Need advice on Chevy 8.1 Vortec engine (2003)

It only takes a few minutes to change the CO sensor, and probably they did not have yours in stock in a small town like Moab.

Have you been filling up with 'regular' gas? IT can be 85 octane in Moab area, and anyplace that is over 5,000' elevation. Try filling with (gulp) 91 octane or higher and see what that does for you. It might be that the knock sensor was hearing something and went to the low power mode because of the low octane gas.

Higher octane fuel will provide much better MPG. 85 octane might be fine in Denver, but as you leave the higher elevations, and as you try to climb a steep mountain, you really do need 87 octane or higher fuel.

It only took me a few minutes to change my O2 sensor in my Dodge van. the one on my motorhome was really easy, and all I needed was a 7/8" wrench. The Dodge required a special tool, Napa has a couple of designs that cost only $6.95. Ask at the counter.

Good luck!

Fred.

Limp mode?

Had the exact same problem over a period of about a year, got worse gradually.

Changed the fuel filter and Oxygen sensors. No help.

Type of fuel won't change it either.

Cleaned the MAF sensor...problem cured.

The O2 sensors were detecting that the air to fuel mixture wasn't right and set the check engine light.

What code are you getting for the Check Engine Light?

I was getting P0150 and P0151 codes.

Al, Knowing that you are not proficient with tools. I would suggest you take it in to a truck service center near you. You can find one here as I'm not familiar with any of them personally in your present location however any good truck stop should be able to take care of you.... www.rvservicesreviews.com

codes are PO131 & PO151

We've been through Moab many times with our 8.1L engine and at a little over 4000 feet in elevation, the octane of the fuel would not be a problem. Since the O2 sensor was changed, that should eliminate it as the problem, unless the lead to it came loose. A bad O2 sensor usually results in very poor fuel mileage as well as the check engine light coming on. Your exhaust pipes also would probably be black from running rich.
I would try to take the coach to a place that can check your emissions. If either the MAP is dirty/bad, or if one of the sensors is bad, it will show up in your emissions being well out of spec. If the shop does not have the capability to check emission, the best they can do is throw parts at the problem, at your expense, and see if a test drive feels different from the last test.
Keep in mind that the 8.1L engines, in SOME coaches, had a problem with the rear spark plug wires deteriorating, due to heat. This can also cause a loss of power if one or more cylinders are not firing properly, which causes your engine computer to try to adjust to the situation. If your coach is one of those where the manufacturer did not allow enough air flow it may mean that you will have to install a set of high temperature silicone plug wires, like the Taylor Extreme silicone plug wires with the additional heat shield.

2 other codes as well : PO120 Throttle Position Sensor switch A and 220 throttle position B

We have not had the 02 sensors replaced yet.

As others have said, a faulty MAF sensor reading or an exhaust leak can simulate the conditions required to set an O2 sensor code.

Also any replacement O2 sensor must be of OEM manufacture or your ECM make conclude that the others are now faulty.

It's highly unlikely that the throttle positions codes are related to the 02 codes, when the conditions which set those codes degrade further you could experience an "idle only" condition. Here's why.

GM has a redundant throttle by wire design on these LS era engines to help eliminate the possibility of untended acceleration. The down side of their design is that if the 2 don't completely agree the throttle body will not open and you will have a dead pedal.

If the miles are under 100K it's usually a faulty throttle body.

Clean the MAF sensor, replace the air filter, clears the codes and cross your fingers.

I went through the same problem - random codes. Service center finally replaced MAF sensor
which fixed problem ?

The 02 sensor will get slow and kill performance. By the time it finally throws a code it has been bad for some time. He should have replaced it.