Lean bank 1&2

[Jsommers]

Ok so I have a 96 ranger with the 4.0 and the 4r55e automatic tranny

so it was running perfectly fine until the other day. I had been driving around with a check engine light because I had checked it and it was some emissions code so I wasn't worried. I took my code reader the other day and looked and it now said that it was lean bank 1&2 but it had been running fine before I checked it. Now the check engine lights on and my truck won't idle very well and pretty much almost stalls at idle. I also get a hissing noise from under the hood. But once you get going it acts fine and has all the power it did. But when you stop at a light the truck wants to jump forward and idles very rough. So I'm thinking a vaccum leak. But any ideas where? Is it the lower intake gasket or something else?

 

[BlackBII]

Hissing noise and running lean is most likely a vacuum leak.

Look for disconnected or broken/cracked vacuum lines going to and from the throttle body and intake manifold.

Intake manifold gaskets can leak, but that isn't all that common.

 

[Jsommers]

I thought the intake gaskets were very common on the ohv 4.0 like mine?

 

[Hahnsb2]

Yes, they are fairly common to leak with the plastic intake manifolds (95+). I believe it's usually the upper that leaks.

 

[Bruce]

I had the same problem on my 2002 ..it turned out to be PCV hose was split....look under the upper radiator where its comes out of thermostat housing and you will see it..i replaced the hose with a by pass hose and problem went away.

 

[97RangerXLT]

x2 on checking the vacuum lines going into the intake and the pcv valve hose (yours is much different than Bruce's, it will be about 4 inches long in an L shape, and toward the back of the engine on the drivers side.)

Also check the grommet that the PCV valve fits in while you are there.. if it is cracked you might want to change it.

you can also spray some carb cleaner around the different hoses and intake areas, if the engine revs up slightly, that's where your leak is.

AJ

 

[BlackBII]

I thought the intake gaskets were very common on the ohv 4.0 like mine?

Its not the gaskets themselves that cause the problem, but rather the torque applied to the bolts by whomever installed the plenum.

You can pull the plenum and see, but doing so will most likely result in torn gaskets, requiring you to replace them anyway. I suggest the starter fluid method or propane torch method to check for plenum gasket leaks.

I'm still betting on a vacuum hose that is disconnected and or cracked. High under hood temps cause the rubber lines to deteriorate.

 

[Bruce]

My bad i didnt pay attention to the year.