Hello all. I have a 2000 suburban. Every so often (a couple of times a week), the check engine light will come on. The code being thrown is Lean condition bank1 and bank 2.
Yesterday, I was about to pull out of the driveway and it started idling very low (300 rpm). After a little revving, it seemed to recover. I don't know if the two things are related.
Up to this point I have changed the air filter, mass air flow sensor and does a test for vacuum leaks in the manifold (could not find any leaks).

So any ideas what else it could be? I'm leaing towards O2 sensors and also plan to replace the fuel filter today.

Any input greatly appreciated.

Thanks

 

Could be a fuel pump. Check your fuel pressure.

 

Ok. Will do.

 

I went and picked up a filter and a pressure tester. I checked the pressure before changing the filter and was getting like 30psi. After changing the filter, the pressure appears to actually have gone down to like 20 - 25psi.
So now i suppose it could be the regulator or the pump correct? Any know way to rule out the regulator?

 

The fuel pump on my '02 Tahoe crapped out about two months ago; my fuel pressure was down to 15 psi--after fuel pump replacement, it shot up to 60 to 65 psi. I can't say for sure that the pump is the problem, since it sounds like your engine is running....in my case, my Tahoe died on the road, and when I got it towed home, it started, sputtered, then died...I couldn't keep it running. To validate the fuel pump, I pulled the air intake hose off the air box and sprayed a couple of squirts into the intake hose...started right up.....if I continued to squirt carburetor cleaner (one spray at time when the engine began to die out) it came right back up to running smooth. Fuel pressure regulator would be a cheap trouble shooting step. If you checked for intake leaks, that would take care of the issue of intake gaskets; I went through that several years ago; rough idle in the morning at cold start, then it smooth out as it warmed and from time to time lean codes. I never tried it, but if you suspect your fuel pump is going bad, I was told that you can try smacking (maybe slightly harder than a tap) the center of your fuel tank with a rubber mallet, your hand, or shoe, just enough to give the fuel pump a small shock--this sometimes gets it to fully operational to get you a little further down the road....I mention this because your fuel pressure seems to be low....if your fuel pressure jumps to where it's supposed to be, and I believe it should up near 60 psi, after trying this trick, then it may confirm a problem with your fuel pump.

 

Thanks. I went ahead and purchased the fuel pump. I'm at 170K so I'm pretty sure that is the problem. I did not expect the job to be this hard but working underneath a car is not the easiest thing to do. The biggest problem is all the hose clips and trying to get them off. What a pain.

 

Hopefully you went with the OEM fuel pump, often times the cheaper store brands are just that, cheaper and won't last you the 10+ years you got from the original... Also its speculated that keeping the tank at least 1/4 full and re-filling at that point also helps keep the fuel pump cooler in hot climates... The thinking is that that fuel helps cool the fuel pump motor... (read don't run the tank near empty too often... )

 

Sage advice. You beat me to it.

 

Thanks Sensei 73shark

 

+1 from me on going OEM dealer on the fuel pump, or at minimum go AC/Delco. We buy plenty of GM parts at work for our fleet, and there seems to be a difference between buying the GM OEM packaged dealer item and AC/Delco branded item--if I'm not mistaken, Delco is not as closely affiliated with GM as they once were. My original pump went out at 65k miles and replaced with a Delco--the replacement Delco lasted about 130k miles. From all my research, it appears that these GM fuel pumps go out often because they are considered a maintenance item--there's definitely nothing routine maintenance about dropping your tank to replace the pump. I'm sure there's some benefit to keeping the pump cool by keeping enough fuel in your tank to keep the pump mostly submerged, but I'd bet money that keeping up with fuel filter replacements probably counts more to reduce overworking the pump from a restricted filter.