manual for the car. Lots of good info and proceedures inside. So, on the front of the carb, at the bottom, are two idle adjustment screws. A ccc carb should be the double "D" type which require a double "D" tool. What you do first is use a tachometer hooked up to the "tach" plug on the distributor to see if the car is at the proper RPM,which is on the emissions sticker on the fan shroud. If there is not a computer controlled idle solenoid then you adjust RPM by a screw on the driver's side of the carb that the throttle linkage rests on. Then you hook up a vacuum gauge to a manifold vacuum source like the one on the carb the air cleaner uses. Then you use the double "D" tool to adjust the idle mixture screws out then in, one at a time,watching the gauge, until you get the highest vacuum reading. Screwing it in too far should cause the motor to slow down and run rough, then quit. Vacuum will drop very low. Do this as many times as it takes to get a good smooth idle. Adjust them to get a high vacuum reading, 20" is ideal. If this changes the idle RPM then you go back to the idle speed screw to adjust it again. What you are trying to do is get the highest possible vacuum reading while staying at the factory specified RPMs. If you find raising the RPM a bit really helps your idle quality, then go ahead and raise it, but not a lot. All this assumes the carb has been worked on at some point and the screws are accessible. If not, and the idle screws are covered with tamper-proof plugs the only way to unplug them is to remove the carb and drive them out. The manual will explain how. I used to think this would cause the computer to go nuts, but actually the computer will adjust to the new settings, if not too drastic. If none of this works then a carb rebuild is in order, and the ccc ones are expensive to get done right. Again, do the easy stuff first-carb last. Hope this helps.
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