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Author Topic: [2.7T] lean idle trims, rich partial trims.  (Read 13081 times)
prj
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« Reply #15 on: May 03, 2016, 11:53:13 PM »

I know the most common reply to these issues is to do a boost leak test. I've tested and tested this car to no avail.
Can you describe the exact method you used? How much pressure you used. What you blocked off and where you put pressure in?
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erykv1
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« Reply #16 on: May 07, 2016, 05:07:38 PM »

Can you describe the exact method you used? How much pressure you used. What you blocked off and where you put pressure in?



Put together a boost leak tester with a few parts.

The way I've been boost leak testing is as follows:

1) disconnect pancake valve
2) plug off pancake valve inlet on the Y pipe
3) remove intake and install the boost leak tester
4) loosen / remove oil cap
5) apply 10-15 psi, shut off the valve and listen for leaks.

it eventually bleeds down, but during the time that the system is pressurized I hear absolutely nothing.

--

I also tested the MAF harness and this is what I got:

Since it is a hitachi, I will reference the table on the right.



With the key in the ignition, I am getting the following:

- 5V when testing pins 1 and pin 3.
- 3.48V when testing pins 2 and 3.

Is this normal? I thought pin 2 was the 12V line... or does the car have to be running for it to read 12v?

« Last Edit: May 07, 2016, 05:40:27 PM by erykv1 » Logged
TijnCU
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« Reply #17 on: May 10, 2016, 09:20:01 AM »

Does the 12v power come over a relay in this engine? 12v should be reading when the engine is on ignition/not running. Also check with a real engine- and chassis ground besides the ground pin. Boost leak test should be performed on minimum the same pressure that the turbos peak at in my opinion. So if your turbos produce 20 psi, pressure test should be 20psi or more. sometimes leaks are only noticable on higher pressure.
Have you tested without maf yet?
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erykv1
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« Reply #18 on: May 18, 2016, 12:37:52 PM »

Does the 12v power come over a relay in this engine? 12v should be reading when the engine is on ignition/not running. Also check with a real engine- and chassis ground besides the ground pin. Boost leak test should be performed on minimum the same pressure that the turbos peak at in my opinion. So if your turbos produce 20 psi, pressure test should be 20psi or more. sometimes leaks are only noticable on higher pressure.
Have you tested without maf yet?

12V comes over the fuel pump relay. unless its reading voltage from some residual source.

I've had 2 other b5 s4 owners test their pins 2 & 3 and their voltages read around 2.3-2.5V, whereas mine is sitting at 3.84V. I wonder if this could be causing my high MAF readings.
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