1992 S-10 4.3 Vortec TBI. Having problems. Truck started stumbling and idles fast. would not pull hill and bogs down when given full throttle. Pulled plugs and most were fouled. We put in new plugs, wires, cap and rotor button and still had same problem. Thinking it was the coil we put on a new one and had same problem. So we checked EGR Valve and was working properly so we pulled the Cat Converter and still had the same problem. Service engine light came on and had code for O2 Sensor so put on new one. Fired it up and was missing like crazy, let it idle awhile and it smoothed out and ran fine but idled a little fast. Went for test drive and still misfires at full throttle and engine light came on again for O2 Sensor. Pulled IAC Valve and was clean and set at proper length. Also Fuel Pump and filter was replaced last year. Don't know what else to check. Any help would be great

 

The O2 sensor is looking for back pressure from the cat, reinstall it. Missing isn't a coil or usually ignition as that either works or dosen't. Plugs fouled? Oil, or fuel, thats the key to troubleshooting your issue.

 

Thanks Kevin,Is it because it's a 92 model that requires the Cat installed to work properly. Just curious because I had a 95 S-10 with same engine and the Cat was removed for awhile until new one ordered came in and it worked fine with no code. Yes the plugs were fouled, mixture of gas and oil on them but the cap was in such bad shape plugs couldn't fire if they wanted to. Would O-2 Sensor be the cause of not being able to take full throttle and also idle fast. Thought MAP Sensor was cause of fast idle but checked values with ohm meter and it shows good and also reason I replaced the coil was because readings were weak on it as well.