Originally Posted by shane.vattimo
Alright folks here it goes. cylinder 4 on gmc jimmy has a bit of a misfire and a slight of a rough idle. hesitation bog down when i stomp the accelerator. its a 99. spider injector is fine, we have a bright blue arc off plug and new plug wires. i have put a hose from even side of motor to ear and it is one of the smoothest motors i ever heard, not tick knock ping or chatter. how much does anyone know about back pressure affecting cylinder 4 misfire, on that side of the motor there is a small dent in exhaust pipe before the "y". please help...this piece has consumed my weekends for to long as i work a lot and have 2 small kids and a home renovation going on. wits end folks. somebody save me.
Start with the simple and clean your throttle body and your AMF sensor. With a dirty AMF sensor, it can cause the issues your describing and would not hurt also to give your engine a http://www.seafoamsales.com/
Good luck and keep us posted.