Surging Idle on 93 Ranger
 

At a little loss for where to investigate next for my buddies 93 Ranger. So far we have replaced the Idle air control, plugs and wires, cleaned the mass air flow. New thermostat, fuel filter and B/S. He is having a very erratic idle speed. Upon initial start up the idle will spike pretty high b4 relaxing a bit, then while driving it will sometimes surge similar to when idle air control goes bad. I also hear a strange noise from the EGR assembly sounds like an internal rattle in valve when you goose the throttle. Is this normal? No CEL, Using more fuel than normal also. Please help he has thrown a lot of money at this recently. I'm thinking it could be the throttle position sensor or EGR valve but would like to be accurate. Oh yeah this vehicle is a 2.3 liter 4 cyl 8 plug engine.

RE: Surging Idle on 93 Ranger
 

Hey Wheelsup, when I got my 4.0L Rangerlast summer, the throttle was erratic at both idle and cruise. It had no CEL. Both KOEO and KOER pointed to the TPS, and replacement seemed to fix it. I'm not saying the TPS is your problem, but I'd run the tests to see what you have. I don't have EGR's on either of my vehicles, so I'm not familiar with those, but that sounds suspect too.

RE: Surging Idle on 93 Ranger
 

You should be able to find vacum specs to test the EGR. I have not dealt with one in a decade or more and it was from a 1972 Cougar. But they are basicly the same there is nothing that should rattle in it unless the diaphram is bad or a loose chunk of carbon deposit. And the EGR can effect MPG.