why so lean

S

stumpy

Active LVC Member
Joined
Jul 16, 2014
Messages
91
Reaction score
0
Location
New England
advice time kids, I'm out of ideas and parts to replace

Consistently getting a very lean (+20s) LTFT on only bank1 and only on high RPM.
Eventually stumbles and throws a CEL for P0171 and the random misfire if I keep it pinned at WOT. Idle is fine, cruising is normal.

Replaced much of the intake, including all upper and lower gaskets, plugs, coils, still no change. Thinking of doing the brake booster but that seems fine. Plugs look OK, no oil, no foul.

Haven't smoked it out yet, because this only happens at high RPM, and thats kind of hard to do on this car when its not moving...:mad:
Maybe injectors??
 
could this be a cat issue guys? asking not suggesting (unless im right)
 
Slow (clogged) injector(s)?
Low fuel pressure at volume (clogged filter, clogged pickup, failing pump)?
 
wouldn't a fuel problem with the exception of injectors) throw lean codes on both banks?
 
stumpy said:
wouldn't a fuel problem with the exception of injectors) throw lean codes on both banks?
Click to expand...

Probably. Of course, the fuel line runs to bank 2 and then from bank 2 to bank 1. Still, bank 2 should be have some problems too. Just taking some wild shots at it.
 
Like GRell,I thought catalytic converter,since I had similar symptom with my 3.0 with blocked catalytics. don-ohio
 
Did you ever remove the injectors? If so make sure they are seated properly and no leaks. Otherwise, I would 'lean' towards CATs myself. But go ahead and throw a new fuel filter on it, cant hurt and its cheap.
 
I've heard that code on Fords usually means Vacuum leak. I would start with hoses up and down out the intake Manifold and else where and boots and clamps.

Could be minor until higher RPM being why. Higher RPM more Vacuum air.
 
probably not vac leak, because there is not much, if any, vac at WOT.

sounds fuel related. weak pump, obstructed flow, etc.

do these things have a fuel pressure sensor?
 
marvelous, checking fuel pressure under load should be as simple as using a reader capable of logging the PID then.
 
chris2523 said:
probably not vac leak, because there is not much, if any, vac at WOT.

sounds fuel related. weak pump, obstructed flow, etc.

do these things have a fuel pressure sensor?
Click to expand...

I still say Vac leak. He did not say if its a Gen I or Gen II, 6 or 8 Cyl engine. Happened more than a few times on the 6. The codes on Gen II hardly ever put you in the right direction. You kinda got to look at what's not.

http://www.automotiveforums.com/t572085-codes_p0171_p0174_lincoln_ls_v6_quot_.html
 
An 04 v6
I'm thinking its a dirty cat, maybe injector. I don't have access to a fancy smoke setup so I'm going down the parts list starting from the intake. Right now I have a few electrical/tranny issues as well, but they are unrelated to fuel/air/spark.
Unfortunately the car has been ****ting CELs too long while I've chased this one down (part by part) and is past due for a sticker, so I can't just take it out for a PID report (but will soon try anyway)
 
Sad update:
Car won't start...
Amost certain its the TR range sensor as the CEL has come up with E on the dash during the past month. How hard is this to replace with the tranny still on the car?
 
stumpy said:
Sad update:
Car won't start...
Amost certain its the TR range sensor as the CEL has come up with E on the dash during the past month. How hard is this to replace with the tranny still on the car?
Click to expand...

It is changeable with the transmission still on the car. Be warned that you will need an alignment tool, or to carefully mark where the old one was set to (assuming it was correct).
By "won't start" do you mean that the starter will not even run (no noise from under the hood)? Otherwise, if the starter is turning the crankshaft but the engine isn't firing up, your problem is something else.

http://deneau.info/ls/s6x~us~en~file=s6x71038.htm~gen~ref.htm
 
Starter isn't even trying, and it was throwing a P0708 code when parked. The dash still shows "P".
 
Last edited:
In regards to the lean bank aspect of the thread, could this be as simple as a bad oxygen sensor (or sensor wire) telling you its lean when its not? I think the computer uses this to adjust A/F ratios so it could be incorrectly adjusting itself. I think each bank has a sensor so if one is bad, it will say that side is lean.

As for the TR sensor, I replaced mine in the driveway with the trans in place (on my 02- does gen matter?) and it did not need adjustment. Turns out it wasnt my problem- but it could very well be yours.
 
02LincLS said:
Could this be as simple as a bad oxygen sensor (or sensor wire) telling you its lean when its not? I think the computer uses this to adjust A/F ratios so it could be incorrectly adjusting itself.
Click to expand...

I've replaced both upstream O2s, didn't make much of a difference on the LTFT
 
stumpy said:
I've replaced both upstream O2s, didn't make much of a difference on the LTFT
Click to expand...

Are these injectors vacuum assist? If so, seems like vacuum since its taking out the whole bank. I'm not familiar enough with the setup to know why this wouldn't effect the other side as well.
 
Well some good news, it started with a different key!
I have 4 keys:
2 from the dealer

1 was bought and programmed by myself,
1 is the remote start.

PATS will flash for remote start some of the time, other times it actually works.
for the other 2 keys, the light is off, it just won't crank
:confused:

I'll take it out for a PID report this weekend.
 
You must log in or register to reply here.

Members online

No members online now.
Total: 319 (members: 0, guests: 319)
Back
Top