I have a 2001 4.0 SOHC Ranger. I am getting 175( Too rich on bank 2) and 171 (too Lean on bank 1)error codes at the same time. The engine has low power and uses lots of gas. Would this be a bad O2 sensor? If so which one.

I did a vacuum leak check, I could find no vacuum leak. I am pulling about 17 in/Hg vacuum at idle. I did a leak check around the intake manifold using the carb cleaner method, no leak detected. Tried a new PCV valve. Pulled the wires off the coil pack one by one while engine was idling, I saw good spark on all coils.

I also get missfire errors 304,305,and 306 which are missfires on cylinders 4,5,and 6. I assume because the computer is setting the fuel to that side too lean to compensate for the too rich error it is recieving on the 02 sensor. Does this mean that the 02 sensor on that side may be bad. Or would the too lean from the other bank cause the misfires on 4,5,and 6

Plug wires are the next thing, they should be replaced anyway.

Any ideas?

That's a weird one. My first inclination would be to make sure the MAF sensor is up to par. Cleaning it couldn't hurt.

Sorry, I should have said the MAF is new.

Lean bank one, rich bank two.
Bank 1 is getting the same exact enrichment commands as bank 2.
Yet, one side is lean and the other is rich.

So:
Bank 1 has one or more fuel injectors that have their flow obstructed or are not functioning. The PCM reads bank one lean and tries to compensate by increasing the enrichment, now the entire engine is rich (except the one cylinder the is not getting fuel) and here we are.

It MAY be one injector on bank two (driver side 4,5,6) is leaking, but this would show more serious signs like sputtering/rough idle.

Test: Use a long screwdriver/rod as a "stethescope" and make sure the injectors are "clicking", if not, you found your bad one. If it is bank one (pass. 1,2,3) then it is stuck closed or the coil is burned or the connector is unplugged. If it is two, it is stuck open.

Check my site, I have 97-01 injectors...

http://rogueperformance.com/BlueprintedFuel.html

There are other possibilities, but this is the most likely...

I took the Intake Manifold to see if I had a Vacuum Leak.

First thing I noticed Is Bank one Intakes were real clean, Bank two was quite Brown, so it looks like the error codes were right bank one is too lean and bank two is too rich.

My question, It can't be just one injector that is causing this problem, It would have to be all the injectors on bank 1 are bad, or the whole fuelrail on bank 1 is bad somehow. Any advice before I button the intake back on?

By the way, I noticed a very slight leak on the intake manifold gasket on cylinder 1. It was a very small leak, but could this be the cause of my problems?

Before you buttoned it up, you changed out the intake gaskets with new ones from Ford, right? If you can see a problem with one, then they are all suspect.

RockLedge

I went to Ford to get new Intake Manifold Gaskets. AlL I can say is Holy Crap. The difference between the FelPro that were in the manifold and Ford ones I bought is night and day. The FelPro were loose in the groves and difficult to keep in place while installing the manifold. The Ford ones are twice as thick, fit snugly in the manifold. After putting everything back together. The engine works great, more power, no error codes.

This the second time I have been plaged by FelPro Gaskets. From now on it is OEM Only.

Thanks

RockLedge

I went to Ford to get new Intake Manifold Gaskets. AlL I can say is Holy Crap. The difference between the FelPro that were in the manifold and Ford ones I bought is night and day. The FelPro were loose in the groves and difficult to keep in place while installing the manifold. The Ford ones are twice as thick, fit snugly in the manifold. After putting everything back together. The engine works great, more power, no error codes.

This the second time I have been plaged by FelPro Gaskets. From now on it is OEM Only.

ThanksFrom what I've read, Ford re-designed their SOHC intake gaskets a few years ago, made them thicker. I think Ford was actually proactive in that regard.

Now let's hope we don't see any more codes for while. ;)

Sweet, good info. I'll be getting the OEM parts when I do the wife's injectors ('98 SOHC Explorer).