Enhanced Powertrain Codes

[rr080880]

I bought a 2001 740iLabout 3 months ago. It ran great and never had Service Light on... changed a lot of parts...cooling system, valve gaskets, upper timing gaskets, motor mounts, crankcase vent valve, intake gaskets, etc. Still runs great but Service Light On. Code below from a AutoEnginuity Scan.

Enhanced Powertrain

- 1C Mixture Control, Idle, Cylinder #1-4
- 1D

Mixture Control, Idle, Cylinder #5-8

I have looked incessantly for vacuum leak..multiple smoke tests, carb cleaner, and propane. Nothing detected.

Any ideas?

Thanks,

[MIKYZZ4]

Perform a fuel pressure reading,note readings at idle-2000-3000rpm,
Replace fuel filter,
repeat fuel pressure check.

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Btw,have you cleared the codes between each new scan?

[rr080880]

Thanks for the input. What are the specifications at idle - 2000 - and 3000 rpm? If these are in range, would you still need to change the fuel pressure?

[rr080880]

Sorry, I didn't see your last sentence. Yes, I clear the codes and codes reappear and service light comes on in about 5 miles. I was told to change the post-O2 sensors, not sure how that will help, but received them today and can install this weekend. Do you think that will possibly fix codes? S1 and S2 voltages and response
during live data collection on B1 and B2 appear OK...except STFT on both S2B1 and S2B2 always 99.2%, never changes.

[MIKYZZ4]

I believe 50psi is the standard for E-models.

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during live data collection on B1 and B2 appear OK...except STFT on both S2B1 and S2B2 always 99.2%, never changes.

What? 99.2% Fuel trim

[MIKYZZ4]

Pre-cat sensors effect fuel trim,
not post-cat,
they are there to monitor catalyst efficiency.

[Timm]

Use INPA to work out what is going wrong as described here:

http://www.meeknet.co.uk/E38/Diagnostics.htm

and:

[rr080880]

Update...problem fixed. Ended up taking to good Indy shop and they found air leak at VANOS gasket using their smoke tester. Brought it home, changed the gasket (straightforward 20 minute job) and no error codes. I performed two smoke tests in the last 6 weeks with a homebuilt tester. Not sure why I missed it but money well spent and car in much better shape. Thanks for your comments and help.

[MIKYZZ4]

Exactly why homebuilt smoke machines are excellent at locating massive leaks,
but useless at locating hard to find leaks,
which require the use of the $1000 professional smoke machines.