92 euro lumina has erratic/pulsating rpms

2 weeks ago, 1 or more cylinders went down. It turned out to be this computer type 'module' that cost me about $300 to replace. The engine was back up and running ok. 2 days later, when I started it, the rpms went way high to about 2200 and within 10 seconds slowly desceded to about the regular 800 or so. Then, as I stopped at the first traffic light, the rpms would, I guess the best way to explain it would be 'pulse', back and forth between 1000 & about 100 rpms trying to stall, till eventually it would stall. The guy who originally fixed it said the catylitic converter was plugged and needed an O2 sensor which he said had to be bought 'together'. He ordered me an new catylic converter and sent it back AFTER he said he had the injectors 'cleaned' and the converter blown clean and replaced 3 sensors he said his scanner showed as defective. It worked great on the way to work. After my shift, I made 3 stops before going home. So far, so good! After I started the car after the '3rd' stop, the rpms returned to advancing all the way up to 2200 or so and slowly descending and then 'pulsating', finally stalling about 3 times. So this problem is obviously not fixed and it's graining my wallett! It has about 120,000 miles on it. Can ANYONE plaease help me? It's been 2 weeks of this steadily now and pulling whatever hair I got left out! Thanks!!!!

I had a similar problem, it ran erratic, plus when it heated up, you could step on the gas, the engine would die(acted like it ran out of gas). Using a scanner, I shot two codes, one being the MAP sensor, the other the oxygen sensor. I replaced the MAP sensor, wasn't the problem. The problem was the electronic ign. module (located in the distributor). When they get weak, they can cause all kinds of problems when they get hot. Its fastened by two screws and has 3 elect. connectors. Take it off, have it tested (auto zone does it for free). Make sure they test it at least 12 times to heat it up. I paid about $24 for mine. FYI, the scanner will not pick this up.

It could be the Ignition Control Module located behind the coils. I figure your repair man replaced the ECM, hidden on passenger side fender underneath fuse panel and next to the coolant reservoir. The ICM gets messed up from heat too, but have coils checked just in case

did he replace the prom(programable read only memory) chip when he changed the computer?? also could be a vacuum leak problem but your mechanic should've noticed if it was. i assume you have a 3.1L these engines are notorious for sucking in the lower intake gaskets. the iac(idle air controller) is another part that might do this. try unhooking the battery for 15 minutes and taking it for a nice long drive. this will reset the computer.