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Discussion Starter · #1 ·
I just rebuilt my b5.5 v6 02 Passat after a wreck and had to put in a cone filter as the metal was to warped for the OEM airbox. I am now getting errors P1136 and P1138 (too lean on both banks).

I am assuming that this is due to the cone filter and higher air flow into the engine. Can I ignore this error? Is there a cone filter that is close to stock inflow? OR, is there a better method to handle this?

As a side note, and I don't think this is related, but the SAI hose has not been reconnected yet -- that should not affect this, correct?

Thanks.
 

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Discussion Starter · #3 ·
I mounted it prior to the MAF sensor with some parts from advance auto.

Here is a picture, sorry it is night at the moment:
conefilter.jpg

I was assuming the MAF sensor would correct for any change in air flow, but have been reading about cone filters causing vortex instead of laminar flow which throws off the sensor. Have you heard of this?

You cant really tell in the picture, but the PCV hose in the bottom right is broken. Could this cause a vacuum leak making it run lean, or is PCV not connected to the vacuum?
 

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Are all the air path hoses intact and the joining points secure and sealed? If any air is getting sucked into the system after the MAF, it'll throw off the engine computer because it won't be accounting for that extra air.

The flow resistance of a cone filter compared to a stock filter filter isn't going to throw off the MAF. It measures how much air is passing through it weather it be behind a clogged dirty filter or no filter at all. What may effect the MAF accuracy is air turbulence caused by something up-stream of the MAF. Did the MAF have a grid (flow straightener) on the intake side that you removed?
 

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Discussion Starter · #6 ·
The grid is still there, and everything from the MAF back is stock. All new modifications are in front of the MAF. I'll double check that hose clamps are tightened down, and follow the intake back to the engine, but I don't believe that is the problem.

The MAF is from a salvaged vehicle, and I do have the original. I may try swapping them back out.
 

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The MAF is from a salvaged vehicle, and I do have the original. I may try swapping them back out.
Yea. That MAF may be bad or at least filthy/contaminated.

The open ended SAIP intake hose will not cause these problems. You may want to zip-tie a rag over the end to act as an expedient filter so nothing gets sucked into the pump.
 

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Discussion Starter · #9 ·
Thanks for the help. One more question... I've been searching around but coming up empty -- Is there a way to test the MAF?
 

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I mounted it prior to the MAF sensor with some parts from advance auto.

Here is a picture, sorry it is night at the moment:
View attachment 9147

I was assuming the MAF sensor would correct for any change in air flow, but have been reading about cone filters causing vortex instead of laminar flow which throws off the sensor. Have you heard of this?

You cant really tell in the picture, but the PCV hose in the bottom right is broken. Could this cause a vacuum leak making it run lean, or is PCV not connected to the vacuum?
That elbow mounting to the MAF housing looks sketchy. Are you sure it's completely sealed in that spot? I can't see because it isn't a close up but normally when mounting joints together you use something like this:

Vibrant 12700 Silicone Coupler 3" ID x 3" Long Black : Amazon.com : Automotive

Also I wouldn't think it would be the best idea to have a elbow right there on the MAF either. Normally with any short ram there is a good foot or more between the filter and MAF and it's a straight or 180 degree bend, or the filter is directly mounted on the MAF (bad IMO).

http://i46.photobucket.com/albums/f111/Ben_CLsales/Items SOLD/PassatIntake.jpg
 

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Thanks for the help. One more question... I've been searching around but coming up empty -- Is there a way to test the MAF?
Unplug the MAF with the car off. Turn it on and see if it runs worse.

If it runs the same, or better, bad MAF. If it runs worse, the MAF was working and now the computer is supplying a default voltage in place of the MAF.
 

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Discussion Starter · #12 ·
That elbow mounting to the MAF housing looks sketchy. Are you sure it's completely sealed in that spot? I can't see because it isn't a close up but normally when mounting joints together you use something like this:

Vibrant 12700 Silicone Coupler 3" ID x 3" Long Black : Amazon.com : Automotive

Also I wouldn't think it would be the best idea to have a elbow right there on the MAF either. Normally with any short ram there is a good foot or more between the filter and MAF and it's a straight or 180 degree bend, or the filter is directly mounted on the MAF (bad IMO).

http://i46.photobucket.com/albums/f111/Ben_CLsales/Items SOLD/PassatIntake.jpg

The elbow mounting is definitely sketchy, however I assumed that since it was in front of the MAF any leak there would be registered as flow by the sensor.
 

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The elbow mounting is definitely sketchy, however I assumed that since it was in front of the MAF any leak there would be registered as flow by the sensor.
Pre-MAF unexpected airflow is bad. Your MAF will be reading additional air coming in throwing the fuel trim off depending on how large the "leak" is. Basically you're pulling in more air then you should normally be at idle.
 

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Air leaks before the MAF are inconsequential. The worst that can happen is unfiltered air is entering the system. As long as the air goes through the MAF, it gets measured. Turbulent air entering the MAF is another thing entirely and can throw off its readings.

I'd try swapping to the original MAF to see if that helps. You can also do a flow test to see if the MAF is measuring what is expected and that the graph of the readings is smooth and consistent.

http://www.google.com/url?q=http://...YQFjAI&usg=AFQjCNFW_1uhMKQYjl057_F5Iw39N8AL2A

You'll want to find out the expected 2.8 V6 MAF readings at idle and 2000 rpm and maximum flow then compare your MAF readings to those numbers.
 

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Discussion Starter · #15 · (Edited)
Just ran a test of air flow vs RPM on VAG-COM.


in neutral:
AirFlowSensorGraph.jpg


2nd gear going up hill
AirFlowSensorGraph2.jpg

In 2nd gear up a hill I should be hitting 152g/s at 6000 rpm and am hitting 154.

I am assuming from this it is not a MAF sensor problem.

Given that I am hitting what I should on the flow through the MAF sensor, would that also indicate this is not a air leak? I am starting to wonder about the fuel lines.
 

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Guess it's time to check the vacuum lines and PCV integrity. You can check your fuel readings through VCDS.

http://www.passatworld.com/forums/6...lacing-all-vacuum-lines-2003-b5-5-v6-atq.html

17544/P1136/004406 - Fuel Trim: Bank 1 (Add): System too Lean

Possible Solutions
Check Mass Air Flow (MAF) Sensor
Check Fuel Pressure Regulator
Check Fuel Pump
Check Intake/Exhaust System for Leaks
Check Secondary Air Injection for Leaks
Check Vacuum Lines for Leaks

Special Notes
Fuel Trim Info
When this fault is stored and external vacuum leaks are not found, less obvious problems may be present:
Check Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80)
Check Brake Booster and Hoses
Check Electric Vacuum Pump ( If Applicable )
Check Crankcase Ventilation System for faulty components. When the PCV or Crankcase Ventilation System is faulty, vacuum is typically present under the oil cap and misfire faults are common.
 

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According to those results, the MAF and it's ability to measure the air with your modified filter setup looks healthy. Did you try both sensors for the 2nd gear pull? It'd be interesting to see how those numbers compare.

Check the trims to see how much the computer is correcting.
 

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Discussion Starter · #18 ·
After switching to the original MAF and doing the 2nd gear pull, I have not had the check engine light back on. I've only put about 10 miles on it today so I am going to drive around a bunch tomorrow to make sure it doesn't come back. Current trim are about 6.5% on both banks for idle and 3.5% bank 1 partial and -1.5% bank 2 partial.

If it doesn't come back I guess I picked up a bad sensor. I may throw the bad one back in again tomorrow and run the 2nd gear pull just to see what happens.
 

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Discussion Starter · #20 ·
If it was only that easy.... light came back on again. Same errors. However trim does not look too bad.

TooLean.jpg

From what I understand if the idle value is off it is usually a vacuum leak. However one of the RossTech pages I was reading said within +-10% was considered normal. The car is running great, I'm at a bit of a loss.
 
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