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KOEO/CM - KOER codes - what to do next?

BusterXLT

New Member
Joined
February 14, 2008
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City, State
Bellingham, Washington
Year, Model & Trim Level
'93 XLT
So I was driving home from work a few days ago in my '93 4WD Explorer XLT and halfway home it just started running really rough, whether it was at idle or at 50 mph. Smoothed out some when accelerating to 50, but once there... rough.

I am somewhat mechanically inclined, but no expert. (I appologize for the length of this post.)

Got home, raised the hood, checked for vacuum leaks, even while running. Couldn't see or hear anything obvious. Then I started looking at the posts on this site for a course of action, deciding to focus on the posts about getting the KOEO/CM and KOER codes because the CEL had come on, on the way home.

Yesterday I purchased a fuel pressure gauge, CRC MAF cleaner, and some CRC carb cleaner.

I cleaned off the MAF (didn't look especially dirty), cleaned out the IAC, I think, (that thing at the top of the engine to the right as you face the vehicle from the front... held on by two bolts and has an electrical connection). Let dry, re-assembled, started the vehicle and it seemed to
cure the problem... for a while. A bit later it started running rough again. So, learned how, and played with, getting the codes, checking fuel pressure.

I decided that today I would start cold so that I could post a clear (as possible) picture of what the symptoms are.

I attached the fuel pressure gauge and cleared the codes. At this point the fuel pressure was reading 39-40 psi and holding (I could hear the pump run whenever I turned the key on).

Took readings of KOEO: 111 111 *pause* 1 *pause* 111 111.

Removed the jumper wire, started the engine to warm it up (KOER needs a warmed up engine, right?). Let it run, which the idle needle settles below the 1 on RPM gauge with black between the white '1' and the white needle. Warming up shows no signs of problems until about 8 minutes into the warm up, and the roughness starts. Revved up the engine to try and keep it from running rough and tried to hold it at about 2K rpms with a little success (I didn't know how long it needed to warm up, so my goal was about 10 minutes). During this time the fuel gauge showed about 31 psi, and during the rough idling it would jump around inbetween 30 & 40 (so I think pump and regulator are ok).

Shut off the engine, plugged in the jumper wire and took the KOEO readings:

159 159 *pause* 1 *pause* 157 158 157 158

Started the engine for the KOER codes, CEL flashed 3 times, I pressed and held the brake pedal. I waited for the single CEL flash while the engine ran roughly. Got the flash and goosed the the gas pedal.

KOER codes: 412 116 159 412 116 159.

Noticed black residue on the ground below the exhaust pipe outlet.

I'm thinking the MAF needs replacement, but is there more I could test?

Should I be getting the 116 even after a 10 minute warm up?

The temp gauge on the dash does always seem to read low, never in the normal range. I probably should have replaced this long ago since I am now
understanding how these sensors all rely on each other.
 




MrShorty

Explorer Addict
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December 27, 2001
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City, State
Spanish Fork, UT
Year, Model & Trim Level
92 XLT and '87 Bronco II
KOEO 159 seems to often end up being a bad MAF. I expect there are ways to test the MAF, but I'm not familiar with the specifics.
 




Harpua216

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June 10, 2011
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City, State
PA
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1999 Mercury Mountaineer
just went through this and can point you in the right direction though i dont have the exact specifics. but mrshorty is correct, you can check it two ways, one would be to check the connection to the computer and the other is by back-probing the MAF sensor wires with a voltmeter.. with KOEO the volt meter should read about 10V or whatever the battery voltage is. when you turn it over at an idle it should be between .5-.7 and running if i remember correctly 1.5 to 3.0 while at high idle.
 




BusterXLT

New Member
Joined
February 14, 2008
Messages
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City, State
Bellingham, Washington
Year, Model & Trim Level
'93 XLT
The MAF was the problem. I ordered the part from a local Ford dealer ($169.16, not including the $75 core charge), and when I went to pick it up discovered that the gasket doesn't come with it. That would be another $29. (really? for a piece of cardboard?). So I made my own out of a roll of Fel-Pro gasket sheet. ($6 with plenty to make other gaskets). After putting it all together, started it up and back to normal! All CEL codes were 111's.
Just want to thank MrShorty & Harpua216 for confirming my CEL results. Wanted to make sure to post success results so others can see what happened.
 




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