Lbar

I would like some opinions. This is in my 05 CTS-V. I monitor my gas mileage and I noticed around the winter it started to decrease slightly, I wrote it off as winter blend gas. Back in early April I took a long highway trip and was about 12% under my usual highway average but I had put new tires on and sort of wrote it off again. In May I took a 4 hour trip and threw a P0175 on the ride back. I cleared it and it did not resurface.

As of a couple weeks ago it will throw a P0175 and P0172 fairly quickly depending on the style of driving. Steady highway trips provoke it. From what I can tell watching the live MPG (which is surprisingly accurate) it is getting too much fuel on light throttle input. Heavy/moderate throttle seems to be normal, as does idle/ neutral coasting.

I cleaned the maf correctly, the plugs (stock platinum) and wires have about 30k on them. Though the headers are probably harder on the wires. The car has a great tune which is has run for 2 years without issue. The fuel filter was replaced about 10k ago. Though well kept it has many miles, 173,000.

Old Geezer

iTrader: (3)

175K on the clock.... Have you changed the o2 sensors?

Lbar

Well, I know they haven't been changed in the past 35,000 miles, prior to that I don't know. Would seem odd for them to both go out? Or can one start to get weak and the computer will add fuel making both throw a rich code?

2xLS1

iTrader: (25)

It meand the LTFTs are more - than a calibrated threshold. Usually more - than -20%. Check for high fuel pressure. Could be a faulty MAF sensor telling the PCM there is more air than there actually is. And according to Motor Alldata, a problem with the EVAP system can cause those codes, especially an EVAP canister that is saturated will cause a rich condition.

Lbar

Just to update, after thoroughly cleaning the cone filter and a maf sensor recalibration all my problems have gone away.