1997 Ranger 3.0 4x4 5 speed 91000 miles
I know there has been a lot of threads talking about high idle issues. I've read most of them and nothing I have done has found my problem. Intermittent starting issues hot or cold. Loss of power and pinging while going uphill or under a load. Very High revving between shifting. The rpms will go as high as 3500 and hold. This happens hot or cold, dry or damp weather. I've replaced my IAC with a Motorcraft CX1855, replaced the ECM with an updated refurbished Ford ECM, replaced the TPS, replaced the coolant temp switch, replaced the ignition coil as well as plugs and wires. Replaced the EGR tube because of a leak (factory only) and expensive. Replaced the CAT (420 code) and that O2 sensor. Checked for vacuum leaks. Checked and lubed the throttle linkage. Checked and cleaned the throttle body. Checked and cleaned the MAP sensor. My next step is replacing the Vapor purge solenoid as well as both down tube O2 sensors. I may even replace my existing factory spec thermostat with a 180 dergree stat. After the ECM was replaced the truck ran awesome but after a few days here comes the check engine light and all back to running like crap. I also have a slight skip at low idle. Anyone else with some advice before I give in to having it serviced at the dealer will be most appreciated.

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1997 Ranger 3.0 4x4 manual hubs, 5 speed manual, standard cab long bed, 114" wheelbase, 2 wheel abs, tow package, Dana rearend all stock 88,500 mile truck