2005 suburban 5.3 surging on highway under load

[Sstevieboy0208]

So I tried something that I found online unplugged the MAF and tried driving without it plugged to see if it fixes the problem but no luck. Still acts the same way. So I guess plugs and O2 sensor is next

 

[afpj]

You have live data scanner? What are your O2 sensors doing? Fuel trims? You said fuel pressure good...can you tell us what it was with key on, engine off, then engine on? Did you have fuel pressure gauge hooked up to see what's happening under load?

Just trying to diagnose before firing off the parts cannon. Re-reading thread it went from fuel to spark, but not conclusive to me.... hopefully much smarter folks can chime in as before.

 

[Sstevieboy0208]

You have live data scanner? What are your O2 sensors doing? Fuel trims? You said fuel pressure good...can you tell us what it was with key on, engine off, then engine on? Did you have fuel pressure gauge hooked up to see what's happening under load?

Just trying to diagnose before firing off the parts cannon. Re-reading thread it went from fuel to spark, but not conclusive to me.... hopefully much smarter folks can chime in as before.

I think it's due for tune up anyway. But since the O2 sensors need to be done in pairs I should do the other upstream one anyway