There appears to be some cracks in my air intake manifold plenum. I am getting lean codes -0171 & 0174. Any recommendations to test whether this is the source of my trouble codes?⁷. Also, what causes these cracks for Future ref? Thx!

 

I have never seen that before, if it is cracked through you could clear it up with a grinder and fill with JB weld pretty easily. That is a pretty thick casting, i cant imagine how that happened with out an accident or obvious force. You could try to fill it with flex seal tape or similar as a test to see if that is your leak. It would definitely cause codes if the crack goes all the way through.

 

Personally I might try JB weld for troubleshooting but I would replace that plenum. For sure any leaks there would cause it to run lean.

 

Can you feel the cracks? I had some weird fluid residue/stains that looked similar.

 

Yeah, spray some wd40 on those cracks with it running and see if it sucks it in. I have never seen those crack. I have several extra if it really is cracked you can have one if you want to pay the shipping.

 

Wonder if the motor was from an accident damaged car. There’s really no reason that this could possibly crack. Have never seen that in all my years on a P38 or a D2, which echoes what others say here.
Wow.

 

Looks like something someone loosing their temper would do lol