'99 4.0 OHV throws P0174 cel but never P0171.

[cr_the_machinist]

My truck has been throwing a Bank 2 lean code for about 2~3 months now. It's not sensor related because I've tested everything, nothing came back unusual. I would assume that if there was a vacuum leak introduced into the upper intake area that it would eventually trigger a leak code on bank 1 aswell. The thing is, it has never thrown a leak bank 1 code ever. So, my thoughts are;

- Check upper and lower intake bolt torque
- Check for exhaust leaks
- Check fuel injector ohm readout
- Replace fuel injector manfold o-rings

Am I on the right track?

One other thing that concerns me on my truck it the Cansiter purge valve. I did the old mouth test with the smaller vacuum hose the leads to the valve. It does not hold a vacuum. Is it functioning correctly? I assume it should because it looks like it houses a diaphragm. I just don't fully understand how its supposed to function.

Any input from you fellas would be greatly appreciated!

 

[cr_the_machinist]

Well, no feedback I see.

Just ordered up some refurbished injectors for a very fair price. Probably pop the fuel rail off Friday morning, check everything out, and replace the old injectors. Just going to see what happens. I'll let you know what comes of it.

 

[ragajungle]

I just went through all this with mine. I did some youtube vid searches for the codes and yielded some pretty cool testing methods. I would say do a quick search on youtube and watch rthe vids for Real Fixes Real Fast.


In my case it was a combination of a leaking upper intake plenum (seam leak) and a upper intake gasket leak.