I went to get plates on my new 98 ranger 4.0/MT 4x4 and failed cause the CEL was on. I figured that would happen.
So I went home and pulled the codes and got
P0171 Lean bank 1
P0174 Lean bank 2

I figured with these codes and the high/floating idle I might have a vacuum leak but when I sprayed down the engine compartment I found nothing. I have a snap on scanner to work with, any suggestions on what to check next?

Thanks

 

pcv valve working?

 

Where is the pcv valve on this thing?

 

PCV valve change - YouTube

 

If the PCV system checks out, even though you've sprayed the engine down, these 4.0L engines are known for intake manafold leaks, so you might try re-torquing the upper & lower manafold fastners, in the specified sequence, to the spec value & see how it goes. If its leaking there & your lucky, maybe the gasket hasn't sucked in & deformed such that it'll need replacement.

Of course, All vacuum lines & their fittings belong on your suspect list & this includes the suggested PCV valve, its hoses & fittings, along with the in cabin heater/ac vacuum lines, controls & actuator motors & the brake booster & its vacuum line & fittings..

Be sure to post All trouble code Numbers, as they can offer up good clues that can help narrow down your trouble shoot.

Let us know what you find.

 

The spray check rarely detects vacuum leaks. A better approach is to do a smoke test, which does require a smoke machine. Many good shops have one. That will find any and all vacuum leaks in a hurry. I think you still have a vacuum leak, but it wouldn't hurt to replace the PCV valve and check the condition of its hose. Use a genuine Motorcraft PCV valve. I have found many aftermarket ones that either do not seal, or do not seal when exposed to the heat and vibration of an engine. The Motorcraft one is not expensive or hard to get, so I thinks its worth it.

The 4.0L is often known for the intake manifold gaskets going bad, especially as the engine gets older. If you have the SOHC, you can use whatever brand gaskets you prefer. If you have the OHV engine, get the Motorcraft ones, only the Motorcraft is designed to correct a factory defect by using a thicker more durable material, the other brands are based on the original faulty design and are too thin to seal on a vehicle that has higher mileage. It is also possible that you could have a leak at any one of the injector seals, so make sure you replace all of those too if they don't come in your gasket set, make sure you pick them up. Just check what comes in the kit, and if injectors O-rings are not part of the package, ask your parts supplier for those too.

 

a dirty/bad MAF can cause those codes too.......clean the MAF......do you have an "oiled" air filter?

 

I couldnt find any external leaks, and I figured it had to be a vacuum leak due to high idle, pegged fuel trims, lean bank 1&2 codes, and 1-2% IAC duty cycle. So I ended up tearing into it expecting to replace lower intake gaskets. What I found was a cracked and epoxied fuel rail and the rubber gaskets looked sucked in. I replaced all the gaskets and that epoxied piece (i'm pretty sure this was my biggest leak), and the fuel injector O rings since I was in there.

It runs great now, perfect idle, and way more power. Thanks for your help guys.

 

Good trouble shooting find, fix, feedback & to hear all seems well & your "on the road again"!!!!

 

just my .02 the smoke test is a great way to find vac leaks but my grandpa used a cigar, popped the booster hose and just started sending mouthfulls of smoke through it.