Key in, engine off, the absolute pressure reading from the MAP is wrong. I rescaled the MAP to almost, but not quite, match what the local weather station reads. Now it just about right on with to barometers that I and a neighbour has. I'm at a slightly higher elevations so my baro should read slightly less. Rescaling is a whole lot cheaper than another MAP sensor that might be off a bit too. Anyway, fuel trims changed immediately and were then averaging around zero, but only under load. Bank 1 was showing a little lean. Think I'm onto something now.

So much for smoke testing....I physically checked all around the MAP sensor and hoses leading to it. Hoses pull off way too easy and will spin around on the nipples they attach to, on the MAP, filter, and manifold. So out I went last night to a couple auto parts places to get some vacuum hose and none had any, or they just didn't sell it anymore. Weird. Friend of mine spared some that he had on a reel from 1971. It was nice thick stuff that didn't kink when bent 90*. Cut lengths that matched the OEM lines and installed those and thanked him for his 6" of hose LOL.

On the drive home I noticed the car wasn't knocking near as much. I was trying not to get excited. The Scangauge was showing that the trims for bank 1 wasn't nearly as lean anymore. Hovering between 0 and +2. Short term trim for bank 1 was following bank 2 pretty much right on over the 30 minute drive. Haven't seen this before. As soon as I got home I hooked up the laptop and checked things out with Romraider.

IAM is still 1. I'm getting even more excited. I switch over to graphing mode to do another snap-throttle test and I liked what I saw! The second peak of the MAF was now higher than the first! Another problem fixed! More to find I'm sure.

Graphs attached.

 

@cracklincrotch

I was searching the threads for "atmospheric pressure" because my ECU (KOEO) is indicating 99 kPa today, whereas the weather stations are slightly above 100 kPa. I was wondering if this might be a factor in my issues (http://www.subaruoutback.org/forums...54522-logging-ecu-data-2-5-non-turbo-what-about-iam-what-value-do-you-have.html).

When I read your thread, I was surprised by the similarities.

If I understand the information in the posts correctly, you had lean conditions which were indicated by the rear O2 sensor signals (voltage). There was also excessive knocking.

Were the lean conditions also evidenced by high positive fuel trims (which is one of the two issues I'm trying to deal with)?

The rescaling of the MAP sensor seems to have corrected much of the odd fuel trim issue in your case. Could the ~1 kPa difference I am seeing be causing the same in my 07, although not enough to trigger any codes? (Is it that sensitive?)

Incidentally, my 07 doesn't have any hoses connecting to the MAP sensor; it's mounted directly onto the intake manifold after the throttle body, so there's no vacuum lines associated, at least none I see.

 

All very interesting. I will have to check what the Barometer says here, and what RR thinks. Have you tried to see what FreeSSM thinks the pressure is? Just for comparison?

Also, regarding vac lines. Ed/XRT was telling me that my MAF, or something post MAF was leaking. Or the MAF was bad, the MAF was not Bad...I just was chasing intake leaks until I found every last one. Loose spinning hoses are not up to the intake pressures and will leak.

 

@traildogck Thanks for the ideas.

I'm using BtSsm most of the time now, but your suggestion to compare had me fire up RR. (It connects remotely to the BtSsm Bluetooth adapter, so I don't have to run the Vag-Com cable. I can run RR without having to move the laptop into the carfor KOEO readings). But, FreeSSM doesn't seem able to access the port, yet, so I haven't used it.)

Romraider reads Atm. Pressure and MAP in units (no decimals), and tonight's readings were 100 kPa and 99 kPa, respectively. BtSsm is set up to read the same two parameters in tenths, and the corresponding readings are 100.0 kPa and 99.0 kPa, respectively. (However, I'm not sure if the BtSsm readings are valid to tenths -- if the ECM only sends out data in units, the trailing zeros might just be fill.) Both show the MAP is reading one point lower than the Atm. pressure used by the ECU, and it's also one point lower than the automated weather stations in my area that are reading about 100.6 kPa. (One is not more than 2 km away.) The difference is not unlike the experience @cracklincrotch describes.

I guess the turbo input has more vacuum/intake lines than the N/A. As far as I can tell, the N/A has only the brake booster vacuum line (on the #4 cylinder runner) and the PCV lines going into the intake manifold at two points. I will check again for any sign of loose (spinning) hoses.

I wonder if cracklincrotch might have some before and after logs that can be shared here.

 

The MAP sensor on my car has a vacuum line running to it as well. I am amazed at how very few times my car throws codes. It is literally when things are unplugged.

I would expect that there is quite a bit going on in our cars before codes are thrown. That may be why...p0420 is so elusive. Many things are out of whack by then.