rn3037

17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 001 - Upper Limit Exceedd
17546 - Fuel Trim: Bank 2 (Add): System too Lean
P1138 - 001 - Upper Limit Exceeded

I've had these codes for a while, my CEL always comes back when I reset them. I also installed a new MAF, but it didn't prevent the codes from coming back.

Everyone says it looks like a vacuum leak, but I want to see what you think of my slightly low MAF readings at idle. Maybe the new MAF is faulty?

MAF READING @ IDLE: ~2.72 g/s

BLOCK 032:
Adaptation (idle) B1S1: 6.2%
Adaptation (Partial)B1S1: 12.5%
Adaptation (idle) B2S1: 6.0%
Adaptation (Partial) B2S1: 11.7%

rn3037

From Ross-Tech Wiki:
http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

It is totally normal for both the first and second fields to be something other than zero. In fact, zeros IN BOTH FIELDS indicates that either you just cleared codes (which will reset fuel trim values) or something isn't working properly. If values get too far away from zero, it will cause a DTC (fault code) and can set off the MIL (commonly referred to as the Check Engine Light, or CEL). Specifications for normal operation are usually somewhere near +/- 10%.

In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.


My second percentage is 12.5% that's what points me to the MAF being off. I am going to do a WOT run and see if the flow is down.

rn3037

Here are a few logs, I did a couple of 2nd gear runs.

rn3037

Sorry try these thinks, press the + magnifying glass on the bottom right to zoom in, you will need to press it twice.

http://s7.photobucket.com/user/Rn304...11358.jpg.html

http://s7.photobucket.com/user/Rn304...d9915.jpg.html

rn3037

I'm guessing the MAF is fine as I saw ~240-250 g/s near 6500 rpms in some logs I took today.

This looks like the biggest red flag, have to find out what is causing the lean condition at "partial" throttle.

MP4.2+6.0

Given your MAF replace and data, once you exclude vacuum and intake leak issues--especially between the MAF and the throttle body--you may want to look at O2 (lambda) sensors. It's not showing in the codes directly from what I see, but of course the sensors are where it's getting the data in the feedback loop to decide it's lean.

Since the issue seems generalized to both banks (I assume this is a 4.2 as a 2004), I'm still suspicious it's a vacuum leak. Before throwing any more $ at parts, I would unclamp everything from the MAF up to the throttle/manifold, pull it out and check it, and then reassemble carefully and tight.

rn3037

Yep my car is a 4.2 V8
Thanks for the reply! Yea I'm going to disconnect the intake pipe and look underneath. There really aren't many hoses between the MAF & TB but there are a lot of hoses going to and from the intake mani so that could be where the vacuum leak is coming from.

As far as the O2's... I haven't seen any write-ups for the D3 A8, are the pre-cat O2's a pain to get to?

Edd W

I agree, intake leaks have far less effect at WoT because the inlet depression drops to near zero, so any leak is more or less irrelevant but it will show up at idle and part throttle driving.

rn3037

I kept looking for a vacuum leak and sprayed brake cleaner everywhere on the lines and no change in idle.

Things I've done so far:
New Fuel Filter
New MAF
Passed Fuel Pressure test & idle

I did notice that I got P1111 & P1147 after testing block 107 and it always says "System Not Ok"

17544 - Fuel Trim: Bank 1 (Add)
P1136 - 001 - System too Lean - MIL ON
17546 - Fuel Trim: Bank 2 (Add)
P1138 - 001 - System too Lean - MIL ON

17519 - Oxygen (Lambda) Sensor Regulation: Bank 1
P1111 - 001 - System too Lean
17555 - Oxygen (Lambda) Regulation Bank 2
P1147 - 001 - System too Lean

* Pretty sure there is no vacuum going to these items so they shouldn't have impact on my lean codes*
17981 - Left Engine Mount Solenoid Valve (N144)
P1573 - 004 - Open Circuit
17983 - Right Engine Mount Solenoid Valve (N145)
P1575 - 001 - Short to Plus
18282 - Valve for Torque Support Mount
P1874 - 001 - Short to Plus - Intermittent

MP4.2+6.0

Have you looked at the fuel injector o rings?