P0171+terrible gas milleage=??

[mstrmp3]

P0171+terrible gas milleage=?? **UPDATE WITH PICS***

'99 OHV

Ok, I have p0171 code ONLY, not p0174. I have terrible gas milleage and odd stutter when barely pushing gas pedal at certain speeds.

this is what has been replaced.

alternator
ECT sensor
coil
plugs (Motorcraft)
PCV valve
fuel filter

sugesstions?

cleaned maf sensor and throttle sensor.

 

[explorerguy89]

injectors?

 

[mstrmp3]

just injector cleaner only, so far... Is changing them out a PITA?

 

[imp]

just injector cleaner only, so far... Is changing them out a PITA?

Trouble with injectors almost always involves insufficient fuel delivery, not too much. Inadequate fuel injected does not cause terrible gas mileage. Replacing injectors not a PITA process. But rather expensive. How many miles are on the present injectors? If problems develop with injectors, it is most usually just 1 or 2 involved, not all of them, unless somehow a whole bunch of gunk got admitted into the line, which is very unlikely. Occasionally, injectors do get gummed-up by carbon/oil deposits, resulting from combustion products backing up due to bad intake vale(s); again, rarely ALL of them.

O2 sensors replaced? How many miles on them?

Fuel pressure checked?

Just a few thoughts.......imp

 

[mstrmp3]

injectors and O2 sensors are stock (151K) miles. There is a strange smell in the exhaust, almost like unburnt fuel.

BTW the IAC was replaced as well.

 

[manaen]

Did you check for a vacuum leak on bank 1?
Did you check your Fuel Pressure ?
Did you read your plugs to see if it is one specific cylinder that is lean?

I would start with those and then move on.

 

[imp]

Did you check your Fuel Pressure ?
Did you read your plugs to see if it is one specific cylinder that is lean?

I would start with those and then move on.

The point here is that, since there are not O2 sensors for each cyl., one cyl. running lean (due to clogged injector) will be interpreted by O2 sensor as overall not enough fuel being delivered, so fuel delivery may be increased, causing actually too much. imp

 

[ThePhoenix]

try your fuel filter

 

[BobWiersema]

The point here is that, since there are not O2 sensors for each cyl., one cyl. running lean (due to clogged injector) will be interpreted by O2 sensor as overall not enough fuel being delivered, so fuel delivery may be increased, causing actually too much. imp

Exactly, it thinks its lean so it adds more fuel and is actually burning rich. Clean the MAF and check the PCV and air filter. If all looks good I would replace the O2 sensors. Thats a lot of miles on original sensors.

Bob

 

[mstrmp3]

Ok, replaced the MAF and TPS sesor last Sat. Filled her up with gas and now I get GREAT gas milleage. Twice what I was getting before! I have driven it about a week now with about 200 miles since the sensor changeout...but then....

This morning when I started the truck I get P0171 and P1131!! DAMMIT!! This weekend I'm going to change EGR, EGR solenoid, and upper intake seals. I'm also going to check wiring to O2 sensor. Which side is bank 1 on? drivers?

 

[BobWiersema]

Bank 1 is passenger side. Bank 1 is always the side that cylinder #1 is on.

Those two codes point at Bank 1 sensor 1 acting lazy. I would replace that first.

Bob

 

[mstrmp3]

I'll replace the O2 sensor next. I checked the codes again (without resetting them) and the P1131 code is gone, just the P0171.

 

[mstrmp3]

Update

I replaced the upstream O2 sensor and while the tire was off, I rechecked my bank #1 plugs (1-3). I have included pics of them. How do they look? only about 1K miles on them. (Motorcraft plugs)

1st here is the old O2 sensor
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer007.jpg
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer006.jpg
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer005.jpg

now cylinder #1
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer011.jpg
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer010.jpg

cyl#2
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer009.jpg
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer008.jpg

cyl#3
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer004.jpg
http://i197.photobucket.com/albums/aa180/CPUFIXER/public/explorer003.jpg