I am getting my 2004 with 87,000 miles ready for a smog test next month and trying to complete the Comprehensive Component Monitor test. Everything else is set. While I am in the process of putting some miles on to complete the drive cycle I have been watching my OBDII code reader a lot. My question is my fuel trim readings for Bank 1 seem to be somewhat lean while Bank 2 is doing fine. I do not have any codes pending or set (P1000 only). Although with the Comprehensive Comp. Mon. not complete maybe it will not show any? My closed loop readings when cold are fine. However, after it is hot at an idle I get ST FTRM1(%) -0.8, LT FTRM1(%) 3.1 ST FTRM2(%) -2.3, LT FTRM2(%) 0.8 ↑.

Yesterday I had her on the highway to complete the Evap. Monitor and when hot at idle had readings of ST FTRM1(%) 1.6 ↑, LT FTRM1(%) 2.3, ST FTRM2(%) 0.8, LT FTRM2(%) 0.8. The LT Trim for Bank 2 is very consistent at around 0.8 and Bank 1 is always around 2.? - 3.?.

I have recently replaced the battery (Exide), spark plugs (NGK 5464 supposed to be better than the 7866 but do not last as long), 2 coils (Airtex/Wells 5C1420 on cylinders #3 and #8) due to damage while removing them to change the spark plugs, replaced the fuel filter (Wix) and cleaned the MAF sensor (LB/M .57 - .66). The spark plugs on Bank 1 seemed to be a little “wet” but overall I believe not too bad. The tubes for the spark plugs are fine (no oil) and cannot find any vacuum leak. Regardless I replaced all of the o-rings I could find while doing the “tune-up".

Should I be concerned with these readings? I do not have and roughness and do have plenty of power. I do not anticipate any problems passing my smog test but wonder why Bank 1 is so much different from Bank 2.

 

Both LTFTs are below 5 so I'd not worry.

The attached TSB may be why you're having trouble

 

Whenever I see a big difference between banks (not in this case), I suspect O2 sensor problems. I spent forever chasing an intermittent misfire across all cylinders on one bank of a Porsche Cayenne Turbo. Turns out I had a bad 02 sensor. It doesn't sound like this is a problem in your case but once you get over 100K miles any bank dependent problems could be a sign its time to replace a sensor

Steve

 

It's easy enough to swap banks and see if it follows the sensor, but realistically, by the time 100k has passed, it's time for a new set of all 4 sensors. They're not that expensive and are a regular maintenance item.

 

Thank you for the TSB JagV8, I had not came across that one yet. There are a lot of issues regarding the 04-05 models and the California smog rules. I will try and do that drive cycle next. I got sidetracked today by picking up a set of 17" wheels to trade off my 18"'s. My original rims have bad curb rash and these are new looking.

I do plan on replacing the sensors as I agree the high mileage and also age require some items to be replaced at some point as part of regular maintenance. Thus at 14 years and 87,000 miles they have served their purpose and probably out lived their life expectancy. Currently I believe my O2 readings are decent (O2S12 (V) 0.090, O2S22 (V) 0.095, EQ RATIO11 0.0943, 02S11 (mA) - 0.051, EQ RATIO21 0.0966↓, 02S11 (mA) 0.055) so I think I will get them and have them on hand. I just observed the condition of some of the rear suspension bushings and am now going to start saving $ for that project.

I did re-examine the spark plugs and really do not see much difference between the banks. Maybe one bank is a little light on compression? One thing for sure, if it is something going bad eventually it will make itself known.

Now to complete the Comprehensive Comp. Monitor. I thought the Evap.
was going to be the hard one.

 

You may well be allowed at least one unset monitor.

 

You are. Just as long as it is not the Comprehensive Component Monitor test. It seems to be real particular as I cannot seem to get it to set. I think now the problem is that I am probably less than 30% in the gas tank.

(On a side note the 17" Michelin tires I just put on ride much smoother than the P-Zero 18" I did have.)