poor acceleration

[1 Lucky Texan]

well, vacuum tests seem to say the major mechanical stuff is in decent shape. No exhaust blockage either.

 

and you noted the knock sensor has been changed twice too.

 

maybe fuel trim numbers or other data ? will help if you can retrieve them from the ECU.

[alpop]

Hmm, well I guess its good news that the engine has no major problems, and as you say no blockage in the exhaust system.

 

I also noticed that if you drive like a real granny and only very slowly/gradually depress the gas pedal it does fine, acceleration keeps up with the pedal depressing, it bogs down only when you try to accelerate more briskly (normally). Its like the increase in fuel can't keep up with the increase in air unless its very gradual? Something's limiting the rate of fuel increase?

 

I ordered an Innova Equus 3040 scan tool,($60)supposed to do live data and have company support too. Sounds like the Autel wasn't supported by the company because the ones at the great price on Amazon were chinese knock-offs of the authentic(chinese)product.

 

Probably won't get to it 'till next weekend.

[alpop]

I've got data!

 

First of all I had trouble even getting (TDT)started, had to bang on the starter a few times, there has been a brief delay of 1-2 sec after turning the ignition key lately, guess I need to change out the solenoid contacts or whatever it is when you have to bang on the starter.

 

No codes until I started the vehicle, then it threw a P0507 (IAC rpm higher than expected), first one it threw on its own. Not a surprise,I knew the idle wasn't quite right and figured the IAC needs cleaning or replacement - wouldn't cause the acceleration problem.

 

Here are the numbers in the order they were displayed, first is at idle (engine warm), second is when holding at 2500-3000 RPM.

 

Fuel Syst 1: alternating between CL and OL-Drive

Fuel Syst 2: NA

Calc Load: 3.5; 7.8

ECT: 196-200, cooling fan activates at 200

STFT B1: 0 mostly until took it to 3000 RPM a few times then -7

LTFT B1: 0 then as above -2.3

MAP 7.1; 6.5

RPM: around 1000

Spark Advance: 0 initially then 15, then 50

MAF: 0 initially, then 0.5; 1.3

TPS: 0; 4.7 with smooth transition, but stayed 0.4-0.8 after goosing

O2SB1S1: 0.875 but then 0.12 to 0.68 after goosing

STFTB1S1: 0 but then -2 to -10 after goosing

O2SB1S2: 0.855 but then 0.165 to 0.76 after goosing

STFT B1S2 0, alway 0 and never changed

 

Red Flags anyone?

 

Don't know what the fuel system codes mean

 

Fuel trims: seems funny that they were mostly 0 but then after goosing varied but always negative, are't they supposed to cycle from lean to rich?

 

MAP: funny I measured 18-21 at idle, is absolute pressure different than what the gauge reads?

 

Spark advance: don't know but 50 seems like an awful lot?

 

MAF: this seems ok?

 

TPS: this seems ok

 

Don't know what these last four signify, is this the change in fuel trim (short term) in response to each of the O2 sensor readings?

[1 Lucky Texan]

not sure but what I see as fuel trims are mostly OK. single digits on an old car are not that bad. Being negative 'could' mean that there's a little misfiring /poor burning occasionally and the ECU is pulling back some fuel. (negative numbers are lean, pos. numbers are rich)

 

if you recently disconnected the battery, that may be why you're showing OL. So, the numbers you have may not be very diagnostic as the ECU is using a fixed map.

 

advance seems weird, like a bad knock sensor?

 

MAF and MAP ? dunno what's up with those, maybe someone else will have some insight.

Edited April 9, 2015 by 1 Lucky Texan

[alpop]

I think its been a month or two since I disconnected the battery. OL - what does it mean?

[1 Lucky Texan]

a month or 2 huh? OL is open loop.

 

maybe your MAF is intermittent.?

 

hope someone else chimes in with some direction for you.

[Fairtax4me]

OL- drive is kind of like a default Open loop setting used usually for wide open throttle or hard acceleration. If the fuel system switches to OL drive while at idle, that's an indicator of a sensor reading thats out of range but not enough to set a code right away.

 

MAF should not be 0 when the engine is running, but thats usually just a delay in the transfer of the initial data. Same with the TPS and ignition timing advance. Timing advance should be something like 10-12 at idle but it depends on calculated load. TPS should sit constant when the throttle is closed. Preferably right at 0.5v. ( Scanners typically show TPS as a percentage from 0-100%. This may be changeable on some scanners.)

 

MAF is something to keep an eye on though, because that may indicate the MAF sensor is sending erratic signals.

 

B1 S2 is O2 sensor bank 1 sensor 2, which in this case is the rear sensor. This sensor doesn't affect fuel trim so the STFT reading will be 0. Some scanners will also display N/A for that parameter.

 

MAP Manifold Absolute Pressure. Absolute pressure is just that, absolute pressure. Some scanners display the MAP reading in vacuum, (again, may be changeable) most just show the absolute pressure, which is any amount of pressure above perfect vacuum (0 pressure). Typically this will be very close to atmospheric pressure minus engine vacuum. ( 29 - 19= 10"Hg)

[Fairtax4me]

Fuel trims will vary. You generally want these to be around 0, but +/- 10% is typically ok.

The fuel trim calculation is percentage of fuel the computer is adding or removing from the learned base value or adaptation in order to maintain the proper AF ratio. It is NOT a rich or lean reading.

Long term trim will be a slow change. This amount is based on an average of short term trims over a period of 30 seconds to a minute. Typically increases or decreases only 2-3% at a time.

Short term trim is based on right now how much fuel is needed. This can tend to swing + to -, depending on a trend in O2 sensor readings over the course of a few seconds. If the average of O2 readings is lean the ECU will increase fuel (+ STFT). If average O2 readings are rich it will decrease fuel (- STFT).

 

O2 sensor readings tell you if the exhaust has lots of oxygen (low voltage) or very little oxygen (high voltage).

Low voltage indicates a lean AF ratio.

High voltage indicates a rich AF ratio.

 

 

The trick comes in trying to determine if one sensor is lieing and sending a false signal.

[alpop]

So that all makes sense, few things still stick out:

 

OL-drive, wouldn't stay in closed loop

 

spark adv. 50 this is what the ecu is requesting, it went up to this when I increased RPM to 3000, never went back down

 

MAF, why are people suspecting this? and what more can I do to test it

 

Would it be useful to monitor while driving? (someone else driving)

[Fairtax4me]

Go to the custom live data menu and uncheck everything except spark advance and see if it reads correctly after that.

 

MAF appears to be in the correct range. MAF flow is the primary determiner for load calculation and the load calculation is used to determine how much fuel is needed, which is why its a big deal. If the MAF signal is out of range it will create a fuel mixture problem which will affect power.

 

Check the MAF signal again (same as with the spark advance, uncheck everything else in live data menu) and just make sure the MAF signal isn't dropping too low.

Check at warm idle and at 2,500 rpm.

[alpop]

ok I get it, you get more instantaneous readings if its just looking at one thing. Will do-

[pontoontodd]

In the chance this helps your diagnosis, I've had a similar issue with my 99 Outback.

Normally this happens when it's wet.  Since I siliconed the spark plug boots in the heads it hasn't happened nearly as often.

Car will run fine until the needle on the temp gauge swings up to the middle.  Engine will stall at the next stop (manual).  Engine will immediately restart, but runs very rough.  Lots of bucking under light acceleration.  Seems to run fine with more throttle and RPM.  Shut off the engine, even for a few seconds, while coasting or stopped, and restart it and it will run fine the rest of the day.  One time I had a long drive home and the restarting trick did not work.  The engine would only run well above 1/2 throttle or near idle, which was a PITA cruising on the highway.

 

Reader's digest version - try shutting the engine off next time it runs rough, count to ten, then restart it and see if it runs better.

[subiehoe 4eva]

I have a 2000 legacy with 194k same issues only mine will do this when ever the he'll it feels like it.. Never a cel and some days it doesn't happen and others it's terrible.. I've run a scanner while the issue occurs and doesnt show anything out of the ordinary.. Been going on for about 8 months and have had 3 great mechanics get stumped.. Still no solution.. Thinking about just trading the car in. Would love to see if u figure out this monstrousity

[alpop]

 

Don't know what my chances are for beating out three great mechanics!

 

If you do a web search its amazing the number of people with this era subie that have this problem. Usually no indication if the person has got it figured out, occasionally they get it solved with knock sensor or ignition wires or something relatively simple which I've already checked. One person did solve it with a different (used) ECU, but apparently had to try a second one from an earlier year to do it.

 

I plan on doing a lot more checking with the scanner, hopefully there will be a clue. The only thing I know for sure about my problem is if you resetthe ECU (disconnect the battery for 15 minutes) it runs like a champ for twenty minutes and then starts to malfunction again, done this numerous timeslike clockwork (starts malfunctioning at the same place on the same route). I assume that for the first 20 minutes it is running in open loop on somedefault settings, and the problems start when it goes to closed loop, I will check this with my scanner.

 

 

With the car like this I can granny around this small town ok, but sure wouldn't want to hazard big city traffic with potentially little or no acceleration.

 

I've managed not to throw too much money at the problem yet, I would feel a lot worse if I had spent a lot of money and still hadn't fixed it.

 

I'm real close to dropping another ECU in there. Trouble is looks like its a lot harder to find a ECU for the 2,2, most are for the 2.5

 

I bought this in the winter for my daughter to drive in the snow, we had almost no snow, winter's now gone and its still not running right, might justsell it fixed or not.

[alpop]

New Data,

 

Things went better this time car was warmed up, stayed on closed loop the whole time and readings seemed much more instantaneous. The scanner manual says there should be a “customize settings” choice on the menu but it never showed up so I couldn’t look at any one value in isolation.

 

STFT: at idle small negatives (0 to -2), at 2500 RPM -6 to -11

 

LTFT: -5.5 pretty steady at idle, occasionally dropped down to -2 or so at 2500 RPM

 

MAP: 7.4 at idle (22.6 MP), 6.8 (23.2) at 2500 RPM

 

Spark Adv: brief flash at -64 first then very consistent 15 at idle ad 49-50 at 2500 RPM

 

MAF: very consistent 0.5 at idle and 1.2 – 1.3 at 2500 RPM – no departures

 

TPS: 0.4, 3.5 smooth transition

 

O2SB1S1 and –S2: Initially S1 cycled between 0.76 and 0.27 with S1 following 0.72 to 0.2. But when took to 2500 RPM S1 continued cycling 0.8 to 0.1but S2 stayed with small changes between 0.7 and 0.8. This situation continued for ten minutes after dropping back to idle.

 

No problems with Spark Advance, MAF, and TPS as I see it.

 

The O2 sensors are interesting, I assume they are supposed to cycle all the time in CL as observed with S1, and S2 should follow closely. But S2 did not follow (except very, very occasionally) after increasing to 2500 RPM, and then back to idle.

 

Also manifold pressure seems a little high at 22.6 to 23 (should be 17 – 21, I saw 21 with pressure gauge)?

 

Does this mean downstream O2 sensor is malfunctioning at times, or considering the slightly high MP is there some constriction in the catalytic converter causing aberrant readings in the downstream sensor?

[Fairtax4me]

Sensor 2 should not follow sensor 1.

 

First sensor is before the cat and second sensor is after the cat.

The catalyst stores oxygen in cycles. The A/F mixture is switched lean to rich and back repeatedly so the lean cycles allow the cat to store oxygen, then the oxygen is released on the rich cycles. This is done to optimize catalyst behavior (converting Oxygen and HCs into H2O and CO2) and help maintain proper cat temp.

Normally the front sensor should swing from about .2-.8v, and the rear sensor should be fairly steady around 0.45v. This can waver depending on load conditions.

High voltage at the post cat sensor indicates the sensor is reading low oxygen in the exhaust leaving the cat. Basically, it isn't storing or can't store enough oxygen during the lean swing.

Whether that's because of an AF ratio problem or because the cat is bad is harder to say.

 

Normally with a totally bad cat the front and rear sensor readings will follow each other exactly. This happens because the cat is doing absolutely nothing, the exhaust going out is the exact same as the exhaust going in. No change in oxygen content through the cat, thus no change in readings from the sensors.

On your car we know the fuel trim is being dialed back -11%. 5-10% is fine, and you're likely to see it change that much with quick changes in throttle position. But if you're holding the throttle steady, the short term trim should even back out to around 0.

[Fairtax4me]

Your MAF readings are on the high end of normal at idle, and at the low end of normal range at 2500 RPM.

You tried cleaning the MAF already right?

[alpop]

Yes I did clean the MAF, and it didn't "appear" to need cleaning.I think sometimes the MAF would go to 0.8 at idle for short periods of time.

 

In the first session with the scanner when it seemed to switch between CL and OLdrive the rear O2 sensor did seem to follow the front one (which you say is not correct). This time when it stayed on CL,the front(S1)O2 cycled as it should and the rear (S2) followed only before bringing the throttle up to 2500 RPM. Then the rear mostly stayed between 0.7 and 0.8, although yes I think once in a great while it would come down briefly to 0.4 or so and this behanior continued for 10 minutes after I brought it down to idle, then terminated observations.

 

The scanner also had a specific O2 sensor test with three categories, the first two were NA but the third was S1 value(v)0.4 and S2 value(v) 0.55.

 

So we are seeing the lean/rich swing in the front O2 sensor, shouldn't we see the swing in the STFT also?

 

Should I try a drive test with the scanner on LD and look at the MAF, or look at the O2 sensors?

 

Are we getting closer?

[alpop]

I see a procedure to test the MAF by testing the resistance of the different terminals to ground, maybe I'll do that.

 

I also see I could get a "Replacement" brand MAF sensor on Ebay for $28, maybe I should just do that.

[alpop]

So I don't know if it means anything but I tested the MAF sensor with that procedure (written for 1999 Forester with an engine that looks identical to my 2,2). It said to test each terminal of the MAF to ground, I figured terminal 3 was ground (black wire in plug and no resistance when tested against engine ground) so I put the red wire of multimeter on each of the other terminals and black wire on terminal 3, essentially testing internal resistance of each circuit.

 

Terminal expected observed

1 1.0 0

2 1.0 1.3

3 0 0

4 1 1.5 megaohm

 

I guess if the expecteds are right, then terminal 1 stands out, couldn't get a resistance despite multiple tries.

 

 

 

Looking at MAF sensors on e-bay there seem to be two types that are supposed to fit the 1999 Legacy 2.2L.

 

The one currently on the car has a receptor with room for five prongs, but only has 4 prongs, and it does not have an external wire with a diode (or whatever) on it, instead it has an etching of the wire and diode on the exterior surface (strange)

 

There is this type on E-bay and 3 of 4 sellers say it fits my car (one says no)

 

The second type on E-bay has a receptor with room for five prongs and it does have 5 prongs. It does have the external wire and diode where the etching is on the other one. All sellers say this fits my car.

 

thoughts anyone?

[alpop]

BTW we have been having warm dry weather and it has only malfunctioned in one of the last 5 drives. Previously it was doing it all the time.

[alpop]

So I bought a $43 MAF sensor on ebay, same appearance as the one in my car.  I had contacted SOA to get the correct part number for my VIN, even though this may not be valid since another 1999 2.2L engine was installed in the car to replace the original burned up engine.

 

The part from ebay was sold as a replacement part for the part# from SOA.  The part took about two weeks to get here, must have been on the slow boat from China, yes it did say Made in China on the box.

 

With the new sensor, the car would start but then only run for a few seconds before dying.  I tried resetting the computer but this did not change the behavior.  Put the old one back in and it runs as it did before.

 

Either the new part is actually not the correct part for my car, or it is completely bogus.  Looks like I could maybe get something closer to OE for around $80.

 

Unsure if I should go this route?

[lstevens76]

Subaru part number I found is: 22680AA160

 

Amazon:

74.12 for Diften 

$69.95 for Partlex

 

Both are cheaper than rockauto

[alpop]

I think that's the one for the 1999 2.5L, mine is a 2.2L engine.

 

The number SOA sent me is 22794AA000

[lstevens76]

I pulled that from the listing for a 2.2 liter on rock auto. I'm not saying it's accurate Just what they listed