Cadillac STS-V Series Forum Discussion, How sensitive to mods are these Vs? in Cadillac V-Series Forums; I have what I consider a pretty much stock V, the only thing I've changed was the air filter over ...
I have what I consider a pretty much stock V, the only thing I've changed was the air filter over to a K&N as it was cheaper than the stock paper filter, and the mufflers over to a Gibson system. Stock tune.
About 300 miles later I'm popping code P0174, Bank 2 Lean. Not much here on the board about that code so I'm wondering how common it is. I doubt it's the K&N as it's new and didn't have to be oiled and the factory doesn't saturate them like a lot of people do when servicing them. I'm aware the MAF is sensitive to contamination so I'm very careful when i do service the filters and they sit for a week to make sure they aren't saturated before I reinstall them.
It does seem the factory exhaust is pretty restrictive. Those 300 miles were all work commute (100 miles round trip) and I show a 2mpg improvment over what I could get out of her before the mufflers were replaced. And that 2 mpg was after getting stuck in slow construction zones all three days. I usually do get an improvement over the stock exhaust systems on my vehicles but considering the circumstances on the V, it seems I've gotten quite a bit more fuel economy than I expected.
Has something as simple as a muffler swap caused me to run lean? I don't think it's an intake leak as from the TSBs I've found on the net you almost always get a P0171 Bank 1 Lean with P0174, which makes sense to me.
Also, what kind of service life do you get out of O2 sensors nowadays? I used to replace them around 100K miles, (83K on the V now). It always seemed to bring back the fuel economy that slowly drops over the years, I'm guessing from contamination of the sensor.
Check all you intake connections. Somewhere you are getting unmetered air. Also get some MAF sensor cleaner and clean you MAF sensor. One of those two are causing your issue. I have 72K on mine and the original O2's.
As for the exhaust, the stock mufflers are the restrictive part. The exhaust itself is 2.5" mandrel bend pipes so there are no restrictions you get with crush bend pipes.
I have gotten P0174 without P0171 in testing the Spectre Intake. Check the couplers at the back of the stock upper intake.
Ah, and that brings up another question...
How do you get to that stuff? It appears you have to take the brace off but it looks like it's tied to the suspension to me, that I might need an alignment afterward. Does it disturb the way the struts are set right now?
I've got a set of shop manuals on the way thanks to KellyE, but they haven't gotten here yet.