system too lean fault...

[import.only]

I just dropped a new engine in my 96 3500. It was a remanufactured 350 vortec. I got a check engine light right off the bat due to incorrect timing. Fixed that, but now I get a check engine light that is on some times and off at others. The fault code is "System too lean (bank 2)". Can some one point me in the right direction with this problem. Thanks.

[taillight]

Look for an air leak. Vacuum hose, Intake manifold gasket EGR or anything on that side.

[import.only]

ok I decided to change the o2 sensor on the right side because it called out bank 2, but I had no luck. I also looked for an intake leak. The light comes and goes. I want to check for a vacuum leak next. What would be the best way to do that? I heard you could let out some propane or butane around the intake to see if it starts idling rough. Is that right? Any other ideas?

[777stickman]

Propane I haven't tried. I use carb or brake cleaner. Need to just spray around intake, TBI, hoses, etc. If there's a leak you'll hear the RPM's change.

Just thought of something else. Do you have any kind of exhaust leak. An exhaust leak can actually suck air into the the exhaust system causing a lean O2 sensor reading.

[import.only]

I don't think I have an exhaust leak but then again haven't really checked. Just pulled the spark plugs and the ones on right seem to have more carbon build up then the ones on the left. I'm thinking that it it might be the injectors. When the engine was out I started clean the intake and when I went to pull the injectors out, two of them had pieces of the plastic clip fell off. I re-used them thinking they would be ok . I'm thinking that one or both of them is sitting loose in there and not spraying right. I'm going to take the intake apart today.