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2000 Legacy stalls when clutch is depressed


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#176 2000 Legacy

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Posted 30 October 2010 - 11:03 AM

I ordered the A/F O2 Sensor early this morning and hope to have before my adult automotive class. I was wondering about taking some Live Data to see what affect the the new FPR has made, but figured I'd wait for direction since I'm not really sure about what I'm doing. I was also wondering about "adaptation" and how long it would take before things did adapt. The other concern I had was if I could do damage to the new FPR if other things still weren't correct such as the A/F O2 Sensor.

I'll also take look at the "crank" and "cam" sensors using the FSM, Fuel Injection section.

I don't mean to sound disheartened even though I am. I really appreciate all the advice and the time everyone has put in on this, as well as this forum. I also understand how hard this is for everyone not being able to see, touch or drive the car and that the car does have 200k on it. It's just that it has been a long time now, 2 plus years and about 25k miles. On the brighter side I have learned a lot, gained some confidence in working on my own vehicles and met some pretty decent people on-line and off-line.

Thanks again.
2000 Legacy

#177 hankosolder2

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Posted 30 October 2010 - 01:02 PM

A bad o2 sensor cannot damage your fuel pressure regulator, so no worries on that front.

A fresh o2 sensor does sound like a very good idea though. It's sometimes good just to replace parts so you can cross them off your list of possiblities!

#178 2000 Legacy

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Posted 31 October 2010 - 06:17 PM

Hi everyone,

I took the car out for a ride this afternoon. I plugged in the 3130 and set it to “Live Data”, “Manual Trigger”, and “Ending”. I drove the car for about 12 minutes/ 5 miles to warm it up, came to a stop sign, pushed in the clutch and the car started to stall. I pushed the Live Data button to capture the data. I pulled over and documented what was captured. I documented everything but I’ve only posted the;

Frame**STFT B1 (%)**LTFT B1 (%) **STFT B1 S2 (%) in that order, the results are as follows:

TRI**0.00**-0.7**0.00 (TRI = Trigger)
-19**-0.70**-1.5**0.00
-18**+7.80**-1.5**0.00
-17**+11.7**-1.5**0.00
-16**+10.1**-1.5**0.00
-15**-8.50**-0.7**0.00
-14**0.00**-1.5**0.00
-13**0.00**-1.5**0.00
-12**-16.4**-3.1**0.00
-11**-11.7**-1.5**0.00
-10**-25.0**-0.7**0.00
-09**-17.9**-0.7**0.00
-08**-25.0**-0.7**0.00
-07**-17.9**-1.5**0.00
-06**-25.0**-0.7**-0.7
-05**+0.70**-1.5**-0.7
-04**-11.7**-0.7**-0.7
-03**3.10**-0.7**0.00
-02**0.00**-0.7**0.00
-01**0.00**-0.7**0.00

The “STFT B1 (%)” seems to be all over the place still. Please let me know if you need any of the other data that was captured.

I took a look at the “cam” and “crank” sensors, the tips or ends of them appeared to be fine and were clean. I looked into the holes where each sensor goes into and did not see any signs of rust; I used a mirror and flashlight. None of the bolts or the support bracket for the cam sensor was loose.

The Check Engine Light came back on, only 3 codes this time (PO304, PO302 & PO301) so far. I also documented the “Freeze Frame Data” it was as follows;

Fuel Sys: CL
Calc Load: 7.4
ECT: 163
STFT B1 (%): -13.2
LTFT B1 (%): -0.7
MAP (inHg): 17.7
Eng RPM: 752
Veh Speed: 0

Please let me know if there is anything else I can do or check. Thanks.

2000 Legacy

#179 OB99W

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Posted 31 October 2010 - 11:59 PM

Okay on the cam & crank sensors and reluctor condition, and thanks for posting the fuel trims.

A quick explanation: As the engine runs, the value of fuel trim that the ECU uses to modify the injector output is the total of the STFT and the LTFT. Short-term fuel trim can vary considerably under normal conditions -- if it shows a definite trend, the ECU modifies the long-term trim, which allows the short-term to not run out of range. The problem is when the long-term value keeps climbing, and the short-term continues to cause it to move further in the same direction.

Your figures show the LTFT now averaging around -1%, while previously it was getting up to about -12%. So it seems likely that the new FPR isn't allowing the mixture to get as rich as it was before, and the ECU therefore isn't having to correct as much.

Typical failure of an A/F (O2) sensor causes it to both slow in response time and to narrow the range of the response. Often it will still see trends well enough to affect fuel trim, but not rapidly or sufficiently enough to give the ECU the instantaneous feedback it needs in order to properly adjust injector output as engine load demand changes.

I'm hopeful that a new A/F sensor will allow the ECU to have tighter control of the mixture.

#180 Olnick

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Posted 01 November 2010 - 12:48 AM

Been following this thread since it started. It's fascinating.

I feel like we're so close! YAY!!!

#181 2000 Legacy

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Posted 05 November 2010 - 05:27 AM

Hi everyone,

First I'd like to thank everyone for their time, effort and patience in trying to help me with my stalling issues along with the people that run and maintain this forum. We have fought the good fight, however I wish I could say that the "Front A/F O2 Sensor" solved the stalling issues, unfortunately it didn't. We changed it the other night in the adult automotive class that I'm taking. It came out pretty easy, we disconnected the negative battery terminal which cleared the ECU. I drove it home, about 25 miles hoping that maybe it needed to adjust itself. Let it sit overnight and through the next day and took it out last night. It stalled at every stop sign/intersection. Also the Check Engine Light came back on, I checked it and it's the same, PO304, PO302 and PO301.

The RPM's seem to be higher and it seems to idle a little better although I'm not quite sure. I think that I need to drive it for a while. I'd also like to monitor the gas mileage.

Someone had also mentioned "flashing the ECU", could this possibly do anything? Could it be that the problem has been there so long that it's inbedded in the ECU? How is flashing the ECU different than clearing the codes with the 3130 or disconnecting the negative battery? When I called one of the local Subaru dealerships to see if there were any outstanding recalls I had asked how much it cost to flash the ECU and they said it was about $40.00.

I'm tempted to just drive it as it is for now, the sad thing is that I'll be the only one that will be able to use it when I really don't need it. Oh well, this has been a great experience where I have learned so much about this car and I have met some great people on and off line. Again thanks to everyone.

2000 Legacy

#182 Fairtax4me

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Posted 05 November 2010 - 12:11 PM

Well, that's at least one more thing that you can scratch off the list, even though it didn't fix it. I've been through this type of thing before and it is discouraging when trying and trying and only being met with failure. Thus is the world of automotive repair. Sometimes you get it right first shot, others it takes 8 months of no sleep before you find the answer. :lol:

Someone had also mentioned "flashing the ECU", could this possibly do anything? Could it be that the problem has been there so long that it's inbedded in the ECU? How is flashing the ECU different than clearing the codes with the 3130 or disconnecting the negative battery?


Not quite. A re-flash of the ECU will re-program the base parameters for all of the control systems. These are the starting parameters that the ECU defaults to when you clear the memory by disconnecting the battery.
There are also many algorithms and programs running in the ECU that a basic scanner can not change. These can deal with anything from oil level monitoring (mostly in newer vehicles) to which point in the rpm range the ignition control system advances or retards timing to correct or prevent certain conditions, or how long the evap purge control solenoid stays open when you take your foot off the throttle. A change of mere milliseconds can make a difference in what the ECU "sees" through the various sensors on the engine.

When you erase codes or clear the ECU by disconnecting the battery, you just erase the memory of what has happened and what the ECU has learned during the last few drive cycles. A re-flash erases and replaces the core settings and programming that allow it to run in the first place.

#183 OB99W

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Posted 05 November 2010 - 05:57 PM

I'm sorry that the A/F sensor didn't resolve the stalling problem. I'm willing, if you are, to try a bit more diagnosis.

We haven't looked at the live data since the FPR and A/F sensor were replaced. There may have been changes that would be revealing. If you feel like it:
1) Warm the engine to normal operating temperature
2) Use the 3130 and note all the live data parameter readings at idle
3) Watch them for a while, and if any change much, note that as well
4) Bring RPM up to 1500, and again note all live data parameters

I'm interested in seeing all the data, although in particular I'm wondering where the "Calc Load %" and "Spark Adv" are at now. The spec range for engine load at idle is 1.6-2.9%, but previous readings indicated around 5% (about double the norm). Also, the ignition advance was retarded from normal and varying before. In addition, although lessened after the FPR change, the LTFT was still heading a bit negative, meaning the ECU was seeing the mixture as somewhat rich.

You may wonder why I'm concentrating on those three parameters. The reason is because a vacuum leak will cause the MAP to be high, which in turn causes the ECU to calculate a higher load, resulting in ignition timing being retarded and mixture being enriched! I know that you checked and didn't find a vacuum leak, but perhaps there's one that escaped detection.

So, that's why it would be good to know what the live data shows now.

#184 OB99W

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Posted 05 November 2010 - 06:36 PM

Not to distract from my post above, but did you check into what Gloyale mentioned in the last paragraph of post #35 in this thread? As he mentions, there can be crosstalk between the ignition cables and injector wiring if they're too close to each other. In fact, if the ignition cables have been replaced, it's important that the factory corrugated wire loom is in place -- unfortunately, sometimes it doesn't wind up on the replacement cables. See if your plug wires look like the attachment.

Attached Files



#185 2000 Legacy

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Posted 05 November 2010 - 07:56 PM

Thanks again for reflashing information and for not giving up on me yet even though I had it in my mind that I would at this point. I'll continue but may not be able to get to the additional diagnosis until late Sunday or early in the week. I'll also check the plug wires. Thanks.

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#186 OB99W

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Posted 05 November 2010 - 10:12 PM

Personally, I only "give up" when the other person wants to, they continually ignore my suggestions, I run out of ideas, or we resolve the problem. Naturally, I prefer the last of those. :)

#187 2000 Legacy

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Posted 09 November 2010 - 05:14 AM

Good morning everyone,

Last night I started up the Legacy and let it warm for 10 minutes, I then documented all of the “Live Data” at idle with the 3130 every 10 minutes. I did this four (4) times, the documented results below are in that order starting at 5:30 PM and finishing at 6:00 PM, they are as follows:

Fuel Sys 1: CL, CL, CL & CL.
Calc Load (%): 5.4, 4.7, 4.3, 4.7 but then dropped to 4.3, then 3.9.
ECT (Degrees F): 190, 190, 186 & 195.
STFT B1(%): -18.7, -21.0, -17.9 & -18.7.
LTFT B1 (%): -1.5, -1.5, -1.5 & -1.5.
MAP )inHg): 14.7, 12.6, 12.1 & 11.5.
Eng RPM: 667, 673, 653 & 676.
Veh Speed: 0, 0, 0 & 0.
Spark Adv: 4, 5, 11 & 6. Note it did go as high as 12 but then drop as low as 4.
IAT (degrees F): 51, 64, 86 & 109.
MAF (1 lb./min): 0.682, 0.615, 0.575 & 0.511.
TPS (%): 0,0, 0 & 0.
O2S B1 S2 (V): 0.820, 0.850, 0.875 & 0.845.
STFT B1 S2 (%): 0,0, 0 & 0.
OBDSup: OBD2, OBD2, OBD2 & OBD2.
O2S B1 S1 (V): 3.845, 3.796, 3.767 & 3.679.
EQ Ratio 11: 0.973, 1.030, 0.999 & 1.011.

I also documented the “Live Data” at 1500 RPM’s at 5:52 PM which was in-between the 3rd and 4th time I documented Live Data at idle. Those results were as follows:

Fuel Sys 1: CL.
Calc Load (%): 7.0.
ECT (Degrees F): 201.
STFT B1(%): -20.3 but also rose to as high as 1.5.
LTFT B1 (%): -3.1.
MAP )inHg): 8.8.
Eng RPM: 1500 about.
Veh Speed: 0.
Spark Adv: 28.
IAT (degrees F): 93.
MAF (1 lb./min): 0.939.
TPS (%): 2.3
O2S B1 S2 (V): 0.860.
STFT B1 S2 (%): 0.
OBDSup: OBD2.
O2S B1 S1 (V): 3.277 or 3.277 (can’t read my own writing).
EQ Ratio 11: 0.994.

I checked the spark plug wires, the factory corrugated wire loom was on all four wires and the wires were all clipped in their own little brackets. The wires appeared to be in accordance with the picture however on the passenger side the forward most wire wasn’t as straight as shown in the picture, it seem to loop or roll close to the aft wire. But like I said the wire loom was in place and the wires were clipped into the brackets. I did try and twist the spark plug wire at the plug and it seem to roll away. I guess I could unplug it to reposition it however it was dark and cold so I didn’t.

Hope this all helps. Thanks again to everyone who is reading and posting advice.


2000 Legacy.

#188 OB99W

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Posted 10 November 2010 - 07:17 PM

Last night I started up the Legacy and let it warm for 10 minutes, I then documented all of the “Live Data” [...]

Thanks for posting that. I've been very busy, and may not be able to respond to what I see in the data for a few days. However, at least one of the PIDs interested me enough to call tech support at Innova. When I post next, I'll explain and have some comments and further suggestions.

Until then, would you please run a live data check once more? Fully warm the engine (ECT = 190 or so). Bring the engine speed up to 2500 rpm, and hold it there for a full two minutes. With it still at 2500 RPM, note O2S B1 S2 (V) (rear oxygen sensor voltage). If it's fluctuating, make note of the range of values. If steady, note that reading. Thanks.

#189 2000 Legacy

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Posted 11 November 2010 - 04:56 PM

Hi,
You’re welcome for the last posting, thank you for your time and research especially for calling the Innova tech support. As far as being busy the next few days I understand completely. Take your time.

First I plugged in the 3130 and then warmed up the car this afternoon, I let it idle for about 20 minutes and then drove it around the block, about 2 miles. I then brought the RPM’s up to 2500 and held it there for 2 minutes. After the 2 minutes I held it at about 2500 RPM’s and documented the Live Data, it was as follows:

Fuel Sys 1: CL
Calc Load (%): 12.9
ECT (degrees F): 195
STFT B1 (%): 1.5
LTFT B1 (%): -11.7
MAP (inHG): 8.5
Eng RPM: 2531
Veh Speed: 0
Spark Adv: 33
IAT (degrees F): 100
MAF (1 lb./min): 1.490
TPS: 5.8
O2S B1 S2 (V): 0.705
STFT B1 S2 (%): 0
OBDSup: OBD2
O2S B1 S1 (V): 3.762
EQ Ratio: 0.997

After that I went back to the “O2S B1 S2 (V)” and held the car at about 2500 RPM’s for about 4 minutes and documented the fluctuating range values, the range was 0.525 to about 0.710. I’m not sure how accurate that was due to the fact that it was hard to keep the car at exactly 2500 RPM’s for that period of time.

I then let car go back to idle and documented the Live Data again, it was as follows:

Fuel Sys 1: CL
Calc Load (%): 3.5
ECT (degrees F): 197
STFT B1 (%): -16.4
LTFT B1 (%): -3.1
MAP (inHG): 10.9
Eng RPM: 688
Veh Speed: 0
Spark Adv: 8
IAT (degrees F): 125
MAF (1 lb./min): 0.502
TPS: 0
O2S B1 S2 (V): 0.840
STFT B1 S2 (%): 0
OBDSup: OBD2
O2S B1 S1 (V): 3.821
EQ Ratio: 0.976

Hope this is useful, I know that you didn’t request all of the above but figured it couldn’t hurt. Please let me know your thoughts and what you think we should do next. Thanks.

2000 Legacy

#190 samneric

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Posted 12 November 2010 - 09:14 AM

I've been reading and am fascianted by this thread.

I think its a great learning opportunity for everyone here - I've learn't a bunch already and am keen to learn more.

That said, I would like ya'lls opinion on this neat looking utility..... I'm a great believer in utilising the computer in my possesion rather than buying individual computers for individual tasks so when someone makes an interface to either usb/serial I get excited :)

Anyways, let me know if anyone has ever used this or there is another, better option...

http://www.nology.com/laptopdyno.html

I would figure that looking at real-time graphs of the sensors would help out here....

Steve

#191 Fairtax4me

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Posted 12 November 2010 - 05:01 PM

However, at least one of the PIDs interested me enough to call tech support at Innova. When I post next, I'll explain and have some comments and further suggestions.

Well!?!?!?! Don't leave us hanging!!! The suspense is killing me! :lol:

That said, I would like ya'lls opinion on this neat looking utility..... I'm a great believer in utilising the computer in my possesion rather than buying individual computers for individual tasks so when someone makes an interface to either usb/serial I get excited

Anyways, let me know if anyone has ever used this or there is another, better option...

There was a gadget that was really popular a few years ago (might still be I don't know) that mounted inside the car, had a little screen and some buttons. You put in a bunch of numbers (weight, gear ratios, etc) and it would time you for 0-60 or 0-100 and tell you all the same stuff that software does. Can't remember for the life of me what it was called though.
Might try starting a new thread about it to get some other opinions from people who might not have the patience for a thread of this length. :lol: There are actually quite a few programs like this floating around that deal specifically with subaru. I used to have some bookmarked, lost them the last time my computer crashed. :-\

#192 samneric

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Posted 12 November 2010 - 07:01 PM

I used to have some bookmarked, lost them the last time my computer crashed. :-\


Bet you won't do that again...

Backup Backup Backup!!!

And never forget....

JESUS SAVES!!!!! :lol:

Steve

#193 OB99W

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Posted 16 November 2010 - 11:39 PM

Well!?!?!?! Don't leave us hanging!!! The suspense is killing me! :lol:

Sorry, time constraints. Hopefully everyone is still alive. :)

There are numerous parameters associated with OBD-II data, such as O2 sensor voltage, long term fuel trim, etc. These parameters are standardized, and have been assigned identification numbers. Since a computer (ECU) is involved, the Parameter Identification (PID) numbers are in hexadecimal, a number base convenient for programming. (See http://en.wikipedia.org/wiki/Hexadecimal if you'd like more on "hex".)

As I mentioned previously, at least one of the PIDs in the live data that Legacy 2000 was reporting had me wondering what was going on. For example, there was MAF data, even though there's no MAF sensor on a 2000 Legacy. So, I decided to speak to tech support at Innova (the manufacturer of the Equus 3130 scan tool). I explained about the phantom MAF reading (and other things), and was told that the scan tool just communicates with the ECU using PID numbers (and apparently then converts those into the equivalent "LTFT", "MAP", etc., displaying them that way for easier reading by average humans :) ).

With that in mind, I looked at what was reported by 2000 Legacy in post #187 (I added the matching PID numbers):
03 Fuel Sys 1: CL, CL, CL & CL.
04 Calc Load (%): 5.4, 4.7, 4.3, 4.7 but then dropped to 4.3, then 3.9.
05 ECT (Degrees F): 190, 190, 186 & 195.
06 STFT B1(%): -18.7, -21.0, -17.9 & -18.7.
07 LTFT B1 (%): -1.5, -1.5, -1.5 & -1.5.
0B MAP )inHg): 14.7, 12.6, 12.1 & 11.5.
0C Eng RPM: 667, 673, 653 & 676.
0D Veh Speed: 0, 0, 0 & 0.
0E Spark Adv: 4, 5, 11 & 6. Note it did go as high as 12 but then drop as
low
as 4.
0F IAT (degrees F): 51, 64, 86 & 109.
10 MAF (1 lb./min): 0.682, 0.615, 0.575 & 0.511.
11 TPS (%): 0,0, 0 & 0.
15 O2S B1 S2 (V): 0.820, 0.850, 0.875 & 0.845.
15 STFT B1 S2 (%): 0,0, 0 & 0.
1C OBDSup: OBD2, OBD2, OBD2 & OBD2.
14 O2S B1 S1 (V): 3.845, 3.796, 3.767 & 3.679.
24 EQ Ratio 11: 0.973, 1.030, 0.999 & 1.011.

The same PIDs, from the CanOBD2 (Innova) Website:
03 - Fuel System Status
04 - Calculated Load Value
05 - Engine Coolant Temperature
06 - STFT Bank 1, Bank 3
07 - LTFT Bank 1, Bank 3
0B - Intake Manifold Absolute Pressure
0C - Engine RPM
0D - Vehicle Speed Sensor
0E - Ignition Timing Advance for #1 Cylinder
0F - Intake Air Temperature
10 - Air Flow Rate from Mass Airflow Sensor (MAF)
11 - Absolute Throttle Position
14 - Oxygen Sensor 1 Bank 1
15 - Oxygen Sensor 2 Bank 1
1C - OBD2 Support Requirements
24 - Oxygen Sensor Equivalence Ratio/Voltage (bank 1, sensor 1)

So, why is there MAF data? From the 2000 Legacy FSM:
03 Fuel system control status
04 Calculated engine load value
05 Engine coolant temperature
06 Short term fuel trim
07 Long term fuel trim
0B Intake manifold absolute pressure
0C Engine revolution
0D Vehicle speed
0E Ignition timing advance
10 Air flow rate from pressure sensor
11 Throttle valve opening angle
14 Oxygen sensor output voltage and short term fuel trim associated with
oxygen sensor - bank 1
15 Oxygen sensor output voltage and short term fuel trim associated with
oxygen sensor - bank 2
1C On-board diagnosis system

Ahhh, PID#10, as Subaru defines it for the 2000 Legacy, is not "Air Flow Rate from Mass Airflow Sensor (MAF)", but "Air flow rate from pressure sensor". The 2000 Legacy uses a "speed density" system -- the ECU calculates air flow rate using engine speed (RPM), manifold absolute pressure (MAP) and intake air temperature (IAT), so what it's reporting as PID#10 is calculated by the ECU using that data, not read from a MAF sensor.

In looking over the FSM PID list, I also noticed some errors and omissions:
0F - Intake air temperature (IAT) - missing from list, but reported in data
14 - doesn't mention this is for sensor 1 (front A/F sensor)
15 - should be bank 1, sensor 2 (rear O2 sensor)(*not* bank 2)
24 - Equivalence ratio bank 1, sensor 1 (EQ Ratio 11) - missing from list, but reported in data

In addition, I spoke to Innova about the STFT B1 S2 (%) consistently being 0%. Apparently since PID#15 includes both the rear O2 sensor voltage and its effect on STFT, the 3130 reads and reports the voltage and the STFT info as well. If it displays 0%, that means the ECU doesn't use the rear O2 reading at all to affect STFT (but only to determine that the cat is doing its job).

So, that clears up some of the mysteries of the live data readings. It's late and I'm tired, so I'll post again tomorrow with where I think this is all leading.

#194 Fairtax4me

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Posted 17 November 2010 - 12:29 AM

Not dead yet! :banana:
Interesting stuff. It hadn't crossed my mind that the 2000 model does NOT have a MAF sensor.
So it's possible for the ECUs air density calculation to be wrong if either the MAP or IAT sensor is out of whack. Or even if both are working properly a fault in the algorithm that determines the density might affect the changes the ECU makes to the fuel trim?

If it displays 0%, that means the ECU doesn't use the rear O2 reading at all to affect STFT (but only to determine that the cat is doing its job).

I see questions concerning the role of the rear O2 sensor all the time and that is the exact answer.

#195 OB99W

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Posted 17 November 2010 - 01:51 PM

So it's possible for the ECUs air density calculation to be wrong if either the MAP or IAT sensor is out of whack. Or even if both are working properly a fault in the algorithm that determines the density might affect the changes the ECU makes to the fuel trim?

Yes, those things could all potentially result in an incorrect determination that could cause the ECU to improperly set fuel trim.

However, in the case at hand we've verified that both the MAP and IAT sensors appear to be working and producing data that's within tolerance, an FPR that regulated the fuel pressure too high has been replaced, and the front A/F sensor has been changed. That would leave the ECU's determination to be at fault, if we assumed it was the only remaining possibility, but ECU failures are rare.


I see questions concerning the role of the rear O2 sensor all the time and that is the exact answer.

It's correct for cars like the 2000 Legacy that don't use that sensor for anything more, although others do. And just because it's purpose might be primarily to determine if the cat is functioning well doesn't mean we can't use the voltage reading for diagnostic purposes.

If the rear O2 sensor voltage remains somewhat above 0.45 volts, and doesn't fluctuate much, that's usually a good sign. All other things performing correctly, it would indicate that there wasn't excessive oxygen in the exhaust after the cat was done with it, so that likely CO was being oxidized to CO2, etc. But a rich mixture would also be lacking oxygen, and could drive the sensor above 0.45 volts as well.

Notice that the rear O2 sensor has been at about 0.85 volts at idle, and that with the MAP and IAT looking good and the FPR and A/F sensor replaced, the ECU is still trying to cut fuel (negative trims). From post #189, though, at 2500 RPM "O2S B1 S2 (V)" drops to "0.525 to about 0.710" volts, and the STFT goes positive (thanks for the additional data, 2000 Legacy). We've noted all along that the engine runs better at higher RPM, both in terms of drivability and what the live data shows.

Many things have been ruled out either due to tests or replacement, and yet low speed operation is still not quite right. Since idle and slightly higher speeds are mainly controlled by IAC, parts associated with it should probably be looked at again. The system on the 2000 Legacy uses air-assisted injectors. With an auto trans, there's an air-assist solenoid to control things, but the manual trans version is different. At idle, air via the IACV is split into that needed for intake (bypassing the closed throttle plate) and the remainder, which is used for injector assistance. Since the IACV itself was replaced by the dealer without improving the symptoms, it's possible that there's a partial blockage in a throttle body passage (which I mentioned in post #94, suggesting looking at the P0506 procedure). Previous cleaning might not have been able to resolve this.

It could be useful to find out what duty cycle the ECU is applying to the IACV. Unfortunately, that's not an OBD-II PID that the Legacy provides. It can either be read with a Select Monitor, or using an oscilloscope (which is what I'd do).

If anyone has an idea about something we haven't already considered, please speak up -- I'm running out of suggestions.

#196 samneric

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Posted 17 November 2010 - 02:19 PM

If anyone has an idea about something we haven't already considered, please speak up -- I'm running out of suggestions.


The two times I've suffered from similar symptoms (stalling on idle) over my life of driving fuel injected cars, the cause has been as follows:

A Vauxhall Astra GTE - A split vacuum hose.

A Toyota Celica - Gummed up IAC Valve.

With all the troubleshooting of the electronic management system so far prooving unconclusive, I'm guessing that the problem will end up being something mechanical - vacumm leak, blockage, dirt etc etc.

Just my 10c

Steve

#197 hankosolder2

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Posted 17 November 2010 - 06:51 PM

Many years ago, when I was working at a gas station we got a Ford Ranger (2.3 4 cyl) in that would stall whenever it was put in Drive. (This was pre OBD anything.) It had the speed/density algorythm with a MAP sensor type EFI. It was running super rich, especially at idle. Long story short, the mechs discovered that it had wiped out a cam lobe-which was causing it to not pull enough vaccuum which confused both the MAP sensor and the fuel pressure regulator.

Is the performance of the car normal above idle? I know subarus aren't prone to wiping cam lobes like the 'Pinto' engine, but any car with 200K miles can have various mechanical wear issues. I think a partially worn cam lobe could possibly still give decent compression and slightly low vacuum readings at idle?

Finally, was the fuel pressure verified to be normal after the FPR was replaced? I've lost track in this lengthy thread.

Depending on how long the OP wishes to keep the car, I'd be tempted to start trying a kludge to get the idle mixture in the ballpark- you could add a either a padding resistor in series with the ground lead of the MAP sensor or a voltage divider on its output to shift the fuel curve around a bit. (Don't know if the MAP puts out more voltage at higher vacuum or vice versa- anyway, you want to fake it in the "more vacuum" direction.) An adjustable fuel pressure regulator would be another kludge. These are strictly last resort "ghetto" suggestions, but if it's a matter of squeaking another year out of the car 'till you can afford something else, it's a thought, especially if the root cause is determined to be engine wear causing low vacuum.

Nathan

#198 OB99W

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Posted 18 November 2010 - 10:37 AM

[...]Is the performance of the car normal above idle? I know subarus aren't prone to wiping cam lobes like the 'Pinto' engine, but any car with 200K miles can have various mechanical wear issues. I think a partially worn cam lobe could possibly still give decent compression and slightly low vacuum readings at idle?

The engine apparently seems "happier" above idle, although perhaps not "ideal". Certainly wear might have changed valve clearances by now, although it's hard to say to what degree without checking. At it's current mileage, the engine probably should have had two valve adjustments. I don't know if it's had any.


Finally, was the fuel pressure verified to be normal after the FPR was replaced? I've lost track in this lengthy thread.

I don't believe the pressure was rechecked after the FPR replacement. I did suggest to 2000 Legacy that the vacuum at the FPR be checked, and he also reported that the fuel return line seemed clear to the tank (tested by air passage). However, verifying that the new FPR has brought the pressure within specs is a reasonable thing to do.

#199 hankosolder2

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Posted 18 November 2010 - 05:13 PM

I don't believe the pressure was rechecked after the FPR replacement. I did suggest to 2000 Legacy that the vacuum at the FPR be checked, and he also reported that the fuel return line seemed clear to the tank (tested by air passage). However, verifying that the new FPR has brought the pressure within specs is a reasonable thing to do.


Yes, just as an example, suppose the return line is almost fully crushed or a hose has an internal blockage- it could cause high fuel pressure, especially at idle and still be able to pass air bubbles to the tank. As the return fuel volume decreases at higher speeds and throttle openings (i.e when more fuel is used by the engine, less goes through the return line) things would be closer to normal. I'd sure want to know that the fuel pressure was normal before doing anything else.

#200 2000 Legacy

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Posted 20 November 2010 - 05:00 AM

Hi everyone,

Thanks for all your effort and time on this problem. I’m sorry that I haven’t responded sooner, I’ve been busy like everyone else and I was and am a little overwhelmed by some of the responses. You guys are way over my head; I wish I had some of your analytical thought. Anyways, thank you.

The dealer supposedly replaced the IACV as well as the fuel injectors; they didn’t work so I had them put my old ones back. I’ll have to relook at the procedure for a P0506 to see what that entails.

As for checking the “duty cycle” the ECU is applying to the IACV, I’ll have to look around to see if someone has an oscilloscope, not that I’d know what to do with it, but I’ll cross that bridge once I get ahold of a scope.

There are a few things I need to look up that I didn’t understand; like cam lobe, algorithm and kludge.

I’ll also look at rechecking the “fuel pressure” with the new FPR as well as the vacuum. Is there any other way of checking the return line other than what I did (blowing air at the FPR and listening at the fill pipe for the gas tank)? Also I haven’t checked the gas mileage with the new FPR and O2 Sensor. I would think that would tell something with regard to fuel.

Another thing mentioned in Post # 198 was “valve adjustments”, I’m not aware that the car has had any and like I mentioned in the beginning is that we bought this car brand new in 2000. I have to admit I’m not familiar with this and do not know what is involved with valve adjustments.

Again everyone, thank you.
2000 Legacy.




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