Need Help! Car is running lean

[PoloTeagle]

Hell yes! It could cause that.

If its running lean on the bank with the leak thats the prime suspect. Or lean on the other bank.

The headers are designed to suck exhaust out of your engine, and without getting too technical, they are designed in such away that to optimize exhaust flow and be balanced between all cylinders.

If one side is leaking it's possible that the other bank is scavenging better than the other side... The computer basically doesnt know how to account for that. It assumes equal flow, so its supplying equal fuel to both banks.... It may not be enough to compensate for the leak.

By default O2 sensors arent really used for fuelling calculations at cold startup and idle.

The only thing thats strange is the job of the X pipe is to balance the flow. But yeah fix the leak first and lets see what happens. As of now that's the prime suspect

Update: got under the car and turns out my headers bolts were still loose and were causing a big leak. I guess I never tightened them down all the way. Car is running good now thanks guys!!

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[ugstang17]

Good job. For future LTFT's should always be reading 0 on the Lund display or 1.0 in the datalog after finishing the tune process. They only correct when STFT's stay lean or rich for an extended amount of time and that is a sign there is an issue. Seeing bad readings on one bank and good readings on the other tells you the problem is bank related and not something common to both banks like a MAF sensor. Now you can do your datalogging and get that Lund remote tune dialed in.

 

[PoloTeagle]

Hey guys I’m new to this so bear with me. My car is a 2016 gt and I’ve recently installed a ported 18 intake manifold with lockouts, pmas cai, jlt catch can, and 2m fabrication long tube headers. The car is tuned by Lund. After installing everything my car now runs lean. The AFR is about 27 when I first start the car and then drops down to about 22-23 when idling. The car is throwing a p2195 code. I’m lost on what went wrong. I’ve triple checked my vacuum hoses, cleaned my maf, changed my bank 1 o2 sensor, swapped my o2 sensor extensions from side to side to see if one was bad, uninstalled and reinstalled my intake and still can’t seem to find a solution. Im lost and not sure where to go from here. Any help would be appreciated. Thanks!!

Alright guys im back. I thought I fixed the problem but Lund is telling me I still have some issues after my last data log. I tightened up my headers and now the AFR is reading 14.0 - 15.0 on bank 1 and 14.5 - 15.0 on bank 2. STFT is reading -7 - 9 and LTFT is reading 9 - 14. The car did throw a “system too lean” code but it went away and I’m not seeing anymore codes. The car is idling a lot better than before but don’t know what else could be wrong. I’m half tempted to just return it to stock ‍

 

[ManBearPig]

For future LTFT's should always be reading 0 on the Lund display or 1.0 in the datalog after finishing the tune process. They only correct when STFT's stay lean or rich for an extended amount of time and that is a sign there is an issue

I’m a perfect world, sure. Realistically, you will not see LTFT at 0 under all conditions. Generally speaking, Less than +/- 10% is acceptable and +/- 5% is ideal.

 

[ugstang17]

I’m a perfect world, sure. Realistically, you will not see LTFT at 0 under all conditions. Generally speaking, Less than +/- 10% is acceptable and +/- 5% is ideal.

If LTFT has to impose a correction then your tune needs to be revisited. While it may serve, it is not an optimal condition.

LTFT only changes when STFT extends beyond a preset value for longer than 450mS is there about. If it continues to correct, a lean or ruch condition may be flagged. Below is a reference for diagnosing LTFT's for related issues. Its straight from the 2011 Ford Shop manual.

BTW my LTFT's NEVER change value. I have LTFT's and STFT's displayed continuously. STFT's are changing because as you mention they will in an imperfect world. Any time you apply fuel there will be STFT change until the loop settles and then it will flutter between -3 and +3 99% of the time.

http://iihs.net/fsm/?d=8&f=Adaptive Fuel DTC Diagnostic Techniques.pdf&p=1

 

[PoloTeagle]

If LTFT has to impose a correction then your tune needs to be revisited. While it may serve, it is not an optimal condition.

LTFT only changes when STFT extends beyond a preset value for longer than 450mS is there about. If it continues to correct, a lean or ruch condition may be flagged. Below is a reference for diagnosing LTFT's for related issues. Its straight from the 2011 Ford Shop manual.

BTW my LTFT's NEVER change value. I have LTFT's and STFT's displayed continuously. STFT's are changing because as you mention they will in an imperfect world. Any time you apply fuel there will be STFT change until the loop settles and then it will flutter between -3 and +3 99% of the time.

http://iihs.net/fsm/?d=8&f=Adaptive Fuel DTC Diagnostic Techniques.pdf&p=1

Alright I’m bringing this back up because my car is still having some issues. After fixing my header leak I thought the car was running fine because my AFR finally started acting normal. I sent a log to Brandon at Lund and he told me the car still had some issues so I started looking and I noticed my STFT is between 2-9% jumping around and my LTFT is at 30% at idle. When I drive the car my LTFT starts to gradually go down more and more the higher I get into my rpms. The car is throwing a “system too lean” code now. Anyone care to share their input? Don’t really want to take the car to a shop.

 

[ugstang17]

You have a vacuum leak. This is a classic LTFT symptom of that. Is the LTFT doing this on both banks or just the one? If both banks close to the same with LTFT's rich at idle then you have a vacuum leak common to both banks which indicates it is intake plenum area forward toward the filter. IF it is specific only to the one side then you have a vacuum leak specific to that bank which may be a fuel injector not seated correctly, or an intake O-ring (for no better term) that is failed to seat as well. Either way you have unmetered air getting into the mix after the MAF due to this. You could try an old racing trick which is to obtain a propane torch and with the car idling crack the valve onb the torch just slightly (obviously you don't light it LOL!) and start working it around the fuel injectors and intake runners to the bank the LTFT's are going rich on at idle or the common area if it is happening to both sides between the MAF and intake plenum until the car starts to stall (Propane burns at a much richer rate and when sucked into a point where the vacuum leak is happening it will fatten up the mixture and cause a surge or faulter in the idle. Datalog it while you are doing this and have the logger visible. You may even see the LTFT correct or begin to correct with the additional presence of fuel changing the mixture at the point of the leak and where it gets pulled into a particular cylinder (s). Just don't get over zealous with this process. Don't just crank the knob open. Crack it. If that isn't enough to help locate it then crack it some more. You an always place the propane nozzle near the filter and allow it to pull some in so you can see how the car will respond when the vacuum leak sucks it in. Just stay clear of the air filter area afterwards and allow the propane to clear out before starting the test or you may get a false indication. Hope this helps. I had an old timer race enthusiast show me this trick once.

But who am I? Call Brandon and ask him. He is a great guy. I know him personally. He has done work on my car in the past before he branched out successfully on his own.

 

[PoloTeagle]

You have a vacuum leak. This is a classic LTFT symptom of that. Is the LTFT doing this on both banks or just the one? If both banks close to the same with LTFT's rich at idle then you have a vacuum leak common to both banks which indicates it is intake plenum area forward toward the filter. IF it is specific only to the one side then you have a vacuum leak specific to that bank which may be a fuel injector not seated correctly, or an intake O-ring (for no better term) that is failed to seat as well. Either way you have unmetered air getting into the mix after the MAF due to this. You could try an old racing trick which is to obtain a propane torch and with the car idling crack the valve onb the torch just slightly (obviously you don't light it LOL!) and start working it around the fuel injectors and intake runners to the bank the LTFT's are going rich on at idle or the common area if it is happening to both sides between the MAF and intake plenum until the car starts to stall (Propane burns at a much richer rate and when sucked into a point where the vacuum leak is happening it will fatten up the mixture and cause a surge or faulter in the idle. Datalog it while you are doing this and have the logger visible. You may even see the LTFT correct or begin to correct with the additional presence of fuel changing the mixture at the point of the leak and where it gets pulled into a particular cylinder (s). Just don't get over zealous with this process. Don't just crank the knob open. Crack it. If that isn't enough to help locate it then crack it some more. You an always place the propane nozzle near the filter and allow it to pull some in so you can see how the car will respond when the vacuum leak sucks it in. Just stay clear of the air filter area afterwards and allow the propane to clear out before starting the test or you may get a false indication. Hope this helps. I had an old timer race enthusiast show me this trick once.

But who am I? Call Brandon and ask him. He is a great guy. I know him personally. He has done work on my car in the past before he branched out successfully on his own.

LTFT1 is read 30% and LTFT2 is reading 2% at idle so that it’s bank related?

 

[ugstang17]

That would be correct. Bank 1 would be passenger side. Vacuum is created when the TB is "closed" (command at idle running will be about 1-3%). Obviously as the TB opens the restriction lessons and the draw of the cylinder pistons becomes easier making for a less differential (vacuum) with respect to outside atmospheric pressure. Your passenger side bank is getting unmetered air into it somehow. In fact your vacuum reading at idle on your lcd gauge display may be running less than 15" Hg, however that may be a waited or calculated measurement so don't fully rely on it. On my car idle is between 18-21" Hg after the car has warmed up with idle at 750 RPM and throttle command at 2%. It idles very steady.

Try the process I mentioned with the car at idle using the propane torch. When the vacuum leak is found it will suck the propane in and cause a change in idle (it may faulter or even stall if the vacuum leak is bad enough) and/or you will see LTFT1 begin to correct the opposite way as it see an enrichment and STFT1 will react immediately. STFT1 will react immediately. Remember that as LTFT changes STFT will revert back to 0 on Ngauge display (or 1.00 on SCT device or in datalog).

I suspect you either have a vacuum leak around one of the intake runners, a fuel injector is not fully seated correctly, or teh porting job on the intake may have created a leak. One way to know is to put the factory intake back on and start the car to see if the LTFT changes and Idle and vacuum readings are better.

I don't mean to appear condescending but many people don't comprehend the aspects of vacuum and what creates it. So if I went below your level it wasn't meant to talk down to you.

I just realized you were referring to Brandon at Lund. Sorry about that. I do not know him but I do know that Lund is very helpful. I was thinking of a Brandon at BA Motorsports. Sorry.

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