Trouble Code Repair

[Joes4x4Ranger]

My 91 Splorer has a (Code 013- RPM not within Self-Test Lower limit) in the KOER Self test. What is the most likely cause and how do I check it.

What manual do I need to help decipher these codes? Hynes and Chilton both give great info about OBTAINING the codes but JACKS%*T about what to test for each code.

 

[MrShorty]

From what I've seen, KOER 12 or 13 are usually not very helpful. Basically all it means is that the computer didn't like the idle speed during the KOER test. Once when I was running the KOER test, my 2 year old "assistant" was turning the steering wheel during the test. The variation in idle caused by the changing load of the steering pump triggered the KOER 12/13. Were there other codes? What symptom are you diagnosing? If that was the only code, you'll do better diagnosing by symptom.

A couple of things you might check: vacuum leak and see if the IAC valve is clean.

As for a manual: The best resources I've found for deciphering codes is a "professional" repair manual. Libraries around here carry Motor or Mitchell -- look for the "engine performance" volume for your year. I seem to recall that some have found factory repair CD's on ebay for a reasonably price, that may have the same information. Note that a typical EEC-IV diagnostic section is ~200 pages. Look for something that has a good description of the test procedures, breaks down the codes by engine and year, and has circuit "pinpoint" tests for each code.

 

[Joes4x4Ranger]

Thanks. The 13 was the only code. I'm having problems with my rig at low RPM, like idling slowly in gear. It surges and sometimes bucks like you stabbed the throttle. This is very irritating when slowly crusing off-road or creaping up to a stop light. I put a new IAC on the rig a couple months ago along with a MAF cleaning.

I have not been able to find I vacuum leak around the manifold with ether or carb cleaner. All lines are connected and feel OK, not hard and brittle. My rig is non EGR so that eliminates that set of problems. Could it be a defective Autozone IAC?

 

[MrShorty]

Could it be a defective Autozone IAC?

There are very few guarantees in life. Yes, it is possible that you've purchased an IAC that is defective out of the box. Does the valve look clean? Have you checked for electrical continuity through the motor? If it checks out in those respects, I would be inclined to believe it's ok.

Have you checked fuel pressure? Fuel filter due replacement? Any sign of spark leak or other "tune-up" type problems?

 

[bluesman2333]

Having just had a bad MAF from AZ, I wouldn't rule out a bad part yet. One thing you do need to do is unplug the IAC and start the engine. If it won't idle, turn the idle stop screw up a little then adjust the idle stop until you get the correct idle speed. Plug the IAC back in and see if it's better. Doing the .96 volt TPS adjustment seems to help too.

 

[Joes4x4Ranger]

Having just had a bad MAF from AZ, I wouldn't rule out a bad part yet. One thing you do need to do is unplug the IAC and start the engine. If it won't idle, turn the idle stop screw up a little then adjust the idle stop until you get the correct idle speed. Plug the IAC back in and see if it's better. Doing the .96 volt TPS adjustment seems to help too.

How do I do .96 TPS adjustment? Send me a link to that thread. I checked out the IAC as suggested and it's OK. I'll try the idle stop thing this afternoon.

 

[bluesman2333]

Try this: http://www.explorerforum.com/forums/showthread.php?s=&threadid=79362