'94 Ranger EEC-IV codes 157, 158, 181, 186, 189, 543, 556

[WhyteWolf]

This is my first time posting, so bear with me...
I have a '94 Ranger 4.0, and have been having some strange issues. At random times, often when accelerating heavily such as when getting on the highway, the check engine light comes on briefly, then turns off a minute or so later. I drive roughly an hour to work each day, and it usually occurs between 1 and 5 times per trip. I also have noticed a ticking when accelerating under load (i.e. going up hill). I have been putting in 93 octane gas to reduce the ticking, but it isn't going away. I also had problems where it wouldn't always start, which I traced back to the EEC relay which I replaced about a week ago. I had been hoping that replacing that relay would have fixed the other issues as well, but I guess that was just wishful thinking.
So I hooked up my code reader today, and got a bunch of codes off of the continuous memory check, and no cods off of KOEO or KOER. The codes I got were:

157
158
181
186
189
543
556

I have found the definitions for all of these codes, but most of them don't really mean much to me, so I was hoping someone may have some knowledge of problems that could cause one or more of these codes, so I have somewhere to start. Any help would be greatly appreciated!
Thanks.

 

[MrShorty]

That is an interesting set of codes. Where you got pass (111) codes from KOEO and KOER, that indicates that whatever the fault is, it is intermittent (or at least not present when you did the tests).

Maybe it's because I see the fuel pump circuit as easiest to test, or because I just had to replace the fuel pump in my Suburban (and got similar lean codes as it went out), but I might start with the CM 556. If the fuel pump circuit has an loose connection in it, then the pump will be cutting out, causing low fuel pressure to the injectors, causing a lean condition and the stumbling you describe. Whatever test you devise, recognize that your code list indicates that the fault is at least somewhat intermittent, so you have to devise the test to account for that. I might start with a "wiggle test" to see if I could find a loose connection in the fuel pump circuit. I might put an ammeter in line with the fuel pump (Opera House used to advocate this kind of test when he used to frequent the board) to see if I could see any indication of the pump circuit going open. A fuel pressure gauge on the fuel rail, especially if you rig it up so you can monitor fuel pressure while driving might also help see what's going on.

The 1st gen 4.0 is known for "pinging" like you are describing (if you are indeed describing spark knock). The usual culprits are either a dirty MAF or a vacuum leak or a leaky intake manifold. The MAF is easy to clean, the lower intake manifold leak can usually be fixed by simply tightening the bolts down to spec, and any other vacuum leak just needs to be found and fixed. Vacuum leaks can easily cause lean codes like you're seeing (though they wouldn't effect the fuel pump circuit). Spark knock gets discussed a lot around here, so a run through the site's search engine would be in order.

Try those two areas to see if those are your problems. If so, great. If not, then report back and we'll see what we can come up with.

 

[WhyteWolf]

Thanks for the advice,
I cleaned the MAF today (had to go to the parts store to get a bit to remove it, or else i would have done it days ago...). I have only taken it for a quick spin so far, but i think it may have done the trick. One of the probes on the MAF was pretty nasty.
I should know for sure if it's fixed after i drive to work tomorrow, I'll keep you posted.
Thanks again!

 

[Tbars4]

...Welcome to the forum...

 

[MrShorty]

If you haven't already, I would suggest you clear the CM codes so that if this problem resurfaces (or another one), you'll know that any codes you pull are new and not left over from before cleaning the MAF.

 

[WhyteWolf]

Thank for all of the advice (and the welcome), it looks like cleaning the MAF did indeed fix all of my problems...amazing!
I had forgotten to clear the codes, I had cleared them after replacing my EEC relay, but since the CEL came on after that, It needed to be done again. I cleared them out tonight, thanks for the reminder!

 

[Tbars4]

...you are very welcome and thank you for updating us on your sucessful progress..