02 Sensor? Fuel Filter? (vida dice data included)

[carboncow]

Sure looks like it's open loop on O2 values. The sensors are not hot enough, rev up several time after full warm up. Pre-cat sensor will fluctuate 0.1-0.9V, post-cat will stay pretty steady at around 0.5V.

Understood will test out tonight.

Do you know of any other reason 02 would go into "open loop" mode and not operate...that are common?

[jimmy57]

The hose I am talking about is a vacuum line on the intake plenum that faces the head. It is on the driver's side or left end. Crankcase vent lines you removed won't be a true air leak like a hose on the intake plenum will. I don't have a car around with that intake at the moment.

[carboncow]

Thanks Jimmy, I know what you are talking about now and it worked for testing needs.

Here is some more data from testing. First I determined there is a Lamda value that tells you if the loop is open or close, so I know the system is working due to the C/L value. Correct me if I"m wrong.

Original idle value on left and value after pulled vac hose on the right:

Front 02 original value 0.99v >>> 1.10v (you suggested 1.25v)
Rear 02 original value 0.64v >>> 0.1v (you suggested 0.1v)

It took only a minute for the values to adjust to those on the right, shown above.

Then I put the hose back on and the values went to:

Front 02 0.79v (you said below 1.00v and probably 0.85v, it stayed low until I restarted the car again)
Rear 02 0.69v (while you suggested 0.75v)

So the values shifted as you suggested for proper operation but not quite the correct values you stated when pulling the hose.

Additionally, I tried the testing with the new MAF on the system and the old MAF on the system will not major difference although the values for the MAF data were:

New MAF: 9-11 kg/h
Old MAF: 11-14 kg/h

There was no noticable different in driving with the two different MAFs but the values are different.

What is a proper MAF reading and idle?

Now we get to the interesting part. I noted while looking at the graphing functionality that the REAR 02 Value would drop dramatically as the A/C compressor cycled on and off. (often below 0.1v) I dug into the options and saw I could graph the on/off off the compressor as well as the voltage. I've included a screenshot of about 7-8 minutes worth of idle. I excluded the voltage value since it made the graph messy but it was averaging about 13.8V no matter if the A/C compressor was on or off. The car makes noticeable idle issue when the A/C is engaging...none when off.

As you can see the Rear 02 Value drops during the OFF portion of the cycle. It usually did this but there were times where it would go a minute without this happening and then consistant for 3-4 minutes. The last half of the graph is when I manually turned the A/C compressor off and thus you can see a pretty steady value for the Rear 02 of about 0.64-0.66v. You can see the compressor is turned off about the 4 minute mark.

Why would the Rear 02 be fluctuation when compressor engagement, is this normal?
Do I have a questionable front or rear 02 based on this data?
Do I have another issue at work here?

I do not know when the ETM was replaced but it has been (yellow label) and the car drives well with no surging or concerns other then a soft transmissions. I would assume a bad ETM has random issues and would not cause idle concerns only when the compressor is engaging.

10-10-2011 8-10-06 PM.png (12.36 KiB) Viewed 2743 times

2001 V70 T5 160K'ish

[jimmy57]

On that car the front sensor value you see is a processed value. It is not voltage. It is Lambda. Over 1.00 is lean and below 1.00 is rich. The raw voltage is a little different car to car as it is an adapted voltage that is the product of the particular sensor, the fuel trim and a voltage signal that trims the O2 sensor delivered by ECM. The rich vs lean is determined by pos or neg current flow between signal and trim voltages. Reading the raw voltage is more or less meaningless.
Rear O2 sensor will change with engine load sometimes but slow response on front sensor will make it more sensitive and put catalyst efficiency just barely within acceptable range.
A fully warmed up engine in neutral with no A/C compressor load the MAF is usually 10-12 so the new is the more accurate. Idle program doesn't rely on MAF too much so the btter judge of MAF is fuel trim lower part load and upper part load. Of course those are not going to be good numbers if front O2 sensor is not good. My gut feeling is your front O2 sensor is weak.
Repeat the O2 test but make a controlled leak on the brake booster hose. Cut a 1/2 inch long piece of rubber hose that will fit inside the brake booster hose and then plug that with a screw or golf tee. Do the test again with fully warmed up engine and this larger vac leak. The front values could be the hose was not enough of a leak or the front sensor is bad. The re-test should make the decision easier.

[carboncow]

Jimmy,

This all makes sense to me and I should be able to test out tonight.

What is your thought on how the idle and rear 02 values being erratic with the A/C engaging? Is this a function of the posible weak front 02 sensor too? Or are we simply just talking about testing out the 02 sensors before moving on to these other symptoms?

[volvodoc]

ck ehaust manifold gaskets very closley you wont here them tick but look close from underneath and look for small black lines this will trip both codes you have because you have a air leak your car is in the right miles range for this problem this will not cause the car to stall thats a seperate prob

[jimmy57]

The a/c compressor on and off usually upsets things for an instant as throttle opens in response to a/c and closes in response to compressor off. I am curious what the long term fuel trims are for upper part load and lower part load.

[carboncow]

OK, I chased the hose from the brake booster around to the front of the intake and pulled off there. See photos for reference for others that find this post. As Jimmy said obviously a more "major" air leak. I expected the car to stall the way it was acting but it hung in there!

Note after last 02 testing CSC were reset and after two days of driving there were not errors related to long term fuel trim.

When pulling the hose:

Front 02 Value >>> 1.7-1.8 and settled in at 1.2x after several minutes
Rear 02 Value >>>> 0.10v and settled in at 0.14v after several minutes

attachment "B" shows initial values after pulling hose
attachment "C" graph shows values settle down after about two minutes

When putting hose back on:

Front 02 Value >>> 1.20
Rear 02 Value >>>> .17v

Attachment "D" shows settled in value
Attachment "E" graph shows hose getting put back on and values settling down

Note: This test was done with A/C off. I'm not sure if the sensor changes had "quick responses" as mentioned to determine how well they are doing.

How do these values look to you?

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C

C.jpg (166.48 KiB) Viewed 2463 times

D

D.jpg (231.83 KiB) Viewed 2463 times

E

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hose location.jpg (174.22 KiB) Viewed 2463 times

[jimmy57]

Front sensor response is not good. Rear went up a lot immediately on re-connect given the low amount of front sensor response.

If I were working on this it would get a front sensor

[carboncow]

Thanks Jimmy, will move forward with your recommendation and see where we land!