My dad's 99 ranger 4.0L OHV had the check engine light come on. It threw a code "system lean (bank 1)" My dad also said it was running really rough. I checked it out and tried to see if any of the cylinders on the passenger side were not firing. I was thinking that maybe one of the injectors was not working so I cleared the code and drove it for awhile and it drove perfect, no missing, no more light. Has anybody had this problem. Only thing i can think is that the O2 sensor on is started to go bad. Any insight???
Thanks

 

yeah oxygen sensor could be the culprit, my roomate's GT has a couple of CEL codes with "bank blah blah running too rich" or something and the rear oxygen sensors are shot.

 

After a couple weeks, the check engine light came back on. Could the O2 sensor be bad or maybe an injector is partially clogged? Can't hear any vacuum leaks.

 

ha weird.
i ran a test on a windstar yesterday with the check engine light on.
it said cyclinder 1 misfire, bank 1 lean. so i cleared the code, drove it around hard and it ran fine after. not rough, and no light came back on.

 

My 95 explorer(ohv) idles like crap until l i cleaned the maf. Idled better but it has come back so a new maf is needed for that.

 

I cleaned the mass air meter, didn't even look dirty before hand and it didn't change the driveability at all.

 

yeah i had a cel after i made the MAF mod but then i jsut reset the systen again by unhooking the bat for 30 minutes (only needs to be 5 but ehh) and then reconnecting it and idleing itfor liek 15 minutes

and the CEL was off afterwards

 

It leep throwing the 171 and 174 lean code for both banks. I have swapped mass air meters with my truck, changed out the fuel filter, new pvc valve, and ran injector cleaner thru it. Nothing seems to help. Any more ideas?

 

Possible vacuum leak. A couple of common leakers are the rubber elbow on the PCV system or the intake manifold gaskets.

 

Clean MAF, make sure PCV hose is not colaposed in on itself, did you do any exhaust work lately? Listen for any vaccum leaks by ear.... Disconnect battery for 15 mins and reconnect and retest. I'd almost bet money is the PCV hose and that it has oil covering it and it has colapsed.

 

I noticed that when I put the new pvc valve in that hose did have a crack in it where it attaches to the intake manifold. Ill get another one for it and see if that helps. Thanks guys

 

I have had a very similar problem with my truck. It turned out that it was a vacum leak. I replaced the intake gaskets and it took care of it. Here is a link to a how to https://www.ranger-forums.com/forum2...ad.php?t=27084