• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Lean code issues


kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
I have been battling lean codes for 8 months now. Two different shops, the dealership, and myself have replaced everything from the Mass Air flow sensor to the fuel pump assembly. I am at my wits end not to mention my billfold is taking a big hit. I checked the PID and what it said is below. Does it point to anything?

Engine RPM 923/min
Ignition Timing Advance 16.5
Intake Temperature 58 C
Fuel System 1 Status CL
Fuel System 2 Status ---
Engine Coolant Temperature 96 C
Calculated LOAD Value 40.0%
Air Flow Rate From Mass Air 6.20 g/s
Flow Sensor
Absolute Throttle Position 16.9%
Oxygen Sensor Output Voltage 0.170V (B1-S1)
Short Term Fuel Trim (B1-S1) 10.9%
Short Term Fuel Trim – Bank 1 9.4%
Long Term Fuel Trim – Bank 1 25.0%
Short Term Fuel Trim – Bank 2 9.4%
Long Term Fuel Trim – Bank 25.0%
Oxygen Sensor Output Voltage 0.405V (B1-S2)
Short Term Fuel Trim (B1-S2) 99.2%
Oxygen Sensor Output Voltage 0.095V (B2-S1)
Short Term Fuel Trim (B2-S1) 11.7%:headbang:
 


RonD

Official TRS AI
TRS Technical Advisor
Joined
Jun 2, 2012
Messages
25,291
Reaction score
8,296
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Welcome to TRS :)


Yes, the Long Term Fuel Trims(LTFT) at 25% are whats causing the Lean codes on both banks
They can take awhile to come down even after you fix a problem, like a few weeks.
OBD readers can't clear LTFT, I think Ford Dealers can but not sure

After engine is warmed up, and idling, unplug the IAC Valve, 2 wire connector
RPMs should drop to 500 or engine may even stall, either is GOOD, it means no vacuum leaks.
If idle does not drop then you have a vacuum leak, upper intake because it effects both banks of the engine.

If RPMs drop then no vacuum leaks, but I would hook up a vacuum gauge to the engine and see what you have
18-21" of vacuum is expected at idle
Now open throttle wide and then let is snap closed
You should see a QUICK drop to 0" then a QUICK climb back up to 18-21"
If its slow to drop and/or slow to come back up, you have a clogged exhaust, and this will cause Lean codes, especially for LTFT
You should also notice a lack of higher RPM power with partially clogged exhaust.

Unless engine is pinging/knocking you are not actually running Lean, just FYI

Exhaust manifold leaks can cause False Leans, but a long shot to have BOTH manifolds with leaks, and O2 sensors would be long shots for the same reason, bot failing at the same time would be very very long odds.

Rear O2, after Cat, can effect LTFT, but these rarely need to be replaced, not never, but you should get a separate code for this one.

The lean and rich codes are about computer calculations and that they are wrong, lean codes mean computer has calculated less fuel should be added based on airflow and RPMs, but O2s are telling it more fuel should be added, so it does add more fuel.
If the % is off by enough then computer sets the codes

Yes, lower than expected fuel pressure can set lean codes because computer expects at least 50psi pressure so it can calculate how long to open each injector, if its 30psi then less fuel comes in and computers calculations are off, and it has to add more fuel

Do you know if Ford Dealer reset LTFT to 0?

MAF sensor will effect both banks, and usually Lean code is the result, but I am sure thats been checked
The air tube from MAF to intake needs to be air tight, or a perfectly good MAF sensor won't be reporting ALL the air coming in, its not a vacuum leak but same result, unreported air is coming in.

PCV Valve can sometimes do the same, it is a 'controlled' vacuum leak but it can stick open.
 
Last edited:

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
Thanks for the information. The MAF sensor has been replaced twice. I do not know if the Ford Dealer reset LTFT to 0. What does LTFT stand for? The engine is not pinging or knocking, but some times when the engine is warm and I start it the engine will stutter and shake but smooth out when I hold the gas down. This is very intermittent. It has also not started at all once again very intermittent I will pickup a vacuum gauge and try see if the can determine is there is any issues. The dealership has replaced 4 fuel pumps in the last 6 months so I actually worry there is not enough voltage to the fuel pump or when they replaced it somehow they clogged the fuel filter.
 

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
Possible vacuum leak

I have found a very small grey hose coming off the heater control valve. Could it cause a vacuum leak? I have uploaded a picture. Also when I pulled the connector from the IAC the idle dropped about 250 RPMs
 

Attachments

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
checks after Long Term Fuel Trim Reset

I reset the long term fuel trim and checked the readings again. Note that the Short Term Fuel Trim (B1-S2) is at 99.2%. What do I need to check for that?

Engine RPM 896/min
Ignition Timing Advance 17.5
Intake Temperature 36 C
Fuel System 1 Status CL
Fuel System 2 Status ---
Engine Coolant Temperature 98 C
Calculated LOAD Value 34.9%
Air Flow Rate From Mass Air 4.87 g/s
Flow Sensor
Absolute Throttle Position 16.9%
Oxygen Sensor Output Voltage 0.725V (B1-S1)
Short Term Fuel Trim (B1-S1) -1.6%
Short Term Fuel Trim – Bank 1 -1.6%
Long Term Fuel Trim – Bank 1 0.0%
Short Term Fuel Trim – Bank 2 0.0%
Long Term Fuel Trim – Bank 0.0%
Oxygen Sensor Output Voltage 0.665V (B1-S2)
Short Term Fuel Trim (B1-S2) 99.2%
Oxygen Sensor Output Voltage 0.105V (B2-S1)
Short Term Fuel Trim (B2-S1) 0.8%
 
Last edited:

telsar

Member
Joined
Jun 23, 2017
Messages
57
Reaction score
4
Points
8
Location
Houston TX
Vehicle Year
93
Make / Model
ford
Transmission
Manual
Run some marvel mystery oil in the gas tank. 2 ounces per 10 gallons. Or fill the tank and add 4 ounces. See what happens.

Sounds like a huge vacuum leak. If you idle at 3000 rpms does the fuel trim decrease a lot?
 

RonD

Official TRS AI
TRS Technical Advisor
Joined
Jun 2, 2012
Messages
25,291
Reaction score
8,296
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
LTFT is long term fuel trim
STFT is short term fuel trim

STFT is instant feedback of the "open time" for the fuel injectors.
The computer calculates fuel injector open time based on RPMs, Air Flow(MAF), Throttle position, air temp, and engine load.
And that calculation is 0 fuel trim
Computers calculation is to make the air:fuel mix at a 14.6:1 ratio
This is a WEIGHT RATIO
14.7 POUNDS of air to 1 POUND of gasoline
14.7 grams of air to 1 gram of gasoline

Computer Knows the weight of gasoline and it is programmed for the Fuel Pressure, so based on that it calculates the OPEN TIME for each fuel injector to get 14.7:1 ratio based on the air flow, the WEIGHT of the air coming into the engine.

After the calculated 0 STFT is burned the computer gets O2 voltage, if its low then computer raises STFT to 2, and thats and increase of 2% of open time, computer check O2 voltage again, if still low it changes to 4%
And so it goes until O2 sensor voltage is at .4v
All this happens in under 2 seconds, its a very fast correction

If STFT gets over 15% for a length of time, 10-20 seconds, computer will set a lean code but not turn on the CEL(check engine light), this over 15% must reoccur a few times to turn on the CEL


Over the life of a vehicle, rings get worn, seals start to leak, fuel pressure can go down a bit, and thats why there is LTFT.
Long term fuel trim sets a bias to computers calculations, so 0 STFT includes LTFT
If LTFT is 5% then computer adds that extra open time to fuel injectors calculation at 0 STFT.
So its a pre-trim compensation for Long Term use as things change on a vehicle.

It is also used on cold starts before O2 sensors warm up to 650degF, and can be used to set STFT
This is why it can't be cleared easily, because it is needed for an engine to run well cold

LTFT is an average of previous STFT averages but it also includes Cat O2 averages as well
And STFT is reset to 0 at each cold start, then biased by LTFT , so if LTFT is 15% and STFT is 5% thats 20% longer open time for each fuel injector.

Your LTFT is 25% and then STFT is 9% so thats 34% longer open time so computer set the lean codes to tell owner there is a problem with its calculation, they are 34% off
 

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
Run some marvel mystery oil in the gas tank. 2 ounces per 10 gallons. Or fill the tank and add 4 ounces. See what happens.

Sounds like a huge vacuum leak. If you idle at 3000 rpms does the fuel trim decrease a lot?
Both the dealer and two shops could not find any huge vacuum leak. there are allot of new parts that seem to have been only temporary fixes. The automatic version of the ranger has a limiter that only lets you go to 2500 RPMs in park.
 

telsar

Member
Joined
Jun 23, 2017
Messages
57
Reaction score
4
Points
8
Location
Houston TX
Vehicle Year
93
Make / Model
ford
Transmission
Manual
Both the dealer and two shops could not find any huge vacuum leak. there are allot of new parts that seem to have been only temporary fixes. The automatic version of the ranger has a limiter that only lets you go to 2500 RPMs in park.
Then 2500 will have to do or maybe neutral may work.
 

telsar

Member
Joined
Jun 23, 2017
Messages
57
Reaction score
4
Points
8
Location
Houston TX
Vehicle Year
93
Make / Model
ford
Transmission
Manual
Just a few thoughts:

Is this a flex fuel vehicle?
If so that can be the issue, its stuck on the wrong fuel.

Check out some Youtube videos:

Schrodingers Box
https://www.youtube.com/channel/UCnIQ-_hRpyHR68f23dQQHUg

South Main Auto
https://www.youtube.com/channel/UCtAGzm9e_liY7ko1PBhzTHA

Pine Hollow Auto Diagnostics
https://www.youtube.com/channel/UCn4Ifss-t3wMT6VBzQoKPUA

Scanner Danner
https://www.youtube.com/channel/UCrf6f8hn5oy4alB2WXJCIqA

These Youtube channels do actual diagnostics of problems, not just change parts as your dealership and 2 shops have done. I wouldn't go back to them.

The first channel I list is probably the best to learn from.
 

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
Just a few thoughts:

Is this a flex fuel vehicle?
If so that can be the issue, its stuck on the wrong fuel.

Check out some Youtube videos:

Schrodingers Box
https://www.youtube.com/channel/UCnIQ-_hRpyHR68f23dQQHUg

South Main Auto
https://www.youtube.com/channel/UCtAGzm9e_liY7ko1PBhzTHA

Pine Hollow Auto Diagnostics
https://www.youtube.com/channel/UCn4Ifss-t3wMT6VBzQoKPUA

Scanner Danner
https://www.youtube.com/channel/UCrf6f8hn5oy4alB2WXJCIqA

These Youtube channels do actual diagnostics of problems, not just change parts as your dealership and 2 shops have done. I wouldn't go back to them.

The first channel I list is probably the best to learn from.

Yes it is a Flex Fuel Truck. I think the last year that used the Flex Fuel Sensor was 2000. In 2001 or 2002 they used the oxygen sensors and a formula in the Computer to determine that. I took off my battery cables and reset the computer to clear my long term fuel trim which was at 25 for both 1 & 2. That could have reset the flex fuel numbers. That being said I did try to find something on how to test for that but I did not find anything.
 

Fordblue213

Member
TRS 20th Anniversary
Joined
Oct 22, 2016
Messages
61
Reaction score
6
Points
8
Location
New Orleans, LA
Vehicle Year
2000
Make / Model
Ford
Engine Size
3.0
Transmission
Automatic
I had leaking exhaust valves giving the truck a stumble and I had a bad head gasket letting a little coolant into the cylinders and make spark plug ceramics crack which would make the cylinder go dead. It wasn't reading as a misfire, it was reading as a lean code. Since that cylinder didn't burn and use up the oxygen, there was extra oxygen in the exhaust, so the O2 sensors saw that and threw a lean code.

Installed new heads and head gaskets. No more misfire, engine ran perfectly smooth, but after a much longer time, I would still get a lean code.

My aftermarket MAF was making the LTFT's max out to 25% after driving for a while. Swapped back in my OEM one and now the fuel trims are perfect and the truck still runs great.

https://www.therangerstation.com/forums/showthread.php?t=177236
 

telsar

Member
Joined
Jun 23, 2017
Messages
57
Reaction score
4
Points
8
Location
Houston TX
Vehicle Year
93
Make / Model
ford
Transmission
Manual
Yes it is a Flex Fuel Truck. I think the last year that used the Flex Fuel Sensor was 2000. In 2001 or 2002 they used the oxygen sensors and a formula in the Computer to determine that. I took off my battery cables and reset the computer to clear my long term fuel trim which was at 25 for both 1 & 2. That could have reset the flex fuel numbers. That being said I did try to find something on how to test for that but I did not find anything.
You should be able to pull some data pids for the flex fuel parameters using a fairly good odb2 scanner and see what gives with it. Those Youtube channels may address the flex fuel issues that can arise and perhaps how to reset it.
 

kstandri2018

New Member
Joined
Sep 29, 2018
Messages
8
Reaction score
0
Points
0
Location
Palm Bay, Florida
Vehicle Year
2001
Make / Model
Ford
Transmission
Automatic
OK I had the oxygen sensors replaced a few weeks back and the codes have not come back and my truck seems to shift better, but I still have the stumble after the engine gets warm and then sits for about 20 minutes and I try to start it again. When I put it in gear and try to drive it the engine smooths out in about 10-15 seconds. Today it continued and left me hanging trying to get out in traffic. The check engine light flashed for a period of time and then cleared on its own. When I checked the codes I had:
1. P11511 Lack of H02S21 Switches - Sensor Indicates Lean
2. Cylinder 4 misfire detected
3. Cylinder 5 misfire detected

This is different from the bank 1 and bank 2 lean codes. I am thinking about replacing the fuel injectors.
 

Big65

New Member
Joined
Mar 16, 2020
Messages
6
Reaction score
0
Points
1
Location
Tidewaters
Vehicle Year
2001
Make / Model
Ford Ranger
Transmission
Automatic
I've been dealing with this for 2 years. Replaced the vac line to the cruise control, passenger valve cover, pcv, pcv valve and the grommet ( all were in need of replacement). Swapped the down range o2 then it went to both upper sensor being lean. Swapped an upper with no change, did the idle control, egr valve, mass flow, vac leak check of the intake and throttle body, intake tube, egr lines, fixed the oil pan gasket that had pushed out at the front main. Truck starts up fine cold, gets a low idle and heavy stutter on a hot start. I get a litter tick under load on the driver side though it's done that well before this issue.
 

Attachments


Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top