Lean code/Rich mixture

[Derek Elmer]

The vehicle: 2001 GMC Sierra 4.8L Automatic

 

Trouble codes: P0300- Multiple misfire

P0171- Lean bank 1

p0174 - Lean bank 2

 

Symptoms: Stalls at idle, Black soot out the tailpipe, Stubles and misfires under load. Has burned a quart of oil since last oil change.

 

I have replaced the PCV valve, fuel pressure is fine, cleaned the EGR and replaced the intake manifold gaskets (did not change anything).

These symptoms have been intermittent over the last couple months but now it is worse than ever and is not going away.

If I unplug the MAP it quits. If I unplug the EGR nothing changes.

All of these symptoms are after warm up.

 

Any Ideas?

[Mr. Smith]

The vehicle:  2001 GMC Sierra 4.8L Automatic

 

Trouble codes: P0300- Multiple misfire

                      P0171- Lean bank 1

                      p0174 - Lean bank 2

 

Symptoms:  Stalls at idle,  Black soot out the tailpipe, Stubles and misfires under load.  Has burned a quart of oil since last oil change.

 

I have replaced the PCV valve,  fuel pressure is fine,  cleaned the EGR and replaced the intake manifold gaskets (did not change anything). 

These symptoms have been intermittent over the last couple months but now it is worse than ever and is not going away.

If  I unplug the MAP it quits.  If I unplug the EGR nothing changes.

All of these symptoms are after warm up.

 

Any Ideas?

 

<{POST_SNAPBACK}>

 

 

 

 

try cleaning your MAF sensor.

[99Silver6.0]

While the truck is running yank off your fuel pressure vacuum line at the intake. See if fuel pukes out of it.

[Mr. Smith]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

[Derek Elmer]

A couple more things to add: Unplugging the electrical connector on the MAF makes the truck run a lot worse. I am reluctant to clean it because it is so fragile and expensive!

Another thing, I unplugged the connectors on both upstream oxygen sensors and the truck runs great! Could it be that the cats are plugged? I am going to try replacing the fuel filter. Is it possible to clean the O2 sensors?

Thanks for the past replys guys, this is unbelievable how great people can help others out so easily!

[Mr. Smith]

A couple more things to add:  Unplugging the electrical connector on the MAF makes the truck run a lot worse.  I am reluctant to clean it because it is so fragile and expensive!

Another thing,  I unplugged the connectors on both upstream oxygen sensors and the truck runs great!  Could it be that the cats are plugged?  I am going to try replacing the fuel filter.  Is it possible to clean the O2 sensors?

Thanks for the past replys guys,  this is unbelievable how great people can help others out so easily!

 

<{POST_SNAPBACK}>

 

 

 

 

If it runs worse then it isnt the MAF. In your first post I thought you got the MAP/MAF mixed up. You can try carb cleaner on the sensors but I doubt that will help. Not sure but look up your 02 sensors and see if you can swap the front to back and back to front to see if your problem goes away.

[99Silver6.0]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

[99Silver6.0]

A couple more things to add:  Unplugging the electrical connector on the MAF makes the truck run a lot worse.

<{POST_SNAPBACK}>

 

 

 

No way!! Thats because the truck goes into SD!!

 

I have several spare O2's if needed.

[Mr. Smith]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

 

<{POST_SNAPBACK}>

 

 

 

 

No sense in being a tool is there?

[99Silver6.0]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

 

<{POST_SNAPBACK}>

 

 

 

 

No sense in being a tool is there?

 

<{POST_SNAPBACK}>

 

 

 

 

Why not, its a trend on here.

[Mr. Smith]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

 

<{POST_SNAPBACK}>

 

 

 

 

No sense in being a tool is there?

 

<{POST_SNAPBACK}>

 

 

 

 

Why not, its a trend on here.

 

<{POST_SNAPBACK}>

 

 

 

 

 

Must be for you...

[99Silver6.0]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

 

<{POST_SNAPBACK}>

 

 

 

No sense in being a tool is there?

 

<{POST_SNAPBACK}>

 

 

 

 

Why not, its a trend on here.

 

<{POST_SNAPBACK}>

 

 

 

 

 

Must be for you...

 

<{POST_SNAPBACK}>

 

 

 

 

Ive seen you do it quite a bit. Lets not be a hypocrite.

[Derek Elmer]

O.K.

You idiots need to grow up. I was just looking for some help and information on a problem that I have and I do not need you babys screwing up my post with this nonsense.

Thanks for the positive feedback that I recieved from you, but if that is all the information that you had then let that be it.

[Mr. Smith]

While the truck is running yank off your fuel pressure vacuum line at the intake.  See if fuel pukes out of it.

 

<{POST_SNAPBACK}>

 

 

 

 

This would not trigger a lean code. A lean code is triggered when the engine can't compensate for the excess oxygen seen at the O2 Sensors.

 

FPR would not in itself trigger a code. Only sensors monitored by the PCM will trigger codes FYI.

 

<{POST_SNAPBACK}>

 

 

 

 

No s**t! I didnt know that. PLEASE tell me more!!! I love to learn............

 

<{POST_SNAPBACK}>

 

 

 

No sense in being a tool is there?

 

<{POST_SNAPBACK}>

 

 

 

 

Why not, its a trend on here.

 

<{POST_SNAPBACK}>

 

 

 

 

 

Must be for you...

 

<{POST_SNAPBACK}>

 

 

 

 

Ive seen you do it quite a bit. Lets not be a hypocrite.

 

<{POST_SNAPBACK}>

 

 

 

 

My don't we feel superior? Since you feel the need to mess with me then go for it. I have let your pissant crap drone on and on. Frankly you show little in your shallow jabs. But you are getting boring. Your #2 try harder.

 

Hey Derek, the only idiot is you getting involved.