I have a 94 camrey with a 4 cylinder it is running really rough, it only runs smooth if I put it in neutral, but if I turn the a.c. on it will run rough. Ive read alot of post that are similar but not quite as bad. any help would b great, thanks

Take an have diagnostics run . Could be a vacuum leak , mass air flow sensor problem , If fuel injector's where the problem it wouldn't smooth out while accelerating > Have fuel trims check , O2sensors . EGR valve stuck open a little . If the check engine light was on an had a random misfire code P0300 could be fuel injector. or a specific cylinder misfire.

Depends on what you mean by rough. Could be a cylinder misfire.They sometimes are not noticed as engine speed increases during driving or under light load as when idling in neutral but at idle under load as when stopped at a light in drive became noticable.
Could also be running rich. The causes of either are too numurous to list.Consult a good mechanic who can actually see and hear the problem to put you on the right track.

Power is reduced, oil when the engine has a stuffy as small hammer knock. Serious damage the crankshaft and connecting rod, and even lead to piston broken, hurt the body and the cylinder head. Recommended maintenance as soon as possible.more go hobd2

Run some injector cleaner through the system.

vacum leak find fix

Clogged or Damaged FreshAir Intake Hose.

you should check a throttle body valve or purge valve, choke valve

have your control module tested first if its okay then you may have a coil pack thats acting up .good luck.

1st to do,replace fuel and air filter, spark plugs.

seem like you got the same problem as my scion xa, check the fuel pressure regulater. bad regulater some time smell like leak gas. auto zone might cause you about $80.00.