Remove the belt? Wont work without the belt... No alternator, no water pump etc. Or am i reading what you mean wrong.

 

Is it all one belt or is there a different belt for the air pump. They use to run a small belt just for the air pump. Do you have a air pump? Do you have a 02 sensor before the cat and after the cat?

 

The OP's truck is a 1990, the O2 sensor is before the converter.

 

There is a listing for pre and post 02

 

Wherever you found that listing it's wrong. Post converter O2 sensors were not used on this vintage truck until OBD-II was implemented. On gas engine trucks this is generally accepted as 1996.

 

Looks like its just one serpentine belt for the whole thing, not v belts. From what I can see when i was changing the o2 sensor is that there is just one, and its before the cat, on the H pipe.

 

What im trying to figure out is can EGR malfunctions cause a lean condition? I know i need to fix the egr stuff but im trying to take care of the lean issue first.

 

I would fix first what you have found wrong first. A lean code could be just about anything, vacuum leak, injector, air pump. Like I said the egr uses exhaust gas to lower box and combustion temp for NOX. It's makes the air fuel richer less air. For a lean code you have to have all component working. Did you mist some water to check for vacuum leaks. There are other products you can use but water is safer

 

Ok I will check all that out. Thanks a bunch for your help. I just want to make sure you're aware its not just the lean code being thrown, It actually is running lean which i determined from the spark plugs being white when i changed them out to put in some motorcrafts. What does the water mist do to help locate vacuum leaks? Just wanna make sure im doing it right.

 

You guys talk about fuel pressure yet? if so I missed it, what is the fuel pressure reading?

 

If you use a spray bottle go around the intake the water will seal the vacuum leak of a couple of seconds. I also great at finding bad wires, if just find it easier to fix what you have found wrong with the truck. Then move on to the next step, it's hard finding problems on the older trucks with out live data. Spray around intake, vacuum lines, EGR, make sure iac is working.

 

33 at idle after i replaced the regulator. was at like 74ish idle

 

Thanks man ill get to work and report back

 

Oh yea sorry I did read that earlier on in the thread.

+1 with Conanski suggestion.

Disconnect the AIR hose from the AIR pump so that secondary air is bypassed to atmosphere during test, run the KOER test again see if code 41 disappears.

Should able to disconnect and plug the vac line to the diverter valve but that may be the sourse of the problem. Failure of the valve, its stuck, or someone rerouted vacuum lines as so it always has vac to it even when shouldn't have. Secondary air dumped to atmosphere = no vacuum supplied to the diverter valve.

Disconnecting the hose at the pump itself ensures that no air is delivered to the engine for accurate test result.

If code 41 disappears hose disconnected from pump the secondary air system is source of the problem know to look to it find fault.

If code 41 remains it is not the problem, reconnect hose move on.

 

Makes allot of sense, thanks man! I will do that in the morning and post the results.