I was wondering if anyone has had this simular problem. I have a 89 with the Renix MPI on a 4.0L. When the engine is not at operating temp(open loop) the truck runs great, but once it is at op temp (closed loop)the problems begin. If the engine is brought above 900-1000 RPM, whether by the gas pedel or by coasting in gear the enine starts to miss and back fire, finally bogging down until under 1000 rpm again. It still idles great however. I have check the speed sensor, the O2 sensor, the TPS, replaced the MAP sensor and checked the sync sensor (cam position sensor)in the distributor. if you have any sugestions please let me know.

Thanks

I had similar problems. Try here (http://www.automotiveforums.com/vbulletin/showthread.php?t=253756)

I have tested the EGR valve and the EGR solinoid and everything checks out......Thanks though