I have a 03 f150 with the 5.4, that started out of nowhere started surging (no codes). Came home started checking things out PCV when I would move it it would hiss so I replaced it and the vacuum lines, no change. I cleaned the MAF sensor (with the proper cleaner) it was dirty. Still no change, hooked my scanner up and got 2 codes saying bank1 and 2 are lean. replaced hose going to throttle bottle from the ??? by the brake booster as it was rotten. Deleted the codes it seemed better but not a lot.
Don't know how to add a pic of the scanner that I took, but on the live data of short and long term fuel is
STFT B1 -1.5
LTFT B1 17.9
STFT B2 2.3
STFT B2 0

this is at idle of 636RPM, the LTFT B1 would go as high as 25 when driving, the others would stay a lot lower.

I've sprayed carb cleaner all around the intake, but no noticeable idle change, it idles pretty good. If I put it in gear and hold the brakes and give it gas it shutters pretty bad im still thinking its simple but im sure I'm overlooking something here.

 

You still have an air leak to find.
Did you check out the PCV hose where it goes into the intake?
Crank case fumes sucked through this hose softens the rubber then a hole is sucked inward.
This allows unmetered air to enter.
The OX sensors detect this and add fuel causing the LTFT tables to go out of limit setting the codes and cause poor idle and low speed drivability.
Good luck.

 

I changed the PCV, and all those vacuum lines and the elbow on the backside of intake, only line I didnt change on that is the one water line that goes back and under the intake. I'm going out now and looking for more.

 

Ive been reading different threads about EGR and the DPFE sensor, think Im more confused now lol. When I pull the vacuum line off the top of the EGR there is no vacuum at idle or when I rev the engine up, is this right? I've sprayed 2 cans of carb cleaner on every vacuum line I can get to, at least the top of my motor is starting to get cleaner. I've also pulled a few of the lines off to make sure there was vacuum on them.

 

There is no vacuum on the EGR line at idle and you cannot make it draw vacuum by racing the motor.
Lets start fresh.
What codes are present now so your not chasing past history.
Look at the LTFT tables again for both banks. Don't care what the STFT tables are at this time.
The line through the middle of the block is a coolant line.
Good luck.

 

P0171 is the only code im getting now.
LTFT B1 21.0
LTFT B2 7.8
What I have done is changed out the PCV and hoses that connect to it to the back of the intake and the one going to the throttle body. and the hose from the back of the throttle body to the regulator? next to the brake booster. Also cleaned the MAF sensor (with MAF sensor cleaner)

Went to and had pep boys do smoke test, they came up with nothing. But their scanner also came up with the same code 0171 as mine did. But they did tell me that the 02 sensors are bouncing around too much. He didnt know why, and their master tech is out and will be back tomorrow and he knows more about the readings on them.

 

LTFT B1 and STFT B1 are showing your issue, supported by the code 171.
Since it is only one bank, check the output operation of the B1 - 1 Ox sensor for switching by looking at it's voltage swings compare to B2 sensor that is near perfect acting.
There maybe an air leak in the exhaust ahead of front B1 front Ox sensor.
What is happening is the OX sensor is causing an 'add' fuel signal because it is detecting to much oxygen in the exhaust content.
If one cylinder were misfiring it would be sensed as adding air without fuel if it's injector were faulty but that would set a misfire code you don't indicate you have.
If a bank one cylinder intake port has an air leak it can cause the same result.
Anyways you get how this goes now.
Your looking for a bank 1 issue only and 'not' something common to both banks like a fuel filter,, mass air meter etc.

Good luck.

 

Alright, if I understand what you're saying is it's possible that I have an exhaust leak weather it's a gasket (donut or manifold) or maybe even a cracked manifold? The guy did say the oxygen sensors numbers were bouncing around. He didn't really know much about reading the numbers, their master tech was off today. I have been hearing a slightly different exhaust tone for a few days prior to this, especially taking off.

Just went back and reread what you wrote, so possible intake leak? or did I read that wrong? it's getting close to my bed time and somethings arent making sense right now. And the bank 1 is driver or passenger?

 

Bank 1 is passenger side.
Good luck.

 

I had the same code with a shutter/misfire. Changed the coils and the problem vanished.

 

First of all thanks for this site and to all for there help. I am new but looking forward to giving and receiving advice. Now for the problem.

Mine is very similar to the above quote. Would it be possible to have a intake manifold gasket leak but not be able to detect it with propane, starting fluid or make shift smoke machine?

Throwing lean codes on bank 1 and 2. Truck is a 02 f150 fx4 with 160k. Checked all vacuum lines, including the notorious 90 behind the throttle body. MAF and EGR are operating normally. Fuel pressure is 32 psi at idle and jumps up if i goose the throttle. Fuel pressure reg is operating normally and if take off vacuum line fuel pressure jumps up to 41psi like it should. IAC is only year old as I was chasing this problem last year. MAF also checks out along with IAT sensor. All new motorcraft plugs and coils. Old plugs were built up a little and white from being lean. New fuel filter.

I got frustrated enough to take it to an AWESOME trouble shooting mechanic that has a high dollar scanner to look at all the sensors. He advised to change upstream 02 sensors as they were a little sluggish. Changed few days ago but no joy. He advised intake manifold gasket next.

My LTFT 1 and 2 vary from +15% to +29%. The other day they came down to +10 and truck idled smooth. No idea why came down. Now they are back to the higher numbers.

Everything points to vacuum leak as because I rev the engine to 2500 rpm and the LTFT go down considerably. Truck seems to really lack power up slight incline in overdrive light on the throttle. If i get on it, there is plenty power. I only get codes in winter but suspect probably running lean in summer just not bad enough to trip codes. I cant detect a vacuum leak though and I am banging my head against a wall. Sorry for the rambling. Any help would be greatly appreciated!

 

You still have an air leak.
The LTFT are both out of normal range because the leak is 'common' to both banks.
That puts the leak in the intake system at a common point for both banks.
Both Ox sensors are detecting the same leak so it's not the Ox sensors.
Put a scanner on and do the spray while looking for a sudden change in short trim values.
The leak is not very big or the idle rpm would be way off.
If you see about 636 rpm, it's not very far off from the normal 650 rpm.
Good luck.

 

Thanks for the reply bluegrass! I have done the scanner/starter fluid/ STFT check and didn't notice anything obvious. Ill probably try again. Either I didn't spray in the right place or the leak is small enough that its crazy hard to detect. However, with the above LTFT/ codes i would think it has to be a decent leak, but I am no expert.

Not sure why the LTFT seem to vary randomly. I thought might have to do with expansion/contraction depending on the temp of the motor varying the vacuum leak but there doesnt seem to be a correlation. The LTFT can be at 21 when the engine is hot and next morning on start up it will be the same. STFT tend to stay around -3 to +5 but can go higher at times just idling.

Any thoughts on the intake gasket leaking doing this? I will gladly change it but dont want to if dont need to.

Forgot to mention that there are no noticable exhaust leaks on either banks. In fact I just fixed bank 1 manifold/studs/gasket about a year ago. and new pcv valve.

I will check my rpm at idle on the scanner tomorrow. If only my problem was a dry rotted 90 like a lot of the guys on here

I just know its not running the same in the lower rpm/45mph/overdrive range like when I got it 3 years ago. Thanks for your help so far!

 

Ok so last night I did some more tinkering and I believe made some progress but would like to get your guys thought on interpreting the findings.

1) If I removed the main vacuum line coming from the throttle body. The one that feeds the EGR, fuel pressure reg and vacuum canister (the one that splits into 3 separate vacuum lines) and then plug the hole that goes into the TB, my STFT on 1 and 2 goes to -10 to -7.

2) If I plug the main vacuum line back in and just unplug the fuel pressure reg and plug that vacuum line, then my STFT on 1 and 2 goes to -6 to -4.

3)If I have everything plugged in as normal and shoot a good amount of propane (i am desperate at this point, even risking a small explosion) in near the intake manifold on bank 2, then I can get the bank 2 STFT to go down to about -10. If I shoot the propane on bank 1, I can get the STFT to go down about -5. I hit the EGR valve by itself with propane but no results so I think its not leaking there.

Any thoughts? I think I have to have a least a intake gasket leak but not sure what to think about results 1 and 2, well I have my thoughts but sure yours are better.

And to add more confusion, this morning (30 degrees outside) after driving to work, I was looking at the scanner at idle and in park, the my STFT were around +38 and LTFT were are around +25. If I revved the engine the LTFT went up this time instead of down as usual (like it should with a vacuum leak) I still think I have to have a vacuum leak of some sort! Any thoughts would be MUCH MUCH appreciated!!!!

 

Curious if anyone has figured out his problem. This is also very similar to the problem that I'm having. I've changed every thing that this thread has mentioned, (minus the intake manifold/ gaskets) I've tested for vacuum leaks etc..

All the data that this quote referenced to me sounds more like a clogged exhaust system. Probably the cats. Normally when you have 2 sensors from the same bank fluctuate at the same rate that indicates that the cat is not doing its job. I'm wondering if anyone reading this has replaced their cats and fixed their idle issue. I'm considering doing mine, but with how expensive that is I don't want to guess. Unfortunately, every shop / stealership I go to always refers the problem to the intake, iac, eger, pcv, vacuum leak, gasket leak crap that does NOT fix the issue if replaced.
The only difference is, my truck does not throw any codes.

Let me know if anyone has fixed their problem by replacing all 4 of their cats (2 off each bank). I want to know if this is the next step and I'm tired of people telling me the problem is from something I've already "fixed" or addressed.