Ok, so about 2 weeks ago I had a tune up, as my 2010 Maxima was at 112,XXX miles.

They changed the spark plugs and "cleaned all the buildup out of the intake side of the engine". The shop reported the spark plug tubes had oil in them and they recommended replacing both sets of valve covers as the seal itself was not serviceable. Car has been running great for the past 2 weeks until yesterday I noticed a slight burning oil smell when parking my car after driving. The smell was very faint and there was no visible smoke and I only smelled it outside of the car. On my next drive the "Service Engine Soon" light came on and the car still runs terrifically. The very faint burning oil smell is still only detectable outside of the car and I see no smoke. Since the light has come on the car is idling higher and when I am driving, if I let off the gas, the rpms actually go up slightly. I had a parts store pull the codes for free and I am getting P0171, "Bank 1 too lean"

My first thought is that when they removed the intake and valve covers to do all the service work they failed to seal them adequately upon reassembly. If there were a vacuum leak related to the work I mentioned above, do you think my engine would be running flawlessly? Or should I notice a rough idle or lack of power or anything?

Just trying to arm myself with knowledge before returning there and them wanting to replace all the O2 sensors...

Any suggestions?

Thanks!

 

You don't have to replace all the O2 sensors, just one. P0171 is for the bank 1, sensor 1. Bank 1 is the side of the engine by the firewall. Sensor 1 (also called the upstream sensor) is at the outlet of the exhaust manifold before the pre-cat.

It is also possible that the intake manifold gasket is leaking air into one (or more) of the cylinders on bank 1. Usually this would happen right away after the work, but maybe the bolts worked loose.

 

I just had the same issue. I ended up taking it the dealer and they found a PVC valve that broke and was causing a leak.. They replaced it and now everything is good. I would check that first

 

if your smelling oil then that means the rear valve cover gasket needs to be torqued down to specs and basically it's leaking which will also throw the lean code....get a light and try to look back there or get it up on a lift and check it out from under u will be able to see the oil leak....make sure all hoses are plugged in including the two that go to the motor mounts....

i had had the same issue but mine wasn't leaking at all it was this a small part attached to the intake that hangs behind the engine had a leak and I replaced it and never had the problem since