98 eb 4.0 code help.

[ditchwitch1]

Hi,My '98 EB,4.0 sohc 155k has developed a code problem,I finally got it running good,and figurerd out through using the trip odometer that I get between 19 and 22 mpg,depending on my foot.Anyway,the check engine light recently came on,I bought a code scanner with diagnostic capabilities,and pulled the codes,I get 2, P0171,and P0174,{lean bank 1,and lean bank 2}after doing some research on web,found these to be indicative of restriction in fuel system,where not enough gas is making it to combustion.It runs too good,and light is coming on even at low speeds or even at idle.Full tuneup recently done,including o2 sensors and fuel filter.I cleared the codes,and I am good for about 1 1/2weeks,then light comes on again,reset,and same thing over.Has anybody else ran into this?What would be the next logical step?Thank You in advance for any help,info,or suggestions you can offer.

 

[oplitic]

Figured I'd do a little searching and try to give ya some help...

What it means, symptoms, causes, possible solutions...

http://www.obd-codes.com/trouble_codes/generic/p0171-system-too-lean-bank-1-oxygen-sensor.php

This one is about a chevy, but his problem is kinda the same, he just replaced his o2 sensors, a poster had some ideas...

http://www.obd-codes.com/forums/2693-obd-codes-p0171-running-lean.html

Most people are saying to clean the MAF, make sure there's no vacuum leaks(usually at the intake), incorrect o2 sensor, etc.

 

[ditchwitch1]

RE:98 EB code help

Thanks,I will check those sites out.I do notice hissing from outside truck when it is idling,wasnt sure if it was belt noise when cold or what,but vacuum leak may be culprit{I hope}Thank You again for your quick reply!I am glad I have you guys.Kurt.

 

[ExploringNC]

If it hasn't been done yet you need to have the manifold gaskets replaced. Banks running lean is a sympton of the manifold gaskets sucking air threw.

This should give you all the info you need Intake Manifold Gaskets - P0171 & P0174

 

[manaen]

there are a few things that can cause this,
1) vacuum leaks in the lines and/or manafold gaskets
2) Dirty MAF
3) Low Fuel pressure

#1 - this is obvious check for vacuum leaks and make sure all the lines are good. You can use propane to check for leaks, it is much cleaner than the carb cleaner trick (and safer)

#2 - this should be done anyway as regular maintanence

#3 - this can be caused by dirty fuel filter, bad fuel pressure regulator (FPR), or bad fuel pump. You need to check the pressure at the rail to make sure it is up to spec. If you have a returnless fuel rail the pressure should be around 60psi (yeah you read that right), if your fuel rail has a return line it should be around 35psi. The returnless system has the FPR located in the tank with the fuel pump. The other has the FPR on the fuel rail.

check those things and get back with us