Dealer smoked it, no leaks. Pulled the TB, cleaned it and Ft's improved, with no surging anymore. They didn't charge me. They told me to drive it for a couple of days and call them. Car rode home ok (1hr).
Got home with no codes. Checked readings, this is where she is at.

Idle

Bank 1
stfm 0.0
Ltft 14.8

Bank 2
stft 9 to 20
ltft 3.2


@2500 rpm

Bank 1
stft -1.6
ltft 6.3

Bank 2
stft -5 to -18
ltft 0

After some digging I also found this

stft B1-S2 0
stft B2-S2 .8

O2 Current
B1-S1 -0.02ma
B2-S1 0-.60ma

O2 voltage
B1-S2 .77v
B2S2 .90v

Maf
4.71 Idle
14.7 @2500 rpm
And I did find a hidden Po151 code (low voltage O2 sensor bank 2 upsteam)

No codes, no check engine light. But I dont have a warm feeling yet. FT's still have me concerned.

 

Hi Mark


Are you able to read any flight data, should see information about vehicle speed, temperature, MAF gm/s, etc.....


I have seen quite often O2 sensor codes, and the sensor is faulty. Are you able to watch the signal on a graph and compare to Bank 1 upstream? Otherwise you might try swapping it to Bank1, and see if Bank 1 LTFT changes.


I have seen many times where fuel injectors give problems on the 4.2 S/C, but usually it gives a code, only had one where it was hard starting after sitting over night. Cat converters have also been an issue.

 

Hi Mark,

Just to echo JB, I'm curious to know how the behavior of the Bank 2 O2 sensors compare to their equivalents in Bank 1, as I mentioned in my reply to your PM. Can you watch them in Live Data to see if one sensor behaves significantly differently than the other, or if both sensors in Bank 2 act differently than those in Bank 1?

Cheers,

Don

 

BAM!!! I knew this car wasn't running right after just a TB cleaning. Car just wasn't as smooth as usual. Slight hesitation, and not that normal "*ss pucker, put you back in the seat" acceleration.
On the way home from an hour run tonight pop went the light. When I got home I first checked voltage at the battery while at idle. Why you say? The dealer has said I've have had a charging issue with a 1 year old battery and alt.
Checked the voltage, 13.7 at idle after running for an hour with the heat and lights on.
Checked voltage with car off, 13.7. Doesn't seem to have low voltage at all. I know weak battery will create havoc, but not on just one side of the engine.

Back to the code. P0151 (bank 2 upstream O2 sensor low voltage), and no other codes. NO P0174
Could this indeed really be an O2 sensor, or is it reading whats really going on? Bank 1 readings all within specs.
The thought of cleaning the TB to correct just bank 2 doesn't seem right. Cleaning the MAF to correct just bank 2 doesn't seem right either.
The TB needed it anyway, and most likely I need to clean the MAF.
At 130000 miles I'm tempted to replace both upstream O2 sensors (cant hurt to replace bank 1 to avoid future bank 1 codes), but as many have experienced I might be really pissed if there is no change in bank 2.

 

So can you watch the Live Data on the O2 sensors to see if the voltage on the B2 upstream O2S really is low?

 

I think it'll be current sensor, not voltage. If so, just monitor the current but if it throws a code something's not right.

A bad sensor causes grief...

 

You're right, JagV8, I saw the "low voltage" wording in the DTC definition Mark is using and repeated voltage instead of current. Here's the P0151 definition from the X350 DTC Summaries Guide, which may be helpful:



Cheers,

Don

 

I hate to do it, but I'm going to throw a new O2 sensor at it. Can't hurt as 130000 miles on the original ones. $150.00 next day to my door for 2. (left and right bank)
This will rule out bad sensor one way or another. Dealer still hasn't charged me for TB cleaning....DA.
How hard is getting to the sensors without a lift? Only have ramps this week. I do have a O2 socket set. Or should I have the dealer swap them out, charge me only for the TB cleaning $100.00 (1 hr labor) and call it even.
Ordered Denso OEM

 

Mark I did mine just using ramps and I found it very easy to do. Mine were not hard to undo using an ordinary wrench.

 

Yep, same info I pasted on #19 post

 

They're easily accessible on ramps and a quick DIY. That's one reason I've been suggesting you swap them L to R. If the sensor is bad, you'll have issues in bank one after the swap.

Since it looks like you're going to buy, I recommend DIY.

 

when I checked the other day O2 current was:

B1-S1 -0.02ma
B2-S1 varying 0 to .60ma (something weird here?)

I'll read it again saturday am, and get better numbers.

 

According to the Engine Management Manual, the upstream sensor current should cycle above and below 0 amps, with expected maximum readings of +2ma to -2ma.

Cheers,

Don

 

Swapping / replacing (good idea btw) is usually not too bad BUT they can more or less weld themselves in. Then make sure you've a good socket that fits exactly as you don't want to round one off.

 

All right, here's the deal after dealer installed the bank 2 O2 sensor replacement that I supplied. No codes, no lights. Only bank 2 was changed, as only one was available in any warehouse in the country. (back ordered for a week.) Dealer still hasn't charged me a penny yet.

Bank 1 / Bank 2
stft 0.0 / 0.0
ltft 14.8 / 10.2

stft S2 0.0 / -1.6

O2 current 0.02 / 0.03
ma

EQ fuel 0.992 / 1.019
ratio?

Those are numbers we have been looking for, and I'm satisfied with 130k on the motor. No surge, no great variances. I will change bank 1 O2 sensor when it becomes available. This should bring bank 1 closer to bank 2.

What Iv'e learned:
1) Never was vac leak, but now I know. ie: cracked exhaust manifold,leaking intake manifold ect. are all tight.

2) Cleaning dirty TB made it run better (no influence on lean bank 2 codes and not listed in trouble shooting guide for that reason) But it did lead me to a lonely "O2 sensor voltage low" only code.

3) My Icarsoft cant read battery/module voltage worth a damn. My cheap voltmeter does a bang-up job.

4) An OB2 code/data reader is a must, and lifesaver. (except note #3)

5) I NOW have a full understanding of fuel trims, thanks to forum members.

6) My car had over half a dozen mechanics from this forum working on my car for the past 2 weeks. That would be about $2000.00 labor. Dealer has charged me $0.0 for the work that did not solve the issue. All of the forum members involved, charged me $0.0 for a lot of there time that could have been spent with there family.

This thread ran way to long for any of us. I can think of better things to write about. But I'm very greatfull that all of you exhausted every other solution vs throwing parts at it and hoping for the best. Time will tell.
Thanks to ALL that had a part in this journey.
Mark

PS On a funny note. The mechanic came out prior to changing the O2 sensor, to confirm with me which side (driver vs passenger). Sort of like the doctor that removes the wrong leg.
18" of snow coming tonight in Maine.

 

Keep an eye on LTFTs. They should be no more than (say) 5 at idle.

I've over 130K on roughly the same engine and LTFTs are near 1. I think yours are way too high so would watch them to see if they drop and if not go troubleshooting.

First thing is a few warm ups, then check again and then rev to about 2500 and see if they change.

 

I'll wait for a few drive cycles, then recheck ltft's. It should take a while for the ltft to relearn and adjust. In the mean time I'll clean the maf when I can get thru 18" of snow. I'll take readings prior and after. Thanks for the tip.

 

I'm really glad this appears to be working out for you Mark. You might throw some injector cleaner in the tank too before you continue to trouble shoot. That would help a clogged injector.

You've basically eliminated the fake problem that appears to be masking a potential real one.

Very good news.

 

Good plan. Sorry to hear about the snow!

 

There's nothing like the site of a clean dry Indigo Super V8 in a cleared snowy driveway. What a contrast.
Sorry, I know its off topic, just couldn't resist.