car stutters after plug change???????

its a 1990 camaro RS with a 305 (TBI). Everything went fine with the plug change except one rear spark plug was threading off sooo hard that we left it on. Could this one spark plug thats still it its original position be the problem since its old? Car ran fine before tune up. Old wires were used. If i crossed two spark plug wires would it cause this problem or no? It idles and drives to about 30 like its new then it chugs every so often and really chugs hard at around 60 when putting a load(hill) on the car.

SORRY FOR LONG,
Johnny

Could be lots of things. If it runs like a champ at low R's, then it's probably not crossed wires, but it's always good to check. Should be 1-8-4-3-6-5-7-2. The distributor is pretty easy to figure out. The #1 cyllinder post should always point toward the #1 cyllinder... which is the one closest to you on the right if you are looking into the engine compartment from the front end. Then it goes clockwise from there.

Another thing to check is spark gap. I'm not sure the exact specs for a 90 TPI, but I'm sure you can get them online. Also make sure you got the right plug wires. I always go with Accel 8.5's. Nothing compliments a chevy motor like yellow plug wires.

If all that doesn't work, then do a cyllinder compression test. Each cyllinder should pump up around 130-160 PSI for a 350 at least... not sure about the 305, but it can't be too far off. If there is a 10% discrepency between the highest compression cyllinder and the lowest cyllinder, then you're in for a new treat altogether. Can you spell top end rebuild :D

Good luck.

if the car ran fine before the tune up, then i would say its somethign you changed, just intuition. my best guess would be that when you were trying to take off the spark plug, you cracked the porcelin boot, and its grounding into the cylender head or exhaust manifold. also i would double check the fireing order of the plug wires, and check their condition, see if you have a burn through. but my best guess is its the old spark plug, that its damaged in some way and therefore not functioning properly. i would get it out, did you try to get it from the bottom? i always put the car up on a lift, or jackstands, to get to the back plugs from the bottom, MUCH easier. should fix it. that is if there was nothing wrong before the tune up that is.

Check your gaps....

either you have the wires mixed up on the plugs, or one of your plugs is arcing and therefore you are missing. To check for arching, just pop the hood at night and look for blue sparks...