1993 Ford Explorer Engine Light

[bfsjr]

I have replaced the fuel pressure regulator, the coolant temperature sending unit, the coolant temperature sensor, fuel pump relay, and the check engine light still comes on and the code is 157 indicating low voltage regarding the mass air flow sensor. I have not yet replaced the mass air flow sensor. My fuel gauge reads empty all the time so I suspect the float in the fuel pump/sender has filled up with gas as these brass floats do over time.

When the check engine light comes on, the vehicle stumbles terribly as though the fuel pump is not delivering fuel to the injectors. I have not replaced the fuel vapor canister yet but I don't think that's what's wrong.

Anyone have any ideas as to what my problem is?

 

[mikeinri]

I'm sure someone with more experience will chime in, but I think it is highly unlikely that you would get a code for the MAF for any reason other than having a bad MAF. The MAF is upstream of everything else. Now, if it was a O2 sensor code, that would be a different story, as those at downstream of everything.

One important thing to know about the code, is it KOEO? If so, it is most likely electrical (wiring problem or bad component). I had a MAF sensor code once, turned out to be a broken clip on the wiring plug. I zip-tied it into submission, has been fine since. You could also have a frayed wire, leading to bad voltage or ground, etc.

There are posts here on how to clean the element within the MAF if your wiring turns out OK.

You definitely want to fix this, because MAF problems can lead to other issues, such as bad O2 sensors (at least, that's what a dealer told me when they replaced a bunch of stuff a few years back, truck was shooting soot because the MAF was confusing the computer into making bad adjustments on how the engine was running).

I've never heard of anyone replacing the canister, but there's a first time for everything.

Gas gauge is a convenience item, lots of us just use the odometer. Seems like way more work than it's worth to drop that tank just for the gauge.

Hope this helps, keep up posted!

Mike

 

[bfsjr]

Thanks a lot Mike for the info. I think I forgot to mention that I don't think the fuel filter has ever been changed in this vehicle. It now has 170K on it so I thinking the filter may be totally clogged thus causing the stumbles which causes to check engine to come and off. It runs okay first thing in the morning but eventually, it starts to stumble and the CEL illuminates. I don't mind dropping the fuel tank since I probably need a new fuel pump and sending unit anyway.

If anyone out there has any more thoughts please share them with me.

 

[mikeinri]

Fuel filter is always a good idea. If you suspect your fuel pump is bad, that's a much better reason to pull the tank, then you can kill two birds with one stone.

But, I can't stress enough that you should NOT expect either of these things to make those MAF codes go away, it is upstream (technically "upwind") of where fuel enters the engine...

Mike

 

[MrShorty]

Can you give us a complete code output? Did it pass the KOEO test? Did you perform the KOER test? Do you get the 157 from both KOER test and as a CM code, or is it just a CM code? If any of that doesn't make sense, review my "notes on pulling EEC-IV codes" in the EEC-IV forum for an explanation of each type of code and when they are output.

 

[greyboxer]

I'm having an almost identical problem with my 93 XLT. In the past 3 weeks or so that annoying light has started coming on. It never stays on and doesn't seem to run any different. Actually I spent an afternoon checking for vacuum leaks, changing plugs etc and when I was done it really ran alot better. Didn't stop that stupid light though and last week I had to fill up after getting 177km (roughly 110 miles)out of a full tank of fuel. It's sucking it back like water but not running rough at all. Good luck, if you chase your check engine light successfully please post and I'll follow in your footsteps.

 

[bfsjr]

Can you give us a complete code output? Did it pass the KOEO test? Did you perform the KOER test? Do you get the 157 from both KOER test and as a CM code, or is it just a CM code? If any of that doesn't make sense, review my "notes on pulling EEC-IV codes" in the EEC-IV forum for an explanation of each type of code and when they are output.

Mr. Shorty,
I have gotten the code 157 every time I have run the vehicle then come back home after the cel illuminated. I extracted the 157 code in the KOEO test but I have not run the KOER tests as yet. Each time I clear the code 157, I take it for a test drive and when the cel comes on I pull the same 157 code.

 

[MrShorty]

Did you get a 111 before the 157? My code list suggests that a 157 can't be a KOEO code, only a KOER or CM code. If you didn't get a 111 for the KOEO codes, what did you get?

I would also perform the KOER test. SOP is to resolve KOEO codes first, then KOER codes, because they represent "hard faults" -- faults that exist at the time of the test. Hard faults can be easier to diagnose because you know the fault exists during the test, so you should be able to find it as you work through all the possible causes.

After you get pass codes (111) from the KOEO test and the KOER test (meaning no hard faults), then go on the CM codes. If you're getting KOEO and KOER pass codes, that will usually mean the CM codes are pointing to intermittent or inconsistent faults, which means you have to adjust your diagnosis to account for the inconsistency.

 

[dyazdani]

I am having a nearly identical problem with mine. In my case, I get a 111 followed by a 157 for BOTH the CM and KOER codes.

I suspect his is doing the same. Sometimes that 111 catches you off-guard, it did me the first time

 

[bfsjr]

Finally I think I have solved the 1993 Explorer CEL problem. After replacing the ECT sensor, the coolant temperature Sending unit, cleaning the Maf Wires, putting in a new radiator cap, a new fuel filter, cleaning the IAC valve and still seeing the CEL come on, I noticed the positive battery cable had formed a lot of white corrosion at the positive battery terminal. I cut back the white corroded part of the positive cable and cleaned about an inch of fresh cable and bolted this into a new battery terminal, cleaned the positive battery post, and bolted the new terminal back on the post. It runs fine now with no CEL and no stumbling when accelerating. I suppose that the positive cable had become so badly corroded that the current from the battery was intermittently being cut off the the computer thus causing a stumble and the CEL to come on. I still have to contend with the fuel pump sender now but my CEL problems are now fixed.

Good luck to anyone else out there with my similar problem

 

[tmosesjr]

I have replaced the MAFS, TPS, fuel pump, cleaned out the tank, fuel filter (twice), and both the fuel pump relay and the EEC relay.

My check engine light comes on only on occasion. Like yesterday, after replacing the TPS and letting the car sit all night, it ran like a bat outta hell all day, the CEL never came on.

Today, however it came on while driving, again. It's weird. When the light is off, the truck runs smooth, quiet, and powerful. But sometimes as it drives, the light comes on and it jolts, and only way to get up speed is to very slowly press the gas pedal. If Im at a stop light or sign, and the light comes on, it almost dies. And it will surge forward, and the light goes out and everything is smooth as heck. But then it goes on and of and on and off. From smooth to rough to smooth.

And just to add, There are no leaks, nor does it burn oil.

Any further suggestions are greatly appreciated.

Its sucks the gas, too when the light is on.

And I got the OBD! code 121, which indicated the MAFS.

 

[MrShorty]

Double check your code, my code list says that 121 is for a TPS fault.

Was it a KOEO or CM code (see my notes on pulling EEC-IV codes thread if you are unsure how to tell the difference)?

 

[tmosesjr]

Most recent codes

After awhile, the engine started running smooth, gas mileage got better (200 miles per tank versus barely 100 per tank before) when I started using a deep clean additive. But the CEL still came on, except it would only come on after three miles of driving. Turn it off and back on, same thing. No light until the 3 mile mark. But it would sit and idle forever and the light would never come on. I put a brand new Fuel Pressure Regulator on it last night. No Change.

Now its back to doing the same thing as my original post. When I did the codes, I got 111, no fault, and 172, rich on the right side. What does that mean and how do I fix this? PLEASE HELP!

Thanks,
Thomas Moses Jr

 

[MrShorty]

Assuming this is from the KOEO test, the first 111 means that it passed the KOEO test. The 172 is a CM code, which means the computer thought that side of the engine was running rich at some time. To be precise, the passenger O2 sensor voltage was constantly higher than the computer thought it should be.

A KOER test might be useful, to see if the 172 is consistent.

If you pull the passenger spark plugs, do they agree with the code, that those cylinders are running rich, or does it look more like they are running lean?

What is the fuel pressure?

 

[tmosesjr]

The plugs look fine. How do you check the pressure?

 

[MrShorty]

http://www.explorerforum.com/forums/showthread.php?t=142801

 

[tmosesjr]

OK. I think I narrowed it down to a vacuum leak at the front of the engine. But cant find it. Is there away of testing the Vacuum Switch? Ford Part # E42F-9C915-AA. As in what are the ohms that should be going to it?

 

[MrShorty]

I'm not sure what you are calling the "vacuum switch." Are you referring to the CANP solenoid (I believe it is on the bottom of the throttle body on '93 and '94 engines)?

I'm not sure what the spec for resistance is through that solenoid. I expect if there is continuity through the solenoid, it is (electrically) ok. The overall operation of the solenoid can be tested using the output state test (see my notes on pulling EEC-IV codes) and a vacuum pump.

 

[tmosesjr]

Forget my previous post.

I did the seafoam test, found no vacuum leaks. It is back to worse than my original post. Please help.

 

[idaho_explorer]

im haveing the same problem with my 92.So i changed the plugs(a much needed as they were at .68 as opposed to ford recommended .54) reset the computer and it appeared to stop but like you said ten miles later theres thats light and the bucking with hard acceleration.im gunna try wires as i think min are still the factory as well as the a few other things .my ecu pulls a 341and a 115 so ill change the coolant temp sender as well this weekend (thank god for vacation time from work except i work on cars for a living) and see if that changes it.If it doesnt im going with the o2 sensors and then ill be stumped if that doesnt fix it.But its ok i suppose wish i didnt love my damn X so much cause its a nickel and dimein pos thats for sure.lol well hope to hear you nail the problem before me and save me the time and money and if i beat you to it ill be sure to let you know by this weekend