Stock 81 running rough

boeing46

boeing46

Well-known member
Joined
Jan 10, 2009
Messages
45
Location
southern California
I have a completely stock 81. I have a very bad back so I can't do much anymore. When I get on it it runs perfect. It runs rough at idle.
Could you guys give me a list of what to check.
I am on a very fixed income so I need to do it on the cheap.
It could needs plugs and so on but it acts like a vacuum leak.
 
Rough idle causes:

  • Bad spark plug
  • Bad plug wire
  • Swapped plug wire
  • Bad cap/rotor (shorting in cap)
  • Low compression in one or more cylinders (bad valves and/or rings)
  • Flat cam lobe
  • Bent pushrod
  • Incorrect or bad carb base gasket
  • Leaking vacuum accessory
  • Uncapped port on carb
  • Incorrect set idle mixture screws
  • Leaking intake gasket
just to name a few of the more common.

Lars
 
Thanks Lars,
That was exactly what I was looking for. I will check the things my back will allow me to do. I've read that changing the plug wires on an 81 is very difficult but they look fairly new.
I live near Disneyland in Southern California. The engine was getting pretty greasy and i spayed on some degreaser that was fair at best.
Some of it may have gotten into something.
I am fortunate that there are 2 Corvette speialists- dealers in my area.
I will do the things I'm capable of and if it still runs rough I with take it to one I used before and have a tune up and check for vacuum leaks ect.
I may have gotten some of that degeaser in the air filter. I could get the dealer to do a proper and complete degreasing.
Your the man and answered my question perfectly.
I wish I was capable like most people because i've done 99% of the work on all my cars since i was 15. A back with 5 lbs. of hardware in it limits my capabilities. I miss being a garage rat and customizing my hot rods like I used to. Unfortunatly I can't.
Take care of your back guys because life is hell when you live every day in extreme pain. I can't even change the headlight switch that has the knob missing. I have had some spatacular cars in my day and even won a few trophys at the old RG Canning car shows. I miss it so.
Thaks again lars
 
Boeing, you got my sympathy and empathy both on that bad back thing....no fun, for sure, you ain't alone my friend, lots of us in the same shit boat....

Do what you can, if not, wait till tmrw, or get up at night and piss on it....

:beer::beer::devil:
 
If the engine is running rough, or has a "miss", at idle, you can have someone put the car in "drive" with their foot on the brake while you pull one plug wire at a time briefly off the distributor cap and then re-install it (remove the wire retainer cap and loosen all the wires at the cap before starting this). Whichever plug wire, when removed, has no further detrimental effect on engine idle quality is the offending cylinder, so you can concentrate on that cylinder in your troubleshooting. If the engine idles worse with every one of the plug wires pulled and you cannot identify a single cylinder that is "dead," the problem is likely vacuum related or carb related.

If you do find one cylinder where it makes no difference in idle quality with the wire pulled or not, you can swap the spark plug and wire from that cylinder with that of another good cylinder. If the miss then follows the plug and wire, you have a problem with plugs/wires/ignition. If the miss stays with the cylinder independent of the plug & wire swap, you have a mechanical problem with the cylinder (cam, valves, rings, rockers, pushrods, etc).

Lars
 
Boeing if you washed down your engine and then started the engine soon after you might have shorted one of your plug wires due to the water allowing an easier path to ground. Once the electricity finds this alternate path to ground if the wire is left in the same position it will most likely continue to follow this path. Starting the engine after dark and looking for arching sometimes works. I've heard of guys grounding a piece of wire and running the opposite end up and down the plug wire and looking for the arch.Sometimes just moving the wires around and getting them away from metal will temporarily remove the miss. If you have a heat gun ,shoot each exhaust cylinder and look for a cylinder that is much cooler than the rest.
If you use the method of removing plug wires to look for a miss (considering you have a bad back) don't support yourself with your opposite hand leaning on the air cleaner or anything metal you could get a good shock.
 
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