>> LEAN both banks, P0171 & P0174, FTrims WAY positive, O2 sensors "bouncing" full range!...

[bills4065]

try spraying some soapy water around that breather hose connector at idle and see if it is leaking.

 

[bills4065]

I am surprised your check engine light is not on with exhaust gas as lean as your numbers show.

 

[fixizin]

I am surprised your check engine light is not on with exhaust gas as lean as your numbers show.

Oh, CEL/MIL IS ON... sorry if that wasn't apparent.

So, with manually pulling vacuum on the EGR, what's the drill here, engine COLD, WARM, etc...???

 

[bills4065]

What code or codes is the truck throwing?

 

[bills4065]

With P0171 and P0174 the first thing to do is what I said earlier. Graph your 2 upstream sensors at wide open throttle and ensure they both go full rich above 800 millivolts. If they do this eliminates a fuel delivery problem.

 

[fixizin]

With P0171 and P0174 the first thing to do is what I said earlier. Graph your 2 upstream sensors at wide open throttle and ensure they both go full rich above 800 millivolts. If they do this eliminates a fuel delivery problem.

Does manifold pressure matter, i.e. in gear and under load vs. parked in neutral?

PS: why should the mixture be "off" in the RICH direction just because of WOT? Just revving to 3,000 RPMs greatly improves the Fuel Trims (see above), wouldn't fuel delivery/starvation issues start to show there...? #LearningOTJob #Where'dIPutThatOldCarburetor?

 

[SenorNoob]

WOT unloaded, you're gonna hit the rev limiter or overrev real quick.

PCM is usually programmed to be rich at WOT to help prevent damage from lean...

 

[bills4065]

The test I am talking about has been used for years by automotive instructors! Every gas engine runs rich pedal to the metal. The oxygen sensor is not used at wide open throttle,but it still produces a signal you can use to tell you something. If at wide open throttle both of your oxygen sensors are above 800 millivolts you DO NOT have a fuel delivery issue. You do not have to speed to graph this-pedal to the floor first and second gear will tell you all you need to know. I have checked lots of vehicles with this test.

 

[Blmpkn]

I'm relatively sure I read a thread awhile back where Ron was chasing a double bank lean issue... And he eventually figured out that he had his o2s plugged in backwards