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Old 01-23-2011, 01:26 AM   #1
Sylv
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Running Lean, need input

I know this has been discussed a lot and I have read pretty much every 'useful' post there is on 3 different forums, at least 10 threads

I have already replaced the oil seperator and both precat o2 sensors and the DISA; I'm pretty sure there is a vacuum leak because when flooring at high rpm, there is a sort of turbo sound (loud sucking noise);
1.) fuel trims run at 27% at idle
2.) When the engine revs down, there is 0% fuel trim and then once at idle, it goes back to 27%
3.) The vacuum sits at 21in.mg stable
4.) Unplugging the brake booster hose (going to fuel pressure regulator) has no effect on fuel trims, vacuum, or idle
5.) Opening oil cap makes idle change, you can feel a lot of suction over the oil cap hole (oil seperator replacement didn't change this diagnosis)

I unplugged the maf sensor, the fuel trims did not change what so ever, idle changed its behavior feeling a bit rough at idle; we drove it around while the maf was unplugged
1. Power felt the exact same
2. When applying the brakes while in neutral, the engine revved up to 1.2k rpm, when let off, it will go to normal 600-700 rpm

We thought that because of '2' that the brake booster would have the vacuum leak but when getting to replacing the oil seperator, we unplugged the brake booster and made a loud sucking noise, so we know it can hold vacuum and doesn't have a leak.

Which brings me here, I would assume that with the maf unplugged, I should gain performance if the maf sensor was failing, but nothing changed


Used a smoke machine to look for leaks in the vacuum and i didn't find any at all T_T

just got p2195 and p2197 codes, o2 sensors stuck lean condition..

Also, we removed the vacuum to the fuel pressure regulator expecting the fuel trim to rich out like crazy but nothing happened....i know for sure that if that was the problem, WOT high rpm would bog out and lose power, but thats not happening, i got a very smooth powerband through all revs

Your thoughts would be of great help
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Old 01-23-2011, 01:35 AM   #2
mack89
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mmmmmmm....did you check intake boots? They're usual suspects
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Old 01-23-2011, 01:37 AM   #3
Sylv
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Totally forgot that one, I replaced the lower (secondary) one; it had a crack in it, replaced it with the DISA, 1st bigger one was fine
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Old 01-23-2011, 02:28 AM   #4
mack89
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Well then..Lean issue's 100% caused by faulty intake system, and you've replaced most of the parts of it..
I would suggest you to check MAF sensor. Bad MAF sensor cannot inlet exact amount of air that engine needs, hence the lean issue.
That's all I can think of..If it's not MAF, then I really have no idea dspofjpodsajfpo
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Old 01-23-2011, 02:36 AM   #5
GRIDLOCK
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If you need a smoke test done on your intake system, shoot me a PM.
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Have an EVAP code? Replacing gas cap did not fix? Give me a holler, I can do a smoke test for ya.
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Old 01-23-2011, 05:28 AM   #6
shanneba
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Have you checked the fuel pressure at the rail? Have you tested the fuel volume from the rail? The Bentley manual has the process and specs for these tests, they are also posted in this forum.
How old is the fuel filter?
Low fuel pressure will cause a lean condition. Could be either the fuel pump or filter.

If the idle control valve is stuck open you would also get a lean condition at idle. Have you cleaned it recently?

If the secondary air pump is running continuously it will also add oxygen to the exhaust and give a lean reading. Have you checked the secondary air pump, valve and vacuum line?

What are you reading the fuel trims with? The additive fuel trim (idle) is normally listed as a ms value.
The multiplicative (part load) is normally in xx%.

Adaptation Values
In order to maintain an "ideal" air/fuel ratio, the engine control module is capable of
adapting to various environmental conditions encountered while the vehicle is in
operation (i.e. changes in altitude, humidity, ambient temperature, fuel quality, etc.).
The adaptation system can only make slight corrections and can not compensate for
large changes which may be encountered as a result of incorrect airflow or incorrect
fuel supply to the engine.
Within the areas of adjustable adaption, the engine control module modifies the
injection rate under two areas of engine operation:
1. During idle and low load mid range engine speeds (Additive Adaptation),
2. During operation under a normal to higher load when at higher engine speeds
(Multiplicative Adaptation).
These values are displayed in the "Diagnosis Requests" section of the DIS software and
is a helpful diagnostic toot that shows how the system is trying to compensate for a
less than ideal initial air/fuel ratio.
NOTE: If the adaptation value is greater than "0.0 ms" the Engine control module is trying
to en-richen the mixture. if the adaptation value is less then "0.0 ms the .Engine Control
Module is trying to lean-out the mixture.
Diagnosis Request Status Explanation
Additive mixture If the value is greater than 0.2 ms there is an unmetered air leak
adaptation (idle) or not enough fuel being supplied to the system.
The O sensor indicates a LEAN condition
The engine control module tries to RICHEN the mixture.
If the value is less than -0.2 ms there is an air restriction or too
much fuel is being supplied to the system.
The 02 sensor indicates a RICH condition
The engine control module tries to LEAN out.the mixture.
Multiplicative mixture If the value is greater than 8 % there is an unmetered air leak or
km (Part Load) not enough fuel being supplied to the system.
The 02 Sensor indicates LAN condition
The engine control module tries to RICHEN the mixture.
If the value is less than -8 % there is an air restriction or too
much fuel being supplied to the system.
The 02 sensor indicates a RICH condition
The engine control module tries to LEAN out the mixture.
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Old 01-23-2011, 05:32 PM   #7
Sylv
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Fuel Filter is about 6 months old; I cleaned the ICV already as well as the Throttle Body

So I removed the Sec Air System completely and blocked out the valve opening; now the car fluctuates between -5% to 5% fuel trims on both banks, using PCM Scan Global OBD to check this btw; during this time i created a vacuum leak and the trims went to 28%, then removed the leak and went back to +-5%; then removed the MAF and gave the same 28% Fuel Trims; so i guess it seems like the Sec Air System is down
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Old 01-23-2011, 05:51 PM   #8
jdstrickland
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The Secondary Air only pumps fresh air into the exhaust when the engine is cold. More accurately, when the CAT is cold.

The CAT needs three things, air, fuel, and heat. All of these things are in the exhaust, except when the engine is cold. The exhaust will eventually heat the CAT, but before that happens, they put in extra fresh air to compensate for the cold CAT.

The secondary air pump only runs for a couple of minutes on cold start-ups. There is a 50A fuse that operates it, and there is a salmon-colored relay in the relay box that fails, but it usually fails in a condition that powers the pump continuously, and the pump eventually burns itself out. You get a CEL when that happens, with a code that is (I think) P1421.

Lean codes come from vacuum leaks. Fuel Control or Fuel Trim errors that are not specifically rich or lean generally come from the MAF.

I think you have reached a point where you should pay to connect to the Data Link Connector with the BMW diagnostic computer. It will tell you what is wrong.
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Old 02-13-2011, 03:11 AM   #9
Sylv
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So I found something interesting I thought I should point out, I noticed that the car, after warming up, began to cool down on the temperature needle, I unlocked the OBC and went to 7.0

It seems like I average 77 Celcius, 67 was the lowest I have seen and 88 was the highest (took some time during idle), I find that to be VERY cold; I just want to confirm that this temperature is reading the ECT, and not the Coolant Temp at the radiator. Also would this have any effect on running lean at idle?

Also would like to add at WOT I hear a sort of "SSHHH" Noise at 5k+

Last edited by Sylv; 02-13-2011 at 03:16 AM.
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Old 08-28-2011, 06:03 PM   #10
danewilson77
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Sylv, did you ever resolve this issue?
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Old 08-28-2011, 10:22 PM   #11
Sylv
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Yes, I did, It turned out to be the Throttle Body Gasket, fortunately the smoke test showed me the smoke coming out of there. If you are able to do a smoke test, definitely look into that

The intake boots definitely needed to be changed though, thats for sure, good luck!
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Old 08-29-2011, 10:55 AM   #12
danewilson77
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Thanks Sylv. Guess I'm definitely looking at an intake leak then.
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Old 08-29-2011, 10:57 AM   #13
ShepsBMW
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I'm lean too, can't find it either. What a pain!
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