Dukenukemx

Check engine light came on the other day and it was for p0171. I checked the MAF and cleaned it with mass air flow cleaner but it was pretty clean already. I cleared the code and didn't come back but I'm wondering what could cause the code?

My Vette has over 85k miles and it's getting poor gas mileage. I decided to order a couple of front Denso O2 sensors cause I heard they can get lazy. Now I'm wondering if I should replace the MAF? I drove it around a couple of days and nothing came back.

If replacing the front O2's work out great I'll replace the rears as well.

BigGun

Rears have nothing to do with that code. If you have a problem with the rears it will set a code. Check the connector and wires at the map for loose connection or exposed wires.

Dukenukemx

Map sensor can cause Maf sensor code?

BigGun

A small vacuum leak can set this code although usually accompanied with P0174. Check all the connections after the maf to the throttle body and make sure they are tight and not leaking. The pcv lines also need to be checked for small holes or leaks as this is a common problem area.

tblu92

P0171 says nowhere specifically that it is MAF related---A lean code would isolate the left bank from the right bank--- P0171 indicates a lean condition everywhere---Here is the best site for diagnostics----According to it-- it indicates a low pressure or low fuel flow issue---Related to a clogged fuel filter or failing fuel pump--- read this about 1/2 way down under diagnostic aids

http://www.gearchatter.com/viewtopic10475.php

PS also nowhere are 02's mentioned as a problem----Remember only the front 02's control P/T engine fueling and the rears are only there to report the condition of your cats

BigGun

The code P0171 indicates a lean condition in bank 1 per 1999 C5 dic code lists. P0174 indicates a lean condition in bank 2. On my 99 this code was set when the pcv line connected to the left hand side valve cover popped out. I also discovered a small hole in the line near the throttle body where the pcv valve is located which is a common problem.

Dukenukemx

I'll check the PCV line when I get the O2 sensors.

tblu92

Lean codes that separate the left from right banks are always related to front 02 issues where the ECM can determine left from right
A lean code that is NOT 02 related is either MAF related or fuel pressure/flow related and cannot isolate left from right but lean in general that affects BOTH sides

BigGun

I don't think there is a code for "lean in general" on a C5. Just for left and right bank, two separate codes. Are you saying that because the code indicated only a lean bank one that the O2 is the problem?

Dukenukemx

I think BigGun is right cause I found this broken and cracked. Would Autozone have this? Don't know what it's called. PCV sits in there.

BigGun

You can use standard pcv hose of the appropriate size. You don't need the fancy collers on the original. Probably a dealer part if it is available. The pcv valve is standard.

Dukenukemx

I decided now's a good time to install a catch can. I ordered one off Flea Bay for $20 and will install it. I did find a lot of oil in my throttle body.

tblu92

Didn't mean that in exactly -- But a code from P0171 thru P0175 are lean /rich codes that do not mention your 02's--- Just rich or lean period bank 1 or 2
Typically they mean that he lean condition is NOT 02 related -- if so you would get a lean/rich code that mention your 02's-- like P0135--so if it is not 02 related then all that it can be is a MAF sensor--low fuel flow or pressure or an imbalance in fuel between the left and right banks--- or most often an exhaust leak on the side that's LEAN---

Dukenukemx

Well I did replace all 4 O2 sensors over the weekend. Not an enjoyable experience. The fronts were a little black but the rears were totally black. I wonder if that's a symptom of a rich fuel mixture? Might explain my poor MPG I've been getting lately. BTW if anyone is wondering http://www.ebay.com/itm/131489103493?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT