I have a 1999 k1500 obs 350 spider injected with the engine and trans out of a 98 with less than 150k on both....when I lay on the throttle it'll shift nice but the engine stumbles like its gettin to much air and not enough fuel or vise versa then after a couple seconds she'll get up and go like normal. I have codes for low voltage on o2 sensors and spark plugs on cylinders 1,5, and 7 have a big white spot just like they're is no fuel or not enough fuel getting to the cylinders. The o2 codes have always been there and this problem just started recently so could it be the injectors, fuel pump, or something else? Any help is greatly appreciated

 

Post the codes here. Have you checked your fuel pressures yet? Have you cleaned your MAF sensor at all?

 

like stated post the codes and try unplugging the MAF

 

I cannot stress it enough. I just rebuilt the top end on a 98 Vortec 5.7L because the intake gaskets were blown...
If you no nothing about the engine expect these to be bad.
Also, check the coil tower (pics in profile)
If you have a K&N air filter, to much oil will cause a dirty MAF and you'll need to clean it. Just a slight pink hue to the air filter keeps it ok.

 

 

You should clean the MAF. I mean its very easy to do so why not? At least you eliminate that issue. You can even clean it with rubbing alcohol, but you'll have to let it dry out good before you use it, as it doesnt evap out fast like MAF cleaner does.. Pretty sure you can rent a fuel pressure guage at most auto part stores like Autozone, ect.

As for the intake gasket leaking, you can spray some WD-40 on it, If it clears up, its bad, if not its easy to clean the WD-40 off. I've known guys to use gasoline to do this but that's a bit dangerous and not a good idea at all, but a leak will speed the motor up. Might want to hook up a vaccum guage and see if it stays steady too. If not you have an issue with a leak or something similar.

 

I’ll do the WD-40 trick and clean my MAF sensor this weekend...I went to buy a new fuel pump last weekend but I didn’t know which one to get does it matter what the GPH are?

 

The main thing is that your fuel pump is putting out enough pressure to the fuel pressure regulator. Technically, I believe the fuel pressure for your vehicle is 60 PSI, but am pretty sure range can be 55 to 62 PSI or so. If you decide to change it out, my personal belief is to stick with a stock AC Delco unit, But Delphi's are supposed to work well.

 

Update: changed the fuel pump with a precision brand and the fuel filter with micro guard from Oriellys and it fixed it for the most part. Pulled the spark plugs and checked them 3 are bad so just gonna do another complete tune up with better plugs, wires and cap