Vortec 454/4L80e HD swapped 1999 Tahoe OBS

[bigfootchiro]

If I'm you, I'm looking for a fuel problem on bank 2 for starters.

Only thing fuel related on Bank 2 specifically would be injectors then, correct? Maybe O2?
Keep in mind, this is a 454, and is not like the injector setup on the 350s.

 

[randeez]

could be ...engine usually runs in open loop when first started (not looking at o2 sensor) that could be why when you turn it off and back o nit runs fine

 

[bigfootchiro]

could be ...engine usually runs in open loop when first started (not looking at o2 sensor) that could be why when you turn it off and back o nit runs fine

So funny you say this, because it made me look at the readings at cold startup... as soon as it hit 110 degrees, the O2 sensors start kicking in. What do you make of this? Bank 2 LTFT 5.5% at start and big differences in voltages

 

[swathdiver]

So funny you say this, because it made me look at the readings at cold startup... as soon as it hit 110 degrees, the O2 sensors start kicking in. What do you make of this? Bank 2 LTFT 5.5% at start and big differences in voltages

View attachment 225239

You're narrowing it down, good thinking and observations. Now, what do those two mean? Too rich, not getting the cats hot enough? Or the opposite, I always forget which is which, like these <> in math!

 

[bigfootchiro]

You're narrowing it down, good thinking and observations. Now, what do those two mean? Too rich, not getting the cats hot enough? Or the opposite, I always forget which is which, like these <> in math!

Damn math. I used to be good at it! Positive numbers mean lean condition, like vacuum leak, clogged injectors, not enough fuel, etc. Right now I have no cats, and practically no exhaust lol. Pipes are dumped right next to the transmission.

 

[randeez]

that bank 2 sensor is way to low they should oscillate from like .700 to .999

 

[swathdiver]

Alright so you're lean on that side for some reason, O2 sensor is not getting as hot as the other side.

So what can cause this? Leaks, cracks, crimps, air, fuel, shorts to ground? Fuel getting to both sides of the rail evenly? No pipes crushed? Injectors good and nothing falling off them or has fallen into the hole they drop into? Intake gasket good, no cracks or leaks on that side, head gasket, intake gasket, intake manifold, cylinder head? Plugs screwed in all the way and firing? Not stripped and leaking? Rockers, valve seals...

 

[RST Dana]

Maybe swap injectors from one side to the other? See if the issue changes sides as well.

 

[bigfootchiro]

Alright so you're lean on that side for some reason, O2 sensor is not getting as hot as the other side.

So what can cause this? Leaks, cracks, crimps, air, fuel, shorts to ground? Fuel getting to both sides of the rail evenly? No pipes crushed? Injectors good and nothing falling off them or has fallen into the hole they drop into? Intake gasket good, no cracks or leaks on that side, head gasket, intake gasket, intake manifold, cylinder head? Plugs screwed in all the way and firing? Not stripped and leaking? Rockers, valve seals...

I would sure hope it’s not a head or valves... that’s what happened last time to the 350! Intake gaskets are all new, but doesn’t mean they aren’t leaking. There’s definitely a lot it could be, so time to start narrowing it down! Thanks man!

Maybe swap injectors from one side to the other? See if the issue changes sides as well.

That’s a good idea too. I’ll have to try that. Just swapped the O2 sensors around to see if it follows. Here we go!

 

[bigfootchiro]

Initial startup after O2 swap over. Long term in 2 is still 5.5 but 1 is 3.9.



Mid-warmup: as soon as O2 sensors go into closed loop (around 110), Bank 2 starts shooting up quickly to 25%. Short term on 2 is still not the greatest.



Full warm up: short terms stabilize, long term on 2 is still 25%. When RPMs go up to around 1800-2000, Long Term on 2 drops to around 9-10. Hit it with a load after that and it goes up to around 12.5%. Also, STFT on 2 is pretty erratic. It will stabilize, but say I come down to idle in Park or moving, it will go up to around 9-11%, then take about 10-20 seconds to stabilize, whereas Bank 1 stabilizes immediately