Chasing OBD2 codes for inspection

[blue96]

Look, before you guys get all:

You must be registered for see images attach

..hear me out!!

Ive failed inspection because of codes P0171 & p0174. Both banks are showing a lean condition. My first instinct was look for vaccum leaks (none found) change the upstream o2 sensors and/or check the fuel pressure.

Here is information that may apply to this:

1) changed the fuel pump/strainer/filter about four months (1500 miles) ago

2) cleaned MAF last month

3) exhaust has a few leaks but downstream from the rear o2 sensor

4) intermittent coolant leak from an unknown source on front of engine*


#4 is the reason I started a new thread.. Is it possible that the infamous intake gasket leak could throw the "lean banks" code(s)? This very repair was done about 8 years ago and I'm wondering what y'all think:

Should I pull the trigger and change the gaskets??

 

[1997chevydriver]

Normally when the gaskets go it dumps coolant internally into the oil or externally in the corners of intake mani.

Easy way to check to see if there are any internal vac leaks is to block of PCV hole, vent in pass valve cover to intake tube and put your hand over the oil cap hole. If you feel pressure your gaskets are not sucking air from the inside of the motor.

I would definatly check fuel pressure... Could be that the spring in the regulator has become weak and is not sustaining corect pressure

Also if the intake gaskets are leaking OUT of the motor I would still change them to prevent future problems.

 

[SAATR]

A MAF system will show a lean condition if "extra" air gets in anywhere after the MAF, so your search should also include intake piping, PCV and crankcase air supply hoses, and all vacuum hoses and gaskets. If the intake leak is to the inside of the motor, it shouldn't cause a lean condition as it is sucking in metered air, which should not affect the A/F ratio. Of course it can cause a plethora of other issues, like a poor idle and an individual cylinder + random multiple misfire. In all honesty, if you suspect a leaking intake gasket I would change it, regardless of the lean condition. Those can escalate quickly and without warning, in a single drive cycle. Disassembling the intake manifold will certainly help in eliminating possible vacuum leaks, and will allow you to inspect (and clean!) the LIM, upper plenum, throttle body, etc. That's the option that I would take. If it returns, then you have other things to look at, like your MAF or FPR.

 

[blue96]

Thanks for the information guys, I'll look further into this after work tomorrow.

Saatr- Loo E Z an uh I hate it when people call it Loo Z an uh or lousyanna lol... I live just north of Baton Rouge.

You must be registered for see images attach

 

[SAATR]

Yes sir! I'm out of Minden, which is west of Shreveport on I20.

 

[blue96]

So, I looked for "tell-tale" signs of the intake leaking coolant and found none. Also, I left my headlights on this morning and needed a jump start to leave work. Whats that got to do with anything? I noticed afterwards the SES light never came back on and the truck ran a bit better. What the F?

Also, Im going to remove the air intake to take a peak in side the upper intake plenum. Oh, is there any benefit to removing the "cup" from the throttle body butterfly? I did that on a Sonoma back in my Minitruckin' days and it was an "automatic race truck" afterwards. Young and dumb lol

 

[blue96]

Should this vacuum port be open or am I missing something here??

You must be registered for see images attach

 

[SAATR]

That's normal.

 

[blue96]

Well, new upstream o2's and....

You must be registered for see images attach

Dammit!

 

[blue96]

Easy way to check to see if there are any internal vac leaks is to block of PCV hole, vent in pass valve cover to intake tube and put your hand over the oil cap hole. If you feel pressure your gaskets are not sucking air from the inside of the motor.

I did that and felt pressure.. Going to check fuel pressure next.