98 yukon 5.7l ping and P0171/P0174 codes

[oldyuker]

Hi, I'm new to this site and looking for help on my 98 Yukon 5.7 L 4X4. Original owner, 230,000 miles, basically maintained by myself, except for air and tranny repair.

Currently vehicle is pinging under load, never at idle, but without loss of power. Hesitates intermittently when starting from a dead stop. Also SES codes P0171/P0174 (system too lean right and left banks) in scanner.

NOTE: Above codes P0171/P0174 have been resolved: loose hose from valve cover to air intake line on right side.

Vehicle has fresh plugs, cap, rotor. Will replace fuel filter tomorrow. Tonight will check in dark for spark plug wire arcing.

There is much conflicting info on the web as to the resolution of this problem, but I've decided to throw out my problem since I'm stymied. I believe the pinging and the SES codes are related, but that's just a guess.

My other guess is an air leak past the MAF sensor. Is there a way of easily checking this out? Or even not easily? This is probably the problem as many posts in these forums have reported an intake gasket replacement for the 5.7L engine. I replaced mine at 160,000 miles.

I'm going to Sea Foam the fuel through the gas tank tomorrow to hopefully remove carbon deposits which can also cause pinging. Sea Foam tells me I cannot use their product through a vacuum line because of constraints on the Vortec engine.

This vehicle is in nice condition and I hate to junk it just yet. I may take it to a shop for particular diagnosis after I have exhausted all other avenues, or because I have found through this post it is the only road to travel. I have a read/erase scanner but nothing that will pinpoint plus or minus dist degrees, EGR and other sensor failures.

So, any help I can get from folks out ther would surly be appreciated.
Thanks in advance. Hope I provide enought info.

[maxwedge]

Low fuel pressure, vacuum leaks, bad o2 sensors, air getting in behind the maf, are all possibilites for a lean condition. I'd check fuel pressure first, you need 6065 psi at the port.

[oldyuker]

Yes, I did it yesterday. Fuel pressure was slightly over 60 psi.

NOTE: Above codes P0171/P0174 have been resolved: loose hose from valve cover to air intake line on right side.

Pinging is now the only problem, although it is harsh.

thanks.