P0171, 0174 codes :(
 

After about a 20 minute drive the CEL came on. I plug in the scanner, and I get p0171 and p0174, which I know are cly 1 and 4 running lean.

I've been googling this for a while, but I don't have any of the symptoms other people describe. My idle is smooth now. It was rough before, as it had a misfire on 5, which is why I changed the plugs and coils. The x is running smooth, accelerates better, etc.

Some say it could be an intake leak, or a vaccoum leak somewhere, but alas, I don't know where the vacuum hoses are, so I'm kind of at a loss.

Going to check the intake and clean the MAF tomorrow jic, but not sure where to look for a vacuum leak, since I've never been that car-savvy.

:dunno:

Found the culprit... must hve happened during the post-plug replacement drive.

http://i1358.photobucket.com/albums/...ps8dkarate.jpg

This one my back won'tbe able to handle... here's hoping my buddy will help out... bad idea to drive it like this? Tempted to wrap some electrical tape on it until I can go get the part tomorrow. Oh well, at least it's not an expensive part.

There is a bit of an error here. You are not lean on cylinders 1 and 4, you are lean on banks 1 and 2. Bank 1 contains cylinders 1, 2, and 3. Bank 2 contains cylinders 4, 5, and 6.

Air enters the intake via the MAF (Mass Air Flow) sensor. The volume/density of the air is measured and sent to the computer where the data is used to set the fuel delivery time -- injector on time. The goal is to achieve a mixture of 14.7:1 because this gives a balance of molecules/atoms that can will result in efficient operation of the CATs. The CATs convert the contents of the exhaust from dirty stuff into CO2, H2O, and one other compound that I cannot recall at the moment. The CAT has materials inside that have free electrons, and when these electrons combine with the 14.7:1 mixture in the exhaust, the result is clean stuff. That's what is supposed to happen.

You have a hole in the intake somewhere after the MAF. Air is entering the system that the MAF did not report to the computer, so the fuel mixture is insufficient for the amount of air -- the air fuel ratio is lean.

Follow the large duct from the air cleaner box that makes a 90-degree turn on its way to the throttle body, and you will likely find a hole in it. There are a host of other hoses in the area that break due to age and heat, and that will allow unmetered air to enter the intake system.

That'll do it.

You probably forced your gorilla-like paws into the area to retrieve an errant socket or something. This kind of thing does not break during a test drive, usually it takes a beating from the mechanic that was there last.

LOL... gorilla-like. I have very small hands. ;)

I haven't done any work on that side of the engine though. Last person in my engine before me was some techs at Jiffy Lube who did my oil change... but they wouldn't have had any reason to fiddle with the intake boot... but then given my luck with oil change places... meh.

Ah well, gonna have to pony up for this one, since my back is toast from doing the plugs, even though I took breaks and did it over a 3 hour+ period. Probably shouldn't have, given that I may need back surgery as it is :(

I have not replaced this duct/boot on my car yet. It should not be difficult to do, ignoring the physical constraints that rule your life. Assuming you could reach in and work the hose clamps, it is not a difficult job. Having said that, I know all about back pain and being sore at the end of doing pretty much anything.

The technical part of the job is not difficult, but reaching it can be. One problem is that the engine builder does his job on an engine stand so he/she can reach everything from a different angle than you and I get to use.

For BMW the failure rate is after the warranty period is over. :rofl: