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Help with codes

andy21918

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1993 XLT
I have a 1993 Explorer XLT. Did the self test with a paper clip and this is what I got.


KOEO 111,157,177
KOER 116,137,538

Code 157 says MAF Sensor circuit open. I got a sensor from junk yard and still did the same thing. Would a bad sensor throw all these other codes? Thanks in advance
 
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doonze

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I have a 1993 Explorer XLT. Did the self test with a paper clip and this is what I got.


KOEO 111,157,177
KOER 116,137,538

Code 157 says MAF Sensor circuit open. I got a sensor from junk yard and still did the same thing. Would a bad sensor throw all these other codes? Thanks in advance

Possible, a bad MAF can throw everything out of whack. But if you tried a different MAF and got the same result, I'd think it was something else.
 
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andy21918

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Yeah thats what I would think. But maybe the sensor at the junkyard was bad too.
 
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RaiderKC

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Its possible that both were bad, i have heard a few stories bout the MAF sensors causing a few problems like that.
 
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MrShorty

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SOP when resolving codes is to start with KOEO codes (you report a 111 pass), then move on to KOER codes.

KOER 116 could be operator error. Make sure the engine is all the way warmed up before the KOER test. If the engine is having trouble coming up to temperature, then look into cooling system issues (like a stuck open thermostat).

KOER 538 is almost always operator error. Check through your instructions and make sure you are performing the "goose" test at the right time.

KOER 137: Left/Front O2 sensor indicates rich. (Coincides with the CM 177). We'll never assume the computer is infallible, but I would expect an MAF problem to affect both banks rather than just one. Where the problem seems to be isolated to the driver's side, I'd start there. From spark plug condition or exhaust condition, does that side seem to be running rich as the O2 sensor indicates or does that side seem to actually be running lean? If you swap the right and left O2 sensors, and clear the codes, does the trouble code switch sides or does it stay on the driver's side? Any sign of fuel delivery problems (in other words, fuel pressure within specs)?
 
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andy21918

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1993 XLT
SOP when resolving codes is to start with KOEO codes (you report a 111 pass), then move on to KOER codes.

KOER 116 could be operator error. Make sure the engine is all the way warmed up before the KOER test. If the engine is having trouble coming up to temperature, then look into cooling system issues (like a stuck open thermostat).

KOER 538 is almost always operator error. Check through your instructions and make sure you are performing the "goose" test at the right time.

KOER 137: Left/Front O2 sensor indicates rich. (Coincides with the CM 177). We'll never assume the computer is infallible, but I would expect an MAF problem to affect both banks rather than just one. Where the problem seems to be isolated to the driver's side, I'd start there. From spark plug condition or exhaust condition, does that side seem to be running rich as the O2 sensor indicates or does that side seem to actually be running lean? If you swap the right and left O2 sensors, and clear the codes, does the trouble code switch sides or does it stay on the driver's side? Any sign of fuel delivery problems (in other words, fuel pressure within specs)?


I havent tried changing or swapping out the o2 sensors. When the engine is cold it spits and sputters and has loss of power. Once its warm it runs fine but the check engine light comes on. Like I said I have changed the MAF sensor and a new fuel filter. I dont know how to check the fuel pressure. But when the engine is cold the exhaust has a strong smell of gas. So what should be my next step? Swith the left and right sensors before that cats? And see if the codes change? But if it is the o2 sensor why is there a MAF code?
 
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MrShorty

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But if it is the o2 sensor why is there a MAF code?
O2 sensor and MAF are both part of fuel mixture control. EEC-IV computer isn't always very smart (is "smart computer" an oxymoron?), so it can't always tell whether the fault is with the O2 sensor or the MAF or something else. So your computer has decided to report both codes and hope you are smart enough to figure out what's really wrong. I might suggest finding Glacier991's "primer on computerized engine control" (or some such title) where he has a basic description of how your computer is involved in controlling fuel mixture.

I dont know how to check the fuel pressure.
Find Glacier991's checking fuel pressure mini-diary (under the hood forum I believe). IMO learning how to check the fuel pressure is a necessary skill for anyone serious about DIY diagnosing a modern fuel injected engine.

But when the engine is cold the exhaust has a strong smell of gas.
This is consistent with a rich running engine. This suggests that the O2 sensor is reading correctly and that the fault lies elsewhere.

At this point, I would probably first start by checking fuel pressure.
 
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andy21918

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So the codes are indicating oxygen sensor saying system is rich. If I was getting low fuel pressure it would be lean correct? If the MAF sensor is bad and thinking there is more air then there is it would mix more fuel causing the engine to run rich. Right? I have already changed the fuel filter and as you say the smell of gas in the exhaust probably means the o2 sensor is correct. I know you said a bad MAF would cause both o2 sensors to throw codes but do you think I just got a bad one from the junk yard? Thank you Mr Shorty for all your help.
 
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arco777

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Not too long ago I was having problems with mine; it was throwing codes saying O2 sensor problems and after replacing them, no change. First thing I did was swapped the MAF out with a neighbor's that had been "working fine". No effect. Replaced the EGR valve, no effect. Replaced plugs, wires, and more. The engine would barely run.

Finally I disconnected the MAF on my dad's advice and the idle stabilized and the engine ran fine. Try it! A brand new MAF fixed the whole problem, but first I had to run the motor for a while with the MAF disconnected. Something about resetting the barometric map? Whatever the case the new MAF made everything better once I'd let the motor run for a little bit without one.
 
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andy21918

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Well when I unplug it the engine runs horrible. How long did you leave it unplugged?
 
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Currency

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Well when I unplug it the engine runs horrible. How long did you leave it unplugged?

I left mine unplugged for less then five miles. Had to pickup my son or I would have left it off for a bit.
 
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arco777

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I left mine unplugged until I bought a new MAF the next day - I think unplugging it makes the computer substitute a best guess at what the reading would be (or maybe it uses manifold pressure, can't remember). Went from un-driveable to about 80% performance when it was unplugged, back to 100% with the new MAF. Not sure why the motor would be running much worse with it disconnected.
 
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