I can't clear my check engine light and I have replaced Egr,pcv,O2 sensors, idle air control valve, mass air flow sensor can not find a vacuum leak. fuel pressure is fine I'm completely frustrated can't smog my truck to get tags any suggestions?
Member
I had a similar issue. Ended up being my lower intake gasket.
Have you checked the throttle body gasket? All vacuum lines? I also had one with 2 holes in it that were hidden by the black plastic loom cover. Are you doing the carb cleaner spray or smoke test to try and find the leak.
Have you checked the throttle body gasket? All vacuum lines? I also had one with 2 holes in it that were hidden by the black plastic loom cover. Are you doing the carb cleaner spray or smoke test to try and find the leak.
Member
Had the exact same issue with my 99 2.5, did the same things you did. about a month later my fuel pump took a crap. I replaced the pump and strainer and the code has been gone ever since. I have no idea why this couldve been the issue for my truck other then it was running lean as hell and burning though gas like crazy. I dont have much to contribute but maybe it's something fuel related for you like it was for me?
I did both carb cleaner and smoke test I did find one vacuum leak went ahead and replaced all vacuum lines got about 53 miles on my test drive and check engine light came back on red did smoke test and do not have any visible leaks guess I'm going to have to pull intake off and replace gasket don't know what else to do losing my patience!
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Warm up engine first
Let it idle and unplug the IAC Valves 2 wire connector
Idle should drop to 500rpms or engine may even stall, either is GOOD, it means no vacuum leaks
If idle doesn't drop then there is a leak
Lean code means computers calculated air/fuel mix was lean, not that the engine is actually running lean
Computer was programed for engine size(displacement), injector size(lb/hour), and fuel pressure at injectors
So at any RPM its knows how much air is coming in, so it knows how much fuel to add to get the 14.7:1 air:fuel ratio(this is a WEIGHT RATIO), its Just Math and computers are good at fast math
Computer's calculation is for how long to open each fuel injector to get the correct amount of fuel into each cylinder
There are a couple of sensors the computer needs in its calculation to "fine tune" the air/fuel mix
Air Temp, colder air is heavier has, more oxygen so more fuel needs to be added
MAF sensor, this is similar to air temp but it WEIGHTS the air that passes by it, so if air is cold it heavier but if you were driving at 5,000ft elevation it would be lighter, All air going into the engine needs to pass thru the MAF sensor, and it only "tests" 10-15% of the air flow, so small error becomes a BIG error
A vacuum leak OR any air leak will cause MAF sensor to read lower than it should, so less fuel will be added than should be
That's the air side of things
But there is also the fuel side
2001 2.5l computer expects 55psi fuel pressure at the injectors, there is no fuel pressure sensor
If your fuel pressure is 30psi, then less fuel flows out when an injector opens...................so lean code, computer is having to open injector longer
So what was the fuel pressure?
And you need to raise engine RPMs to 2,500 and hold it there for a minute or two and watch if pressure is dropping, if it is then there is your lean code, lower pressure under load
Lean codes can stay around for a bit even after a repair, Long term fuel trims(LTFT) above +15 will cause the lean codes until the repair causes short term fuel trims(STFT) to go into the -5 to -10 for a day or two which brings down the LTFT under +10
You can also get lean codes from partially clogged injectors, as said lean code comes from injector open times, if an injector doesn't have full flow then computer has to open it longer, so lean code
Try a can of Seafoam in the gas tank or similar injector cleaner
If you get a Bluetooth OBD2 reader or your current OBD2 reader can give you LIVE data while driving you should see STFT -10 to +10 while cruising and LTFT would be above +15 most likely but should start to come down if problem was repaired
After computer does it base calculation it ADDS LTFT to it
Computers base calculation is STFT 0
If LTFT was +15 then STFT 0 is actually +15, and in real time if you see STFT +10 then its actually +25, 10 + 15
Let it idle and unplug the IAC Valves 2 wire connector
Idle should drop to 500rpms or engine may even stall, either is GOOD, it means no vacuum leaks
If idle doesn't drop then there is a leak
Lean code means computers calculated air/fuel mix was lean, not that the engine is actually running lean
Computer was programed for engine size(displacement), injector size(lb/hour), and fuel pressure at injectors
So at any RPM its knows how much air is coming in, so it knows how much fuel to add to get the 14.7:1 air:fuel ratio(this is a WEIGHT RATIO), its Just Math and computers are good at fast math
Computer's calculation is for how long to open each fuel injector to get the correct amount of fuel into each cylinder
There are a couple of sensors the computer needs in its calculation to "fine tune" the air/fuel mix
Air Temp, colder air is heavier has, more oxygen so more fuel needs to be added
MAF sensor, this is similar to air temp but it WEIGHTS the air that passes by it, so if air is cold it heavier but if you were driving at 5,000ft elevation it would be lighter, All air going into the engine needs to pass thru the MAF sensor, and it only "tests" 10-15% of the air flow, so small error becomes a BIG error
A vacuum leak OR any air leak will cause MAF sensor to read lower than it should, so less fuel will be added than should be
That's the air side of things
But there is also the fuel side
2001 2.5l computer expects 55psi fuel pressure at the injectors, there is no fuel pressure sensor
If your fuel pressure is 30psi, then less fuel flows out when an injector opens...................so lean code, computer is having to open injector longer
So what was the fuel pressure?
And you need to raise engine RPMs to 2,500 and hold it there for a minute or two and watch if pressure is dropping, if it is then there is your lean code, lower pressure under load
Lean codes can stay around for a bit even after a repair, Long term fuel trims(LTFT) above +15 will cause the lean codes until the repair causes short term fuel trims(STFT) to go into the -5 to -10 for a day or two which brings down the LTFT under +10
You can also get lean codes from partially clogged injectors, as said lean code comes from injector open times, if an injector doesn't have full flow then computer has to open it longer, so lean code
Try a can of Seafoam in the gas tank or similar injector cleaner
If you get a Bluetooth OBD2 reader or your current OBD2 reader can give you LIVE data while driving you should see STFT -10 to +10 while cruising and LTFT would be above +15 most likely but should start to come down if problem was repaired
After computer does it base calculation it ADDS LTFT to it
Computers base calculation is STFT 0
If LTFT was +15 then STFT 0 is actually +15, and in real time if you see STFT +10 then its actually +25, 10 + 15
