96 running lean and runs rough when first giving it gas

[anderson1503]

I have 96 with the 5.7 and it's been running lean for a while bank 1 and 2 and can not figure out what is causing it. I have changed maf sensor tps sensor new spark plugs there was a code for malfunction o2 sensor i replaced that and I also put some injector cleaner in the tank also changed fuel filter. The truk idles fine but when I put it in reverse and drive and im crawling/creeping along like backing out of the drive way its stuttering and running rough like its about to die/shut off and usually ill get on the gas a little and it will start running fine. It runs fine once I get going 10-20mph on up from there its just when I fire it up and get to rolling and foot is barely on the pedal. Also not even a week ago truck gauges would go to 0 and would get stuck in 3rd ended up being a ground on back of the engine. I do hear a small leak under the driver side could be exhaust manifold or where the flange is right under it where the pipe connects but I don't think it would cause it to run lean. Tomorrow i'm going to check fuel pressure, all I can think of is bad fuel pump, regulator, maybe intake manifold gasket even though I don't see any signs or even a bad ecm. Any help would be appreciated.

 

Also should there be a little bit of oil in the air intake tube? its also in that vent that just pops in the side that comes from the top of the valve cover. its oily around the bottom too where it goes into the cover.

Edited April 1, 2019 by anderson1503

[Logan Lanfear]

Id start with your fuel pressure test.  Might as well get all the info before you try and diagnose. 

[2018GMC]

Have you replaced all 4 o2 sensors?  The 2 near engine tell computer how to adjust fuel mixture. The 2 after the cats will throw a check engine light if you have a cat that is plugged. 

 

Rockauto was the cheapest for Bosch sensors when I replaced sensors in my 1997. 

 

Have you cleaned the MAF sensor with carb cleaner, let air dry, then reinstall. 

 

Usually a bad fuel pump will cause a hard start or no start. Can also cause loss of power above 2k rpm.