96 Caviler bucking

[Lonnie.Strunk]

I just wanted to let everyone know what my problem was. I just bought a 96 Cavalier from one owner. I paid $500.00 and new it had some problems.
I have been reading and working on for approx last 2 weeks. Here is what I did. I changed thermostat as was leaking at thermostat. Car has 149,000 miles Cleaned tps. Cel did not come on. New wires, new plugs, oil change because did not know last time changed. My friend has a Snap on Computer we could only find 1 code in computer which said 1406 EGR problem. After reading this forum and many other sites I decided to take off the liner egr valve and clean the carbon out which it did have and the ports also....still had same problem engine would just stall for no reason immertimently and also buck or miss on acceleration. I found out 8 months ago the previous owner had a blown head gasket, valves and head checked a Napa and has had this problem since. In checking connections at engine we found on passenger side 1 motor mound bolt loose we think this allowed engine to move up and down during operation. This may have also cause fuel regulartor line on bottom of fuel regulator nut to work loose has in look it had came unscrewed and dropped down the line. We put back together and this fixed the stalling...no more just shutting down. Still had bucking problem on slight exceleration. I forgot the previous owner had also replace coil module and 2 coil packs. I found on site where a GM tech had similar problem and change EGR valve since only code in computer...this did not fix problem. I did not want to spend 177.00 plus tax to replace just to find out is was not the problem. I also found in same article when a GM dealer can not figure out problem (how can you tell cusomter you replaced 200.00 part plush labor and it did not fix problem) they have another number they call for support or help. The person he spoke with said it sounded like backpressure problems and to check by loosing the clamp before cataylitic converter so back pressure could get out and drive to see if still had same problem.....It did not!
They checked the cat converter and muffler and found cat plugged. So I went with that theory and took to my reputable muffler shop and we checked and changed only the muffler 1st as it was very plugged and cheaper than cat converter. This helped a whole lot but somet time now as much as before did the same thing...I took back next day and had them change the cat converter also. This took care of my problem!!!!Yea!!!
This might help somone else diagonose their problem if simmilar to mine. Looks like a common problem. I am just glad I read a lot and tried this 1st before putting on the egr valve and find it did not solve my problem. and spend another 200.00 to replace muffer and cat converter.
Hope this helps everyone. *Update still have bucking occasionally...I replaced both 02 sensors and not it does not buck anymore. This is what probably helped destroy cat converter and muffler due to running a littel rich* Hope this new info helps !

Lonnie