Trouble codes- 94 Sport

[IslandSport94]

My check engine light came on several times today, so I ran a code scan and came up with codes 157 and 172. As I read the code guide, code 157 deals with the MAF sensor input voltage, and code 172 is Heated Exhaust Gas Oxygen sensor detects lean burn, bank 1.
OK, so that tells me what? Are they related? Or do I have 2 seperate problems? Possible solutions?

Thanks in advance, your help is appreciated.

 

[MrShorty]

there's a good possibility they may be related. According to my code lists,both of those should have been KOER or memory codes, so can I assume it passed the KOEO test? Did you perform the KOER test? It can be easier to diagnose from the KOER test (her and now) rather than from memory (sometime in the past) codes. Be sure to follow the directions (don't want false lean codes due to a cold O2 sensor).

It can also be important to remember that codes don't necessarily mean bad sensors. The computer can't distinguish between a bad sensor or an unplugged sensor. The computer also can't tell when a fault is caused by something it doesn't monitor, like fuel pressure. A complete diagnosis of this is going to involve:
1) the KOER test if you haven't performed it yet.
2) A fuel pressure test.
3) check for vacuum leaks.
4) If the fault is intermittent enough to not show up in the KOER test, then you are going to need to adjust your diagnosis to account for the intermittent nature of the fault.

 

[IslandSport94]

Mr Shorty,
Thanks for the reply. To be more specific, during the course of a 1 hr 20 min 75-80 mph drive, the CE light came on 3 times. The KOEO test was performed immediately on arrival and showed 3 sets of the same 2 codes. Did not run KOER. The Ex has been running a little rough for the past week, kind of a "time for a tune-up" feeling. I haven't changed the fuel filter in the 70k miles that I have owned the Ex. Could it be that simple?

 

[monkeydude3]

It could be. My auto instructor has a 1997 ranger (4.0L OHV) that exibited similar symptoms with similar codes (they were different due to it being newer with OBDII and a different array of sensors) and it ended up being a bad MAF.

What you could do, is as stated before, test the fuel pressure (should be at approx 35psi idling), and then do a full tuneup and inspect all your connections to sensors under the hood you can. For the heck of it, disconnect them and clean them with spray electrical cleaner and re connect. Can't hurt.

A tuneup in my book for your motor would include plugs, wires, fuel filter, air filter, pcv valve and a couple bottles of injector cleaner.

NICE! you have a 5 speed! seems like you have the same setup as me. Except I have four doors and two wheel drive...

Take care!

George

 

[MrShorty]

3 sets of the same 2 codes?? Doesn't seem right. You should get one set of codes at the start of the KOEO test (KOEO codes), the same codes repeated (set 2), a long pause, a "separator" pulse, a long pause, and another set of codes (memory codes. set 3), and, finally, the memory codes repeated (set 4). Also, an O2 sensor code can't be a KOEO code, because O2 sensors are not tested as part of the KOEO test.

From your description, it seems that it may not have passed the KOEO test, though I wouldn't expect either of those codes to be KOEO codes (especially the O2 sensor code, because O2 sensors aren't tested during the KOEO test). If it didn't pass the KOEO test, then we need to figure out what the KOEO codes were.

Have you tried the KOER test yet?

A dirty fuel filter could cause enough restriction in the fuel flow to cause low fuiel pressure, which would cause the engine to run lean, so, yes, a fuel filter could conceivably cause the codes and symptoms you describe. As a maintenance item, it wouldn't hurt to change the filter.

 

[Positive Vibes]

I'd try cleaning the MAF first. Its easy and doesn't take long. As stated before the codes are there to help "guide" you to the problem. Hows the air filter. Also the PCV valve is a cheap check.

 

[IslandSport94]

Here is the sequence of codes during koeo:
111
111
111
157
172
157
172
157
172
Just cleaned the MAF/reset PCM today and the K&N is drying as we speak. Pulled the PCV and it was clean and rattled freely, but will replace anyway. Plugs are relatively fresh,(well, the memory of replacing them is fresh, anyway). Haven't changed the wires, so that is up next. Will replace the fuel filter on Wed, my next day off. Still haven't run the KOER, maybe later today. I use Lucas injector cleaner about every other month. Seafoamed the intake last month. The Ex has 110k miles on it.

Thanks for all the help.

 

[MrShorty]

I guess the newest EEC-IV repeat each set of codes three times instead of twice (which is what I'm used to).
So it did pass the KOEO test, which means the best next step is to run the KOER test. Be sure to follow the instructions, so you can get past the "operator error codes" (ie "no TPS change during goose test" "BOO switch not detected" etc.) It may take a couple of tries.