My 1993 3.0L V6 2WD Ranger is running rough on the road, but not too bad at idle. I first thought it was related to the transmission because I recently had a Torque Converter lock-up (diagnosed by Ford) that mysteriously fixed itself before they could determine the root cause. But I checked the EEC codes yesterday and got a KOEO 335 (EGR feedback signal out of range) and a KOER 326 (Pressure Feedback EGR shows low pressure EGR not seating). Will an EGR problem cause the vehicle to run rough? Should I take the shotgun approach and replace the EGR valve, or are there additional diagnostic steps I should take? Could this be a problem with the EGR Vacuum Regulator as well, or the PCM?
I have never tried to trouble-shoot an EGR system, so any practical advice would be appreciated. I do have the Haynes Repair Manual for 1993-2000 Ranger pick-ups.
I would try removing the EGR valve and cleaning the pintle area out before starting to replace parts. The EGR's tend to get clogged up with carbon and then start sticking. Also check the EGR valve for a ruptured diaphram. You can simply suck on the vacuum hose going to it and see if it will hold vacuum. Also check all of the vacuum lines going from the EGR to the engine, for a leak.