Got Codes, any ideas where to start?

[IowaTahoe]

Well I bought a program thats called EasyOBDII that comes with the CD and device that hooks up to the vehicle to USB. Well it gave me 2 codes, P0171 and P0174. So the first thing I'm going to do is clean the MAF and check the fuel Pressure.

Anyone has any tips now that I have codes, please let me know.

Also, at idle the intake manifold pressure is 4.9psi, The program also was saying Lean on banks 1 and 2. But also something about Lean on the short, but the long was fine? Anyone know what I'm saying, whats this short and long?

 

[str8wkd]

This might held some.

LEAN TROUBLE CODES (P0171 or P0174)
A code P0171 or P0174 indicate the engine is running lean. This means there is too much air and/or not enough fuel. You can confirm the engine is running lean by looking at Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). Normally, STFT and LTFT should be plus or minus 8 from zero. If STFT and/or LTFT are more than about +10 or higher, it indicates the engine is running LEAN. Negative numbers (-10 or more) indicates the engine is running RICH.

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

______________________________--


Causes
A code P0171 may mean that one or more of the following has happened:


•The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor.

Possible Solutions
Possible solutions include:


•In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
•Inspect all vacuum and PCV hoses, replace if necessary
•Check for a dirty fuel filter and proper fuel pressure

 

[IowaTahoe]

Ok thanks, I cleared the codes and waiting for it to trip again. Nice thing about having this on the laptop is I can be driving it and I can watch the vehicle on the fly. If I remember right, STFT was in a area of -1.89 to -4.98 and Idle and LTFT was either + or - but it was like 21.29. When it happens again I'll do a screen shot.

So for right now I'm going to stick to cleaning the MAF, and I picked up a can of MAF cleaner. And I'm going to get my hands on a fuel pressure gauge.

 

[TunasTwins]

The LTFT carry a significant larger amount of "weight" in the injector pulse width calculation versus the STFT. Basically the trims show how much fuel the PCM is adding or subtracting to reach the stoichiometric burn rate of the fuel you are using. Normal gasoline or "E0" has a stoich air/fuel ratio of 14.68:1. Do your pumps have "E10"(10% Ethanol)? Well then the stoich ratio is around 14.1:1. The 02 sensors measure this and command the trims for the next time around, adjusting the BPW (injector pules width=how long injector is open) to reach the desired ratio. The short trims are more on the fly and the long trims are stored in memory. Think 65%LTFT and 35%STFT, maybe even more weight for the LTFT. Confusing? I've been trying to understand it for YEARS!

 

[IowaTahoe]

Well from what str8wkd posted for me, from what i gather is the LTFT shouldn't be higher then + or - of 10. and it is in the 21 area. and my STFT is like, 1.5 to 5.0 + or - so that seems to be right.

My question then is, if I know I'm lean at LTFT does that tell a trained mechanic really what to look for or is it just a throw parts at it is the only solution.

I still need to check fuel pressure.

It's kind of weird, I pulled the vacuum line from the FPR the other day and the HOE hasn't hestitated, nor has the gas gauge dropped like it has been. Keep in mind lately i've only been getting 8 to 11mpg. 140 to 160 to a tank. Right now I got 160 at half tank right now.

I'm kind of wondering if that vacuum line to the FPR wasn't on all the way. I'm still going to clean the MAF and check fuel pressure. I cleared my codes and waiting for the truck to trip again.

 

[BOSS]

You guys might be complicating this a bit...try the simple things first, quick wins ya know?


B

 

[IowaTahoe]

Actually I see nothing simple about it. Only way to still solve this is throw parts at it. I'm doing the simple things, like cleaning the MAF and I'm heading to Harbor Freight after work to pick up a FP test gauge. E-85 5.3's should be 48-54 psi. And I'll just go from there. The Hoe hasn't thrown a code in two days of driving, so I'm thinking the vacuum line from the FPR might have not been on all the way. Cause hesitation and poor gas mileage seems to have disappeared. Hoping all is fixed and it ended up being simple. but only time will tell.

 

[IowaTahoe]

Well I have 54 psi...so that seems good, with the FPR and fuel pump