2002 Workhorse W22 with 8.1L Vortec and Ally 1000 drivetrain 53K miles

[penman39]

Today I changed the plugs and wires and cleaned the MAF on Alice. After I was done, I hooked up my OBD reader to look at some live data. I didn't drive it anywhere just idled and also hold at ~1500 RPM. At either idle or 1500 my Bank 1 O2 sensor would bounce from .1xx to 6xx while the Bank 2 sensor went from .4xx to .6xx . This doesn't seem normal to me. Do you think I have a bad sensor and if so what brand do you recommend replacing with. On AdvanceAuto they vary from $95 to $250 (gulp).

I have attached a picture of the new NGK wires installed and also the old plugs laid out in cylinder orientation with plug 1 top left and plug 8 lower right. Odd plugs on left, even on right.

 

[wae]

Could mean that bank 1 is running a little lean, but that could be "normal".

When it's bogging down out there, is it in open-loop or closed-loop mode?  Typically WOT is processed in open-loop, so it's not really paying that much attention to the O2 voltage.

What are the STFT and LTFT numbers?

I know absolutely nothing about that particular transmission, but are they known to have any torque converter lock-up problems?  I've seen some rough running when it can't unlock as the engine speed drops, and there are some boxes that are known to do that - not sure about the Allison.

Just thinking it through, it sounds like the problem is when the engine is low-to-middle rpm, high load, throttle butterfly mostly or all-the-way open?  If you pull away from a stop sign at full throttle does it go as much as a motorhome will go or does it bog out in that situation?  When it's struggling to downshift, what happens if you manually pull the lever back a position? 

 

[Isaac-1]

On a side point have you checked your fuel pressure and your fuel pressure regulator for leaks?  The 8.1L does not have a fuel pressure sensor, so it makes all its calculations assuming the fuel pressure is in range 55-62 psi with 58 psi being optimal

 

[penman39]

On a side point have you checked your fuel pressure and your fuel pressure regulator for leaks?  The 8.1L does not have a fuel pressure sensor, so it makes all its calculations assuming the fuel pressure is in range 55-62 psi with 58 psi being optimal

That I have not done. Is the pressure regulator in the engine bay? If so, I don't think it is leaking since I don't smell any fuel.

 

[Heli_av8tor]

Mine is built into the pump in the fuel tank. Yours may be on the fuel rail. They changed location early 2000's.

 

[garyb1st]

Mine is built into the pump in the fuel tank. Yours may be on the fuel rail. They changed location early 2000's.

I guess when they built these back in the day they just assumed everything would last for ever.  Hope you don't have to replace yours. 

Tom do you have a scan gauge?  Also if you do, how many of the things on this thread can be checked with it.  For example, will it check fuel pressure or fuel trim?

 

[Isaac-1]

Carl, yours should have one, the change in design was done around 2004 or 2005.  The fuel pressure regulator should be at the very back of the drivers side fuel rail.  You would not notice a leak without inspecting it, as it is vacuum operated and the leak would be in the diaphragm being sucked into the vacuum line, which would then enter the engine as unmetered fuel.  The schrader valve pressure test port is towards the front of the passenger side fuel rail, you will need a fuel pressure gauge with the right size fitting (common to GM vehciles of the era, Ford used a slightly different one) to check it.

 

[Heli_av8tor]

Gary, I have a WiFi OBD adapter and have used various apps. I can monitor fuel trims. Fuel pressure is not available as there is no pressure transducer on this engine. I have checked mine with a test set borrowed from Auto Zone.

 

[garyb1st]

Thanks Tom.  I'll have to check if ours will do what I want. 

 

[penman39]

I finally got the motorhome out for a little run because I had to get it inspected and I hooked my diagnostic tool up and here are some readings. The fuel trims look Ok to me.

 

[drisley]

This issue sounds familiar and I have pretty much the exact same chassis, on a 2002 HR Vacationer.

When we were our west in 2018, I had numerous instances where the engine seemed to be missing when trying to climb hills or otherwise under load. It was as if the rig was bucking up the hill. I did everything I can to figure that thing out. Cleaned the MAF, changed air filter, changed fuel filter, yada yada. Even had a guy come out with his fancy diagnostic computer and he couldn't find anything wrong. Mixtures fine, cylinders firing fine. The issue ONLY happened when it was under load, usually climbing a hill. I just learned how to baby the gas pedal to sort of keep it happy.

As I came back east again, the problem totally disappeared. Even as we dropped in elevation and it wasn't so darn hot, the problem went away.

Since then, we were in the Smokies last year and I climbed some hills that were much steeper than some of the ones out west, and the rig went right up the hill no issues.

So, basically, I chalked this up to a combo of altitude and heat. The thinner air at altitude combines with desert heat out west... and the Vortec just didn't care for it. Down down in elevation some and a nicer temperature, and it is no issue.

For what it is worth. You didn't mention where you were driving around.

 

[Arch Hoagland]

This issue sounds familiar and I have pretty much the exact same chassis, on a 2002 HR Vacationer.

When we were our west in 2018, I had numerous instances where the engine seemed to be missing when trying to climb hills or otherwise under load. It was as if the rig was bucking up the hill. I did everything I can to figure that thing out. Cleaned the MAF, changed air filter, changed fuel filter, yada yada. Even had a guy come out with his fancy diagnostic computer and he couldn't find anything wrong. Mixtures fine, cylinders firing fine. The issue ONLY happened when it was under load, usually climbing a hill. I just learned how to baby the gas pedal to sort of keep it happy.

As I came back east again, the problem totally disappeared. Even as we dropped in elevation and it wasn't so darn hot, the problem went away.

Since then, we were in the Smokies last year and I climbed some hills that were much steeper than some of the ones out west, and the rig went right up the hill no issues.

So, basically, I chalked this up to a combo of altitude and heat. The thinner air at altitude combines with desert heat out west... and the Vortec just didn't care for it. Down down in elevation some and a nicer temperature, and it is no issue.

For what it is worth. You didn't mention where you were driving around.

Did you change the spark plugs and wires?

 

[Isaac-1]

I find my 8.1L really does not like that 85 and 86 Octane gas they have in some of the mountain states, if I run 87 or higher it is happy.

 

[penman39]

For what it is worth. You didn't mention where you were driving around.

Just in Western PA. My elevation is less than 1000ft above sea level. I was looking for confirmation that my fuel trims were OK. I'm still suspicious of the one O2 sensor. What's a good price and place to get a new one??

 

[Isaac-1]

For O2 sensors I suggest going with OEM GM Delphi

 

[penman39]

I finally got the motorhome out for a little run because I had to get it inspected and I hooked my diagnostic tool up and here are some readings. The fuel trims look Ok to me.

Went camping this week and the engine ran flawlessly. No issues whatever. The fuel trims all looked good. The only thing nagging at me was the Bank2 O2 sensor bouncing around as before. Bank 1 was fairly steady at the same time.