OK I've got my smoke machine ready to test for a lean condition (P0171, P0174). So now what do I do? Where should I introduce the smoke into the air intake system? Do I need to vent the smoke downstream? I was thinking I would disconnect the air intake just downstream of the MAF, seal the plastic hose up with duct tape, punch a small hole to stick the smoke hose in. (I'm THINKING" my air leak is likely upstream from the throttle, but I definitely could be way wrong here! I sure would appreciate a little advice!! Thanks in advance!

 

I normally remove the top of the filter box. Plug up the tube with a plumbers inflatable ball used for testing water pipes, remove the MAF sensor and introduce smoke there using putty to seal up the round tube in the square hole. You do not need to "vent" the smoke. The leak will vent it for you.

Hope this helps

Jeff

 

I'm with Jeff, I use the MAF sensor hole to introduce the smoke. If you don't have a plumbers ball to plug the intake, I've had success with a sheet of saran wrap laid over the air filter, just close the air box to get a seal with the saran wrap.

On the LR3, I've found the resonator air box in between the MAF and the throttle body can develop hairline cracks that while they look small can easily throw lean codes.

 

Thanks you two! I'm just getting started in my Land Rover Repair, Masters Degree!!! This is Lesson 3 of 8,996!!!!

 

I did take this advice and used the MAF hole for my test (Sealed with modeling clay). I found two cracks on the air intake plastic housing between the air filter box, and the throttle. No other air leaks showed up. I sealed these up with epoxy and I was feeling really good. Unfortunately, the LR3 must not have been feeling so good because the check engine light returned on and the same lean codes (P0171, P0174)

I think I'm going to do the smoke test over again and see what I can uncover. So far I've:

• Replaced the fuel pump. No codes prior to this . . . (which may be a hint that I've missed until writing this!!)
• Replace the PCV valve.
• Cleaned the throttle,
• Ran injector cleaner through the fuel
• Cleaned the MAF.
• Replaced the MAF
• Sealed 2 air cracks in the plastic air intake

I'm not sure how to check fuel pressure coming into the injectors, but I'll have to figure that out I think.

 

4:30… bladder is a must have, right under the MAF hole - getting the smoke in the system at the earliest part of failure.