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01 OUTBACK VDC H6
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Discussion Starter #1
My 01 Outback VDC has run perfectly until recently. It has 107,000 miles. Misfire and stumbling on acceleration from idle. Check engine light eventually came on. Initially misfire codes for the 3 cylinders on Bank 2 (Drivers side). Eventually misfire all cylinders codes registered. No other codes. Installed new Iridium plugs (was misfiring before they were installed). No improvement. Original plugs were nice tan color. Connected Free SSM for the first time. Only figure that I can see not good is rear 02 Sensor voltage--0.9 I understand that it should not be be over 0.5 but I may be wrong. Also, I understand that high rear sensor voltage means the A/F mixture is too high suggesting an ignition problem, but again I could be wrong. Outside of misfire, no unusual engine noise.

New Cat and 02 sensors within the last 18 months.

Any thoughts on direction to proceed. Coils are expensive so I would prefer to improve the diagnosis before spending more.

All input is appreciated. Thanks.

Bob
 

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Rear O2 sensor voltage can vary between almost zero to 0.9, depending on engine operating conditions (driving, accelerating, coasting etc). Being over 0.5 V without knowing what the other parameters are saying isn't sufficient to make a judgement.

(The sensor detects oxygen in the exhaust, and compares it with the oxygen level in the atmosphere. A high voltage indicates relatively less O2 in the exhaust. In part, that's what the catalytic converter should be doing, i.e., using up any O2 that wasn't consumed during the fuel burn in the cylinders to convert remaining hydrocarbons and other combustion products to less harmless gases and water. Consequently, a high rear O2 sensor voltage isn't necessarily bad.)

A common issue with that generation is the fuel pump. Might want to check fuel pressure. See: http://www.subaruoutback.org/forums/110-gen-2-2000-2004/41182-symptoms-fuel-pump-o-ring-problem.html.
 

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01 OUTBACK VDC H6
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Discussion Starter #3
Checked fuel pressure this evening--40LB at fast idle, engine warm. In light of this, should I be pursing the o ring problem or something else.
 

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Perhaps not.

Seems to be in the ballpark.

From the FSM I have . . .

6) Measure fuel pressure while disconnecting
pressure regulator vacuum hose from intake manifold.
Fuel pressure:
Standard; 284 — 314 kPa (2.9 — 3.2
kg/cm2, 41 — 46 psi)
S2M0248

7) After connecting pressure regulator vacuum
hose, measure fuel pressure.
Fuel pressure:
Standard; 206 — 235 kPa (2.1 — 2.4
kg/cm2, 30 — 34 psi)
 

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2001 VDC/SC One of a Kind
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I doubt its the coils. Mine are at 205k miles. Plugs on the coils can be loose, but I'm discounting that because the problem was there before the plug swap. Did you replace all 3 sensors? What brand? Did you check connections? With FreeSSM, look at the voltage output of the front sensors, should be above 3V idle. What's the fuel trims showing at idle and cruising? Is the throttle body clean? What's the engine temp running? Have you replaced the thermostat yet? What condition is the battery and grounds? Do you live in an area with small varmint that tend to chew on wiring? Was there any oil in the spark plug tubes? Have you been able to check injector seals?

Bank 1 is the "hot" side of the engine. It's furthest from the thermostat and cool coolant intake. The fuel trims will be different because of the higher combustion temp (not by much). Mice like the insulation of wires. There's also the matter of chaffing due to vibration.

I ask a lot of questions, because in order to narrow down the possibilities, these things need to be verified. I don't think its fueling. Your pressure is at 40 psi, that's good.
 

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01 OUTBACK VDC H6
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Discussion Starter #6
Ummmm-that mice theory has me thinking as the car sat for a week, then the problem started. I will run a SSM and post results and address all CARDOC'S questions. Thanks.
 

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I doubt its the coils. Mine are at 205k miles. Plugs on the coils can be loose, but I'm discounting that because the problem was there before the plug swap. Did you replace all 3 sensors? YES What brand? DENSO Did you check connections? YES. With FreeSSM, look at the voltage output of the front sensors, should be above 3V idle. SEE SSM ATTACHMENT What's the fuel trims showing at idle and cruising? SEE SSM ATTACHMENT. Is the throttle body clean? I WILL HAVE TO CHECK What's the engine temp running? SEE SSM ATTACHMENT Have you replaced the thermostat yet? YES ABOUT 3 YEARS AGO WITH SUB COOLANT. What condition is the battery and grounds? GOOD Do you live in an area with small varmint that tend to chew on wiring? A POSSIBILITY. Was there any oil in the spark plug tubes? NO. Have you been able to check injector seals?NO.

I am using SSM for the first time. I assume air/fuel correction is the fuel trim. If that is the case, I go for a drive with someone else in the car to view the air/fuel correction. However, you can see the max from the attachment as I did take the car for a drive.

Once the car cools down, I will check the throttle body and look carefully for signs of varmit damage. As I said before the car sat for a week and then the trouble started.
 

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Discussion Starter #9
UPDATE CYLINDER MISFIRE----Removed engine cover and all air filter components. Evidence of mice under the intake manifold Bank 1 (passenger side). Can anyone tell me what sensors and wiring are under that side so I know what to disconnect and check the harness. Thanks.
 

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The SSM screen shot only gives a millisecond of data. The ECM is reducing fuel on bank 2, driver side, for some reason. The CAT monitor is showing lean, but this is a combined measurement from both exhaust pipes coming together after the CAT.

Here's the thing about screenshots - And this is true for any vehicle, so it doesn't matter if its a Subaru, Chevy, or crappy Daewoo. The screenshot can not show the "curve" in the data stream. The scan tool can only take in one data point at a time and has to conglomerate the data based on the speed at which the tool's software or the computer its running on can work. Even in RomRaider, the data has to be stacked and if you graph the data, you will see that the timestamps are not really at the same time. The more data points you log, the greater the curve over time. As you get accustomed to reading data, you will see more of what I'm talking about. For instance, in the fraction of time that the above data was taken, a small adjustment in throttle position after it saw the rpm on the shot could be the reason for the fuel trim change, the rear O2 sensor measurement and the AF negative value. The software pulls data in an ordered loop. Any change in the middle of the loop stacks the data, if that makes sense.

The screenshot can give you an indication of where a problem lies, but will never show the location precisely. Its like getting a P0420 code. The system is directing you to find the issue with the engine's performance and correct it before the CAT is damaged, but you have to know what to look for and the screenshot is not the place. FreeSSM is good for reading codes and looking at data on the transmission and some of the other systems. But for data logging to locate a problem, RomRaider is the best since you can save the data and look over it in multiple platforms.
 

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Discussion Starter #12
Thanks CARDOC. I will look at installing RomRaider. Do you have a suggestion for a download site? I understand several downloads are required.
 

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Discussion Starter #13
UPDATE--CYLINDER MISFIRE

Thanks to Cardoc and Eagle eye for recommending RomRaider. I have installed it and have it running and able to save the files.

I tested it today with only 4 parameters--A/F correction #1 and #2 and A/F sensor current #1 and #2. I notice that A/F sensor #1 frequently has current that is zero, and periodically A/F Sensor #2 has zero. That strike me as odd, but I don't know.

So, to do a proper analysis, can someone advise what parameters, I should record. This is a learning experience for me!

Thanks.

Bob-Subaru Forever
 

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2002 Pair: 3.0 VDC Wag & 2.5 Limited Sedan
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UPDATE--CYLINDER MISFIRE

Thanks to Cardoc and Eagle eye for recommending RomRaider. I have installed it and have it running and able to save the files.

I tested it today with only 4 parameters--A/F correction #1 and #2 and A/F sensor current #1 and #2. I notice that A/F sensor #1 frequently has current that is zero, and periodically A/F Sensor #2 has zero. That strike me as odd, but I don't know.

So, to do a proper analysis, can someone advise what parameters, I should record. This is a learning experience for me!

Thanks.

Bob-Subaru Forever


try this:

http://www.subaruoutback.org/forums/66-problems-maintenance/97977-romraider-what-data-log.html


I have not read the above thread,

but just my opinion: 1 minute logs, when the car is having the problem.

if the problem is all the time: parked idling, ...or taking off and getting up to 45mph of easy going,...

there is a setting right in rom-raider to start and stop a log via the rear defrost button the dash. (find that as a option on one of the pull downs on top)

in my case the time to record problems with the front o2 sensor was at wide open throttle when I could get a p0130 code to pop occasionally. (just had to do it on a steep hill to hold wide open for 10 seconds from a pause.

beware the readings you get will be odd at start up if you are recording, and all electrical systems self testing or dealing with the shock of the starter sequence. so maybe have the car going and then start recording.
 

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Discussion Starter #15
I have completed a test using romraider. I wanted to attach it, but apparently you cannot upload Excel files. Can someone please advise how to best upload romraider results. Thanks

Bob-subaru forever
 

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I have completed a test using romraider. I wanted to attach it, but apparently you cannot upload Excel files. Can someone please advise how to best upload romraider results. Thanks

Bob-subaru forever
you need to Zip it. before attaching.

I think the ones I made were as CSV files.
 

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Discussion Starter #18
Folks:

Attached is my Romraider test result using parameters suggested by EagleEye. It is a zipped Excel file which should pop open in Excel.

Based on that data, I would appreciated suggestions as to what is causing the misfire.

To recap---misfire at idle, stumbling on acceleration. The only codes that appear are cylinder misfire Bank 2 then Bank 1. I suspected mice on the engine, but while I saw evidence of a mouse nest, I could not find any evidence where they gnawed on the wires. o2 sensors and cat within the last 18 months. Fuel pressure 40lb. New fuel filter.

All help is appreciated. Thanks

Bob Subaur-Forever
 

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2001 VDC/SC One of a Kind
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You don't have lack of fuel, you have too much. The computer is reducing the fuel. A rich condition causes misfires in the same way a lean does, improper combustion. When you can, log it again and put in throttle position. Switch the measurement values to psi on the MAP. There is a grey box next to the parameter that allows for value choices.
 

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Discussion Starter #20
Cylinder misfire update

CARDOC, I have rerun romraider and included the throttle and MAP parameters as you suggested. I hope I got the correct ones. The test results are attached to this post as an zip files (excel spreadsheet).

Your advice is and those of others is appreciated. Thanks.

Bob- Subaru Forever
 

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