P0171/P0174 codes - Cold Idle/Start only

[jgold47]

I'm a little perplexed....started my car to let it warm up the other day and left it idling for 10-15 minutes (I know...sorry BMW). Came out to P0171/174 codes. Lean on banks 1 and 2. Cleared codes, have not come back after about 200 miles.

Car runs great, and has been pretty tuned up the last 10K miles or so.

New plugs
new Vanos
new DISA
New VCG
New Fuel Filter
NEw Intake Elbow
New o2 sensors
cleaned IACV

That's why I'm a bit perplexed on a lean code only after a long cold idle.

The only two other things that I could play with would be CCV (If e53's came with the cold weather CCV then I am not sure if its original or not), Or maybe the fuel pump.

Of course, it could be any one of another issue, some other gasket, etc... so maybe a smoke test is in my future.

[upallnight]

You need to do a little bit more diagnostic such as look at the short term and long term fuel trims for both banks. Since those are lean codes you need to see how much fuel is being added to compensate for the lean codes on bank one and two. I believe a 20% increase in the fuel trim will trigger a ses

[jgold47]

with the weather warming up it may be hard to replicate the conditions. I'll look into this however, and I need to get under the hood for spring maintence, so I may see something obvious. I may have mushed things around between the sunroof leaks and the wipers breaking.

Will INPA give me those fuel trim numbers.

[upallnight]

I use an App called Torque in conjunction with a a bluetooth OBD II adapter to see fuel trims.

[sunny5280]

Possibly the MAF. There's also an interesting thread on these two codes though the solution is unlikely to be your problem:

http://www.xoutpost.com/bmw-sav-foru...ighlight=P0171

[bcredliner]

It not clear to me, do the codes come back each time you let it idle for a long period of time or just that once. Do you know if the the codes were present before you let it idle? The o2 sensors your replaced were those pre cat and did you replace them with OE or OEM sensors?

Since you have driven it 200 miles and codes have not returned and there are so many potential causes I would not do anything other than periodically check to see if they do return.

Upallnight's suggestions are great but if you don't have either software, your thought of a smoke test is a good idea. If your are not familiar with INPA I think it has all long learning curve. I have a Apple app similar to Torque that I find addresses most of what I have needed and is fairly easy to use and somewhat intuitive. Sunny5280 could also be on target but you don't have a rough idle which is usually a bad MAF indication. Easy to clean the MAF just in case.

At this point, I think replacing anything is a shot in the dark.

[lhordmclain]

Double check the MAF


Adding Secondary MAF (including Pump and EGR) as a possible culprit

Tech excerpt:
The Secondary Air Injection System is monitored via the use of the pre-catalyst oxygen sensor( s). Once the air pump is active and is air injected into the system the signal at the oxygen sensor will reflect a lean condition. If the oxygen sensor signal does not change within a predefined time a fault will be set and identify the faulty bank(s). If after completing the next cold start and a fault is again present the "Service Engine Soon" light will be illuminated.

Example: Secondary Air Injection Monitoring (M54-Siemens System)
During a cold start condition air is immediately injected into the exhaust manifold and since the oxygen sensors are in open loop at this time the voltage at the pre catalyst sensor will reflect a lean condition) and will remain at this level while the air pump is in operation. Once the pump is deactivated the voltage will change to a rich condition until the system goes into closed loop operation.

Originally Posted by sunny5280

Possibly the MAF. There's also an interesting thread on these two codes though the solution is unlikely to be your problem:

http://www.xoutpost.com/bmw-sav-foru...ighlight=P0171

[sunny5280]

Originally Posted by bcredliner

It not clear to me, do the codes come back each time you let it idle for a long period of time or just that once. Do you know if the the codes were present before you let it idle? The o2 sensors your replaced were those pre cat and did you replace them with OE or OEM sensors?

Since you have driven it 200 miles and codes have not returned and there are so many potential causes I would not do anything other than periodically check to see if they do return.

Upallnight's suggestions are great but if you don't have either software, your thought of a smoke test is a good idea. If your are not familiar with INPA I think it has all long learning curve. I have a Apple app similar to Torque that I find addresses most of what I have needed and is fairly easy to use and somewhat intuitive. Sunny5280 could also be on target but you don't have a rough idle which is usually a bad MAF indication. Easy to clean the MAF just in case.

At this point, I think replacing anything is a shot in the dark.

When my X5 had a bad MAF there was no detectable operational issues with the vehicle. Only the illuminated CEL and codes are what alerted me. Lack of rough idle / stumbling does not mean the MAF is OK.

IMO cleaning the MAF is a waste of time. It won't hurt but I doubt it will solve the problem.

[bcredliner]

Originally Posted by sunny5280

When my X5 had a bad MAF there was no detectable operational issues with the vehicle. Only the illuminated CEL and codes are what alerted me. Lack of rough idle / stumbling does not mean the MAF is OK.

IMO cleaning the MAF is a waste of time. It won't hurt but I doubt it will solve the problem.

Key word in my post is "usually." You are correct there will not always be a rough idle. From my experience the cleaning only helps temporarily but I think it a worthwhile consideration in troubleshooting a fuel/air problem if only because of how quick, easy and inexpensive it is to do and does malfunction over time.

[upallnight]

Originally Posted by bcredliner

It not clear to me, do the codes come back each time you let it idle for a long period of time or just that once. Do you know if the the codes were present before you let it idle? The o2 sensors your replaced were those pre cat and did you replace them with OE or OEM sensors?

Since you have driven it 200 miles and codes have not returned and there are so many potential causes I would not do anything other than periodically check to see if they do return.

Upallnight's suggestions are great but if you don't have either software, your thought of a smoke test is a good idea. If your are not familiar with INPA I think it has all long learning curve. I have a Apple app similar to Torque that I find addresses most of what I have needed and is fairly easy to use and somewhat intuitive. Sunny5280 could also be on target but you don't have a rough idle which is usually a bad MAF indication. Easy to clean the MAF just in case.

At this point, I think replacing anything is a shot in the dark.

Torque App is free at the Google Play store, but if you like the app you should purchase. I have the Pro App on my son's tablet, but I have the free version on my Android phone.

A bluetooth OBD II adapter can be purchase on Amazon or eBay for under 20 bucks.