Subaru Outback Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Ride of the Month Challenge!

1 - 20 of 22 Posts

·
Registered
Joined
·
106 Posts
Discussion Starter #1
Does anything look obviously wrong?


Fuel Trim Bank 1 Long Term = 7.03%

Fuel Trim Bank 1 Sensor 1 = -5.47%, -4.69%, -3.91% (fluctuated between these a couple times, or really really close)

Fuel Trim Bank 2 = 0%

Intake Manifold Pressure = 4.5psi

Mass Air Flow = 3.2-3.3

Timing 15deg @ idle

Turbo Boost & Vacuum 10.35psi (but I dont have a turbo)

Here is an O2 graph while idling, red circle at top was a real quick tap of throttle and two at bottom were longer and a little more throttle.
 

Attachments

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
Here's what I see.

Does anything look obviously wrong?


Fuel Trim Bank 1 Long Term = 7.03%

This is what the ECM is adding in fuel in addition to its base fuel map based on the data it recieves.

Fuel Trim Bank 1 Sensor 1 = -5.47%, -4.69%, -3.91% (fluctuated between these a couple times, or really really close)

This is the amount the ECM is calculating in fuel reduction to bring the AFR to a correct level. It derives this number from data received from the AF sensor.

Fuel Trim Bank 2 = 0% Ignore this

Intake Manifold Pressure = 4.5psi

This is a problem. MAP data should be about 8-9 psi. This number is telling the computer that vacuum is low, so air flow is high and its matching for higher amounts of air.

Mass Air Flow = 3.2-3.3

Your car doesn't have a MAF so the ECM calculates air flow based on BARO, MAP and IAT data.

Timing 15deg @ idle Normal

Turbo Boost & Vacuum 10.35psi (but I dont have a turbo) Software glitch with you scanner?? I think this would be the relative manifold pressure while the above MAP number is absolute.

Here is an O2 graph while idling, red circle at top was a real quick tap of throttle and two at bottom were longer and a little more throttle.

This is indicative of a failed CAT. The waveform is similar to STFT changes made by the computer in managing combustion and temperature. The CAT is not reburning the exhaust. The throttle tap was the ECM adding fuel to compensate for the throttle position. The longer throttle hold where its on the low side was the computer pulling fuel trying to adjust the AFR.

I do believe your CAT is bad. What killed it is an overly rich running engine. Your MAP sensor is sending improper data.
 

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
Be sure to replace the CAT with one that matches the programming on the ECM. Fed emissions=Fed CAT, CA emission=CA CAT. If you put a FED on a CA, you'll get a code eventually because the ECM will be looking for specific data related to CA emissions.

Check the emission sticker on the hood.

And get a Subaru MAP. I haven't had to replace one and I will assume that this will be one of those items that won't perform proper with the ECM if its aftermarket.
 

·
Registered
Joined
·
106 Posts
Discussion Starter #5
Be sure to replace the CAT with one that matches the programming on the ECM. Fed emissions=Fed CAT, CA emission=CA CAT. If you put a FED on a CA, you'll get a code eventually because the ECM will be looking for specific data related to CA emissions.

Check the emission sticker on the hood.

And get a Subaru MAP. I haven't had to replace one and I will assume that this will be one of those items that won't perform proper with the ECM if its aftermarket.
now does this vehicle have two cats? or just one?
 

·
Registered
Somebody Else's XT
Joined
·
14,437 Posts
Sounds like the MAP sensor is the bigger issue anyway. I recall that they are easy to get at, dunno how pricey they are though.
 

·
Registered
Somebody Else's XT
Joined
·
14,437 Posts
Ouch! at those prices it's worth further testing to make sure yours is truly broken. At least you can test this one with a VOM & a hand vac.
 

·
Registered
Joined
·
106 Posts
Discussion Starter #9
Ouch! at those prices it's worth further testing to make sure yours is truly broken. At least you can test this one with a VOM & a hand vac.
Yeah, I gave away my vacuum pump when we moved....I used it once when I did have it, now I need to buy another and it seems the prices have doubled since I bought mine...:28:
 

·
Registered
Somebody Else's XT
Joined
·
14,437 Posts
No fun. I got a Mity from harbor freight for $40, maybe 2 years ago? Felt expensive but turned out to be decent quality.
 

·
Registered
Joined
·
106 Posts
Discussion Starter #11
No fun. I got a Mity from harbor freight for $40, maybe 2 years ago? Felt expensive but turned out to be decent quality.
Yeah, I paid between $10-$20 for mine about 7 yrs ago...

I got rid of a bunch of stuff when we moved (cross country), now it seems I got rid of the wrong stuff, this wont be the first thing I have had to replace since moving :mad:
 

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
Keep looking for a MAP. There is a slim possibility that removing the MAP and cleaning it may help it to work again. SLIM. If its just stuck due to carbon deposit, which I don't know since there wasn't a data stream posted, its a good chance.

I sent you a PM in answer to your inquiry.

Looking at the Screwed the Pooch thread again, did the new TPS correct any of the TPS data? Or, have you installed it yet?
 

·
Registered
Joined
·
106 Posts
Discussion Starter #13
Keep looking for a MAP. There is a slim possibility that removing the MAP and cleaning it may help it to work again. SLIM. If its just stuck due to carbon deposit, which I don't know since there wasn't a data stream posted, its a good chance.

I sent you a PM in answer to your inquiry.

Looking at the Screwed the Pooch thread again, did the new TPS correct any of the TPS data? Or, have you installed it yet?
its in the mail :(

the one I cleaned did seem to get throttle reaction to improve, but performance is still sluggish and surging.

I will see about getting a vacuum pump today and checking the map.

i have to search my FSM to see if I can see what my voltage should be @ the map to start the test.
 

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
When Ed was trying to find the lines of data associated with the MAP sensor, I took photos and video of the voltage readings in relation to absolute and relative pressures as seen by the ECM. I can't find the video. I found the picture series. **** iPhone and iCloud are a pain. The video showed the gradual change in data as the pressure changed. I did it this way because none of the scan tools would combine the data with voltage readings. That's RomRaider in on the laptop screen. I had created a very slow leak in the setup. The volt meter was quicker than the software, so the reading on the meter is a tad off. Not much, its miniscule. They are a little out of order, but you get the jest.

The first pic is an edit that shows where to look in the photo for absolute and relative pressures. Absolute is the pressure on the intake. Relative is the difference between the absolute and actual air pressure surrounding the sensor using a base measure of 14.7 psi.
 

Attachments

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
The rest.

The last picture I just threw in to show the setup. Its the best I could come up with on short notice trying to move forward on the programming and easiest to transfer to Ed. Plus it was cheap. Yes that is a tire pump. From Home Depot. POS. I wouldn't want to use it for airing up a tire but it worked for this. My large portable I use for trips to Padre was with someone else.

Gotta find that video though. I don't remember how I transferred it to Ed. I think it was WhatsApp. Anyone know how to pull up message history from 6 months ago from WhatsApp? I couldn't get past 4.
 

Attachments

·
Registered
Joined
·
106 Posts
Discussion Starter #17
I saw this vid, is the starting voltage going to be 5v like the vid or different?

I was also told that unless you actually put the vehicle/map on a scope you cannot get an accurate reading of its performance, but can find if there is a leak.

what say you?

I am new to all this but having to learn since the local mechanics.....:mad:
 

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
:brainfart

Let me see if I can explain this better. Looking at the pics while I was editing the size made me think that I may not have explained it correctly. And rereading the post again. The math always goes fast in my head, so putting it down takes a bit. I never showed my work in class, just looked at it and knew. So bear with me.

And as I was leaving the shop yesterday, I had a thought to grab my small scanner when I was taking stuff out but ignored it. If I had it here at home, I could illustrate what I mean using a NA car that is MAP run with video. Seeing is believing.

The ECM calculates fuel need based on engine speed, engine temperature, ambient temperature, barometer readings, engine load, throttle position, AF sensor and MAP. It calculates a mass air flow using the engine speed, IAT and MAP data in correlation with the barometer measurement. The calculations for fuel change as any of the data from a sensor changes. Change the air temperature, and flow is recalculated. Change baro pressure and again it changes. Change the manifold pressure, guess what, new flow calculation.

The MAP sensor data is at issue. The MAP sensor voltage curve is preprogrammed in the fuel/ignition map of the ECM. It can't be changed unless you know where to find the lines of data to change the ECM's math. Since it can not change the voltage characteristic in the lines of formula, it takes it as what it sees. As in the pictures posted. The voltage on the volt meter is what the computer uses to determine the pressure on the intake and there is no changing it. WE tried. Can't find it. So if the MAP sensor is failing, it will send improper voltage back to the ECM. In this case, it would be a voltage lower than what it should be. As seen in the pics, a .1V change effects pressure calculations greatly, about .5 psi. I know its not the BARO because quick easy math says the Barometer is correct. 4.5+10.3=14.8. Close enough. That eliminates the ECM, as far as BARO is concerned.

The low MAP value suggest low pressure. Low pressure indicates the engine is pulling in more air, or a higher mass of air. The base fuel map is designed to run at a specific level of injector latency to provide the proper amount of fuel to idle the engine at the speed it holds as a target rpm. The throttle position is closed, engine temperature is leveled and the AF sensor functions but the MAP is telling the ECM that pressure is low and increase fuel to match the air flow. The AF sensor then puts its opinion in the mix and the ECM is pulling fuel to get back to stoich.

You see, the whole time the engine is actually running at a pressure equal to close to 5.5-6 psi, but the ECM is calculating the air flow at a lower pressure. The MAF reading is a calculated measurement and the measurement shown in the post is too high for a 2.5 at idle. The ECM adds fuel based on the calculated flow and adds fuel causing a rich condition. The unburned fuel lowers the AFR and the computer has to change its fuel again. This would create a fluctuating learning curve for fuel needs.

If the MAP is indeed sending the correct information, that would indicate a restriction in intake of air, a clogged air filter or PCV for instance. But that was already checked and corrected. So since we know its not a restriction, that leaves the data as incorrect which causes a rich combustion and crazy fuel trims that ultimately damaged the CAT.

I hope that makes since because I reread and edited this many times to make sure I could get the point across without taking up a lot of space with varying math calculations that would only make things worse.

Now I have a headache from over thinking how I was going to explain it. :(

On the flipside, if there is something wrong with the ECM calculation, say something that is causing a higher resistance to current flow and lowers the voltage the ECM is seeing, that would mean something wrong with the harness or the ECM itself. On the other post, "I Screwed The Pooch", I already made mention that the ECM may be bad. http://www.subaruoutback.org/forums/66-problems-maintenance/52953-i-screwed-pooch-7.html#post514979
 

·
Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
Joined
·
15,483 Posts
I saw this vid, is the starting voltage going to be 5v like the vid or different?
Map Sensor Testing - YouTube

I was also told that unless you actually put the vehicle/map on a scope you cannot get an accurate reading of its performance, but can find if there is a leak.

what say you?

I am new to all this but having to learn since the local mechanics.....:mad:
The 5 volts is a reference voltage and on the GM cars, yes. As he showed in the video, the voltage changes, lowers, with the increase in vacuum on the manifold side of the sensor.

Local mechanic or someone you know, or someone on a forum, its all the same until you know what is real. So, to put it simply, I put it in the prior post but I'll try to word it different so everyone can understand how to tell if a car has a failed MAP or a leak. And in "leak" it can be a leak within the MAP or a vacuum leak.

A leaking MAP will not hold vacuum. Done.

A vacuum leak can skew all kinds of data all over the board. When it comes to a MAP sensor's data, a vacuum leak would be indicated by a higher voltage output which means pressure is up. A vacuum leaks changes the velocity of the air flow and alters the MAP sensor feedback. The leak would also lower the MAF calculations. The AF sensor would not be stable. The rear O2 would indicate a leaner burn behind the CAT. The long term fuel trim would be high. The STFT would be high. Even with higher engine rpms, the leak is still present and will continue to skew the data.

This is why if you are going to tackle these situations that require knowing how each sensor is used and effects the performance of the engine you need to have a scan tool or software capable of seeing the data then learn how to read it. At the least you will become familiar with your car and not have to rely on the risk of bad information from someone else. Look at it this way, you only have to worry about one type of vehicle instead of several hundred and knowing will save you time and money.
 

·
Registered
Joined
·
106 Posts
Discussion Starter #20
So if you were writing a book called 'MAP For Dummies" you would be saying...

'Your MAP sensor isnt leaking its just done used up you dummy'

Or did this dummy here still not get it....

Please say I did cuz I feel like a dummy LOL
 
1 - 20 of 22 Posts
Top