I have the same issues as many other 2.9 owners. Erradic idle. I pulled the codes and got 53,63, and one for the voltage regulator. Now lately the problem seems to be more prevalent during deceleration. C/E light comes on and the Idle bounces. This sometimes ends up with a stalled motor. The other issue occurs when shifting between gears (5spd.) The Idle will climb to 3k for a few seconds and then drop to about 1,100. That seems to be where the truck likes the baseline idle. Obviously not right. I have replaced the TPS, swapped IAC's and checked for vacuum leaks. The tricky part is when I disconnect the TPS the truck seems to run fine, other than the fact that the C/E light is on. I'm stumped. Any help would be appreciated.

 

Were those KOEO, continuous memory (CM) or KOER codes? What was the voltage regulator code? I can't find any voltage regulator codes for a 2.9L. Was the 63 left over from unplugging the TPS?

 

Sorry about the confusion they were KOEO codes pulled by my local AutoZone. I believe that the 63 was a history code. I want say that the voltage regulator code was a 13 or 15 I dont have the info on hand at the moment. I have a new alt/VR from a donor truck that I am going to put on this evening.

 

13 would refer to the IAC valve (aka ISC motor), so that wouldn't be it. 15 refers to keep alive memory power (pin 1 at the EEC 60 pin connector), so that doesn't seem directly connected to the voltage regulator. Did you also get the code definitions from the autozoner?

My first piece of advice would be to learn to pull codes yourself. You only need a paper clip and a cheap testlight. Ken00 has posted instruction (pulling EEC-IV codes) in his tech info post at the top of the Ranger or BroncoII forums. If you don't like his instructions, put "For EEC-IV self test" into your favorite search engine and you'll find several sets of instructions.

SOP when diagnosing codes is to start with KOEO codes (both KOEO and CM codes are output during the KOEO test, you need to be able to distinguish between them). Assuming we understand what the autozoner did, that leaves us starting with a KOEO 53 and either a KOEO 13 or 15.

KOEO 53 - TPS high. As a KOEO code (hard fault, here and now fault) this shouldn't be too hard to diagnose. Do you have a wiring diagram? TPS is a basic potentiometer. Basically need to go over the circuit and look for a short to power, a short between Vref and TPS signal, or other reason TPS signal is higher than expected.

If the 63 was only a CM code and not a KOEO code, then I would assume this is from unplugging the TPS and not worry about it until you get pass codes from the KOEO test and from the KOER test.

KOEO 13/15: depends on which code it really was. Repeat test and get the code number.

 

Well I finally figured it out. It ended up being the Voltage Regulator. Thanks for the help.

 

i got the same problem with my 1990 ranger, where is MY voltage regulator located? i got this info from autozone.com:

Under hood, passenger side, front engine area, mounted in alternator housing
With internal regulator

Under hood, passenger side, front side of shock tower, mounted on fenderwell
With external regulator

what does it look like?

 

its most likely an internaly regulated alternator, so you would have to replace the alternator.

on the off chance its external its a small black box with 3 or 5 wires connecting to it.

Diesel Rod

 

Seems like it is the spark plug wires or plugs themselves. Possibly the distributor cap. While inspecting the truck, with it running, I jiggled the passenger side plug wires and the truck died. I started it back up and it ran fine, til I jiggled the wires again, it died.