1993 explorer problems

I have a 93 explorer and it will run fine for a while, but then the tach will start jumping and going to zero and it will start dogging out real bad. If you step down on the accelorator it will come out of it. But it goes right back doing it. The code told me about the coil pack. I replaced it and it is still doing it. Sometimes worse. Got any suggestions?

I have the same problem. At stop lights I have to keep my toe on the brake and my heel on the gas to keep from stalling.

I tried cleaning the throttle body. No joy. I checked the computer codes and it said the mass airflow sensor was bad, so I replaced it. No joy. Next I replaced the PCV valve and idle air controller. No joy ...and No joy. I triple checked all the vacuum hoses, connections and caps. Still no change. I'm pretty well stumped.

I'm going to check the oxygen sensor today. Apparently, when it starts to go the engine's computer can't sense the oxygen levels to adjust the fuel-air mix, so it has to go off previously stored readings which might explain the dogging in idle. I'll let you know how it goes.

loose ground wire somewhere