Runnin' Lean.

96TCSig · #1 October 27th, 2009, 10:33 PM

Ever since I bought my TC this summer, I've had a check engine light. I threw an OBD II scanner on it and got a "Bank 2 Running Lean" code. I also have a bit of a rough idle, revving up and down. After clearing the code, it stayed off for about a week and came back. I've put new plugs, wires, fuel filter in it and cleaned the MAF sensor in the last few weeks, but still am pulling the code.
It always seems to be bank 2. So, I'm thinking O2 sensor. Which side of the car is bank 2? Would it most likely be the sensor before the cat or after? Or should I quit being cheap and replace them both?

no0c · #2 October 27th, 2009, 10:46 PM

Quote:

Originally Posted by 96TCSig

Ever since I bought my TC this summer, I've had a check engine light. I threw an OBD II scanner on it and got a "Bank 2 Running Lean" code. I also have a bit of a rough idle, revving up and down. After clearing the code, it stayed off for about a week and came back. I've put new plugs, wires, fuel filter in it and cleaned the MAF sensor in the last few weeks, but still am pulling the code.
It always seems to be bank 2. So, I'm thinking O2 sensor. Which side of the car is bank 2? Would it most likely be the sensor before the cat or after? Or should I quit being cheap and replace them both?

What are the exact DTC's you are seeing?

Bank 2 is the driver's side. (Left, cylinders 5-8)

Replace good parts? Not me unless you know the service record of the vehicle and if the mileage is high enough on the HEGO's, then yes, I would replace both.

Good luck.

white lincoln · #3 October 28th, 2009, 11:01 AM

O2 sensor on bank 2. It's probably best to replace ALL O2's. At $70 ea it won't be cheap but worth it. How many miles on the car?

fshavlak · #4 October 28th, 2009, 12:56 PM

I had the lean condition light come on, for both sides.

Cleaning the MAF fixed it. I'd buy some MAF cleaner and give it a try before I went for the O2 sensors which may or may not be the cause. I like to try fixing possible causes or a problem in order from easiest/cheapest to hardest/most expensive.

Rookie FixItMan · #5 November 5th, 2009, 11:15 PM

Dude, This is not a success story. Had a 94, ran lick a clock. Not one ping ever. Crashed it, and got a 96 TC with 91K on the clock. Lean Bank 2 from week one P174.

replaced IAC, MAF, EGR, downstrean O2 sensors, copper plugs, Motocraft wires, DFPE, flashed the PCM, removed the timing retard pin, and checked vaccuum leaks. Still, throws a code P174 after warming up and running for a while. Only throws code after warming up. Runs better with 89 octane. Better still with 92.

When you find the devil, post the solution here. I'm cursed.

Rookie

KStromberg · #6 November 6th, 2009, 04:29 PM

If one O2 is bad, chances are you will be replacing the other one too. This happened on my 91 Townie. Just replace them all and you're golden.

gadget73 · #7 November 6th, 2009, 04:44 PM

Quote:

Originally Posted by Rookie FixItMan

Dude, This is not a success story. Had a 94, ran lick a clock. Not one ping ever. Crashed it, and got a 96 TC with 91K on the clock. Lean Bank 2 from week one P174.

replaced IAC, MAF, EGR, downstrean O2 sensors, copper plugs, Motocraft wires, DFPE, flashed the PCM, removed the timing retard pin, and checked vaccuum leaks. Still, throws a code P174 after warming up and running for a while. Only throws code after warming up. Runs better with 89 octane. Better still with 92.

When you find the devil, post the solution here. I'm cursed.

Rookie

At this point I'd be suspecting bad injectors if you've also changed the fuel filter with no results.

Rookie FixItMan · #8 November 7th, 2009, 02:59 PM

I had replaced fuel filter, and ran come injector cleaner through the beast. Need to install upstream O2 sensors, which I have purchased, but it's darn tight up there. Also did seafoam treatment. lots of smoke, but no real change in performance. I did replace to octane adjust bar since it did not fix the problem. PCM was flashed before I purchased the car, and I redid it, with no impact.

Derek said it is likely unmetered air. I believe him, but don't know what to look for, or the potential sources of leaks. There must be an answer, I just have not found it yet.

Rookie

no0c · #9 November 8th, 2009, 02:04 PM

Quote:

Originally Posted by Rookie FixItMan

Need to install upstream O2 sensors, which I have purchased, but it's darn tight up there.

BINGO ! And yes replacing upstream HEGO sensors is not an easy task but very doable.

Quote:

Derek said it is likely unmetered air. I believe him, but don't know what to look for, or the potential sources of leaks. There must be an answer, I just have not found it yet.

Sir Dereck is no doubt correct and the vacuum tee at the intake manifold passenger side rear is a good place to look.

See THIS THREAD for info concerning the Tee.

Good luck.

Rookie FixItMan · #10 Yesterday, 09:38 AM

I looked for the "T" when I first got the 96, but the plumbing appeared significantly different from the 1994, and I did not find it. I'll look again this weekend and report back. The "T" in the 1994 was a real problem, old and full of holes. The rubber felt like swiss cheese, and had lost all structural integrity.