P0174 (system lean bank 2) after about 90 minutes of freeway driving

1562 Views 7 Replies 5 Participants Last post by 06b9beca, 10 mo ago

matthewstryker

Discussion Starter · May 23, 2022

Hi Tribeca Community-

We have had our 08 Premier for a a few months, I have done some significant work (pulleys/full suspension/some hoses and most fluids). We noticed that whenever it has been running at freeway speeds for about 90 minutes we are a P0174 (lean condition, bank 2). It runs flawlessly despite the code, but obviously cruise control/traction control get switched off when the code occurs.

After a bit of research I found out that the intake manifold gaskets can leak at high mileage, I got a set of fel-pro gaskets and installed them (yes - removing the intake looks like a 5 minute job... it's actually several hours, especially if you do it the way I did without removing any front belt components). The original gaskets weren't hard, but they did appear to have shrunk significantly over the years on the engine side specifically.

My wife is driving the Tribeca from the Bay Area to LA right now... and the code popped up after 90 minutes (keep in mind she is probably going 80mph+ on I5 with AC on as it's central valley heat).

I read somewhere that in addition to intake gaskets, faulty O2 sensors or a bad MAF can be to blame, but as this only happens when the car has been at 80mph for a good 90 minutes I don't know if that makes sense.

I am thinking that this occurs when the exhaust gets really hot and something expands?
Does anybody know which side is bank 1 and which is bank 2?
Any ideas as to what my next steps should be?

-Matt

Save

1 - 8 of 8 Posts

Flat6er

· #2 · May 26, 2022

right side are cylinders 1-3-5(bank 1), left side - 2-4-6(bank 2).

personally - I would monitor sensors - like lambda sensors (all four), maf, injection timing and length - in one of those long drives... and see are there really changes which could be interpreted as lean or it is just one of lambda sensors acting up.

Save

jimihimisimi

· #3 · Jun 2, 2022

Flat6er said:
right side are cylinders 1-3-5(bank 1), left side - 2-4-6(bank 2).

personally - I would monitor sensors - like lambda sensors (all four), maf, injection timing and length - in one of those long drives... and see are there really changes which could be interpreted as lean or it is just one of lambda sensors acting up.

could swap o2 sensors and see if the issue follows the sensor

maf is easy enough to clean

you could also look at the spark plugs to see if any of the cylinders are burning the plugs

Save

rodomallard

· #4 · 10 mo ago (Edited)

Did you have any success in fixing this? I am having same exact problem, car runs great but codes pop up after some highway driving, except I get P0171 and P0174, both banks running too lean, which to me implies that it's not necessarily the o2 sensor, unless they both failed at the same time. 2008 with 110k miles. I might try and replace the intake manifold gasket, is there a guide on doing this? I have done a little bit of work but am not super experienced.

When this issue first started I found a giant crack in the big plastic air chamber piece that leads from the intake and MAF to the engine, which I replaced with an OEM replacement and the problem went away for enough time to pass inspection, however, the dreaded codes came back after a while. I also ran two rounds of Techron fuel injector cleaner and cleaned the MAF and still nothing. I ran a friend's smoke machine on it and wasn't able to find anything specific, though I'm not really a pro, so while all signs point towards vacuum leak, I haven't found one yet.

See less See more

Save

rodomallard

· #5 · 10 mo ago

Flat6er said:
right side are cylinders 1-3-5(bank 1), left side - 2-4-6(bank 2).

personally - I would monitor sensors - like lambda sensors (all four), maf, injection timing and length - in one of those long drives... and see are there really changes which could be interpreted as lean or it is just one of lambda sensors acting up.

What is the best way to monitor these sensors and is there a guide for normal operating ranges? Thanks so much.

Save

Flat6er

· #6 · 10 mo ago

for normal ranges - probably FSM can help.
basically - you can either log these sensors with some kind of obd2 adapter and phone/computer.
or use a laptop with kkl cable, tactrix cable or even that obd2 adapter.
and, actually, there is option for tactrix adapter - configure sdcard and just plug it in and go for that drive.

for sensors to monitor - I would add IAM, ignition timing and camshaft control (either all 4 avcs if you have 3.6 or avcs and avl if you have 3.0).
(it's more like ranting - if you are willing to do, but you need more like step-by-step guide - let me know, I might be able to help).

Save

rodomallard

· #7 · 10 mo ago

Flat6er said:
for normal ranges - probably FSM can help.
basically - you can either log these sensors with some kind of obd2 adapter and phone/computer.
or use a laptop with kkl cable, tactrix cable or even that obd2 adapter.
and, actually, there is option for tactrix adapter - configure sdcard and just plug it in and go for that drive.

for sensors to monitor - I would add IAM, ignition timing and camshaft control (either all 4 avcs if you have 3.6 or avcs and avl if you have 3.0).
(it's more like ranting - if you are willing to do, but you need more like step-by-step guide - let me know, I might be able to help).

Thank you so much!! I have a basic code reader but I bought a more advanced Bluetooth one and I'll see what I can monitor and if I can find these ranges within FSMs. I will absolutely not hesitate to reach out with what I find or other questions.

Save

06b9beca

· #8 · 10 mo ago

rodomallard said:
Thank you so much!! I have a basic code reader but I bought a more advanced Bluetooth one and I'll see what I can monitor and if I can find these ranges within FSMs. I will absolutely not hesitate to reach out with what I find or other questions.

Please add your vehicle's year to your profile or signature. Forum Rule.

Save

1 - 8 of 8 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month