Whats wrong with my truck?

94 chevy 4by4 213000 miles on it...well the exhaust is making this claping sound. every eight ten secounds...umm th rpm guage moves up and down when in idle but not to bad if you look at it bawbles back and forth evrtytime it does this the truck moves like its about to die but then it kicks back up.again its not that bad when it does it..more of a nudge..well my friends say the alternator may be going bad..i although it was because when I turned on my wipers the nudge inhanced...we adjusted the timing but it like set its self back..wird?.maybe it may be the distributer.. the whole thing?..what so yall think is wrong with my truck?..

Check and see if all yer plug wires are tight. Sounds like electrical problem to me too.

Go to a parts store and let them read the codes I think it could be more of some sensor and you have to set the timing properly.

sounds like its misfire you need complete tune up 1st

check the compression to see if you level across all cyclinders this may be a valve problem with sound you talk about but with this many miles it may be various causes, you don't point to wheather you have had any big repairs in the past and if you haven't you're due for any number of things as well as a complete rebuild.

I hope you have been doing maintenance on this truck. Have the plugs ever been changed? Take it to an auto parts store and have them read the codes and see if it'll tell you where the problem is. It can be something simple, but it's annoying.

The clapping sound and the rpm swaying is most likely being caused by a misfiring cylinder.

Sounds like the a/c is on and is fast cycling because of a low charge and also the idle air control valve is sluggish and not rising the idle fast enough when the compressor kicks in.
Turn the a/c off and see if it still has the problem. If replace the IAC valve and have the a/c recharged.