I've got a 94 with the 2.3l. For the past year or so sometimes when I start the engine and begin backing out I'll notice the idle drop. It also shows up as the voltage gage drops down for a few seconds, then the engine idles back up to normal and runs fine. Never happens while driving. New fuel pump and filter, new IAC, cleaned out the EGR valve about a year ago. Guessing it's a bad TPS or perhaps an EGR problem.

 

PCV replaced? Bad temp sensors? Dirty injectors? Dirty electrical connection?

It is just a process of clean and check unless it is showing a code.

Do you have a good OEM manual with diagnostic routines?

 

Does your 94 have a throttle position sensor?? My 85 does, as did an old Escort 1.9 FI that I used to own. The idle speed controller started acting wacko on both vehicles. The "book" says that the idle speed is factory set, and not adjustable. Well, the one on my Ranger is fully adjustable technically, maybe not legally (emissions). I adjusted my controller BACK some (so it wouldn't put the idle up too high on its own), then used the idle set screws to do more of the idle speed controlling than they did before (carb had 2 screws, 1 hot curb idle, 1 choke fast idle). But I would take the advice of the previous post FIRST, before adjusting anything, and CLEAN EVERYTHING! Especially electrical connections (lube too).

 

OOPS! Just realized I asked a stupid question. You suspect a bad TPS, which is Throttle Position Sensor. Never mind.

 

 

Always keep a fresh PCV in this motor. Injectors were professionaly cleaned about a year ago and I always put a bottle of injector cleaner in the motor at an oil change. The temp sensor is original but never heard of this being a possibility? I'm guessing it's dead spot in the TPS. No engine codes. I've read that the MAF can cause this and I cleaned it per the instructions found on the tech pages.

 

A dead spot in the TPS would show up all the time, since it only shows up when the engine is cold look there first:-)








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