Does this confirm a Vacuum leak?
02-01-2018, 07:22 PM
#1
Does this confirm a Vacuum leak?
So I took a look at the readings off my scan tool, and I noticed that there is an issue with my fuel trims. Now there are no DTCs, and the truck is running better than ever, it feels very powerful and no misfiring or noticeable loss of power.
My STFT is fine for both bank 1 and bank 2 (about 3-5 over a negative number).
However, my LTFT is high for both banks. Both banks idle at 21.6 (when it's warmed up properly) and also tend to change over to a negative number. Both banks have that identical reading and they stay consistent when at idle.
From what I've read, this could be either a vacuum leak, a dirty injector, or a bad/dirty MAF sensor. I took my MAF out and cleaned it well, that wasn't it.
I also heard that having a non OEM PCV valve causes issues. I swapped it for a rotorcraft valve and reset it system by unhooking the negative terminal for 30 minutes. This did not fix the problem.
I read that if the LTFT number goes down to normal when I hold it at 1500 RPMs, that confirms a vacuum leak. I tried it and indeed it went back to normal while in that RPM range. Obviously the number also goes down while I drive, so it's high at idle.
Does this confirm that I have a vacuum leak? Or is there something else I could be missing?
My STFT is fine for both bank 1 and bank 2 (about 3-5 over a negative number).
However, my LTFT is high for both banks. Both banks idle at 21.6 (when it's warmed up properly) and also tend to change over to a negative number. Both banks have that identical reading and they stay consistent when at idle.
From what I've read, this could be either a vacuum leak, a dirty injector, or a bad/dirty MAF sensor. I took my MAF out and cleaned it well, that wasn't it.
I also heard that having a non OEM PCV valve causes issues. I swapped it for a rotorcraft valve and reset it system by unhooking the negative terminal for 30 minutes. This did not fix the problem.
I read that if the LTFT number goes down to normal when I hold it at 1500 RPMs, that confirms a vacuum leak. I tried it and indeed it went back to normal while in that RPM range. Obviously the number also goes down while I drive, so it's high at idle.
Does this confirm that I have a vacuum leak? Or is there something else I could be missing?
02-01-2018, 08:29 PM
#2
Senior Member
iTrader: (1)
Since both banks are reading the same its safe to assume a vacuum leak. Check out the pcv elbow that goes around to the rear of the throttle body elbow.
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joe8512 (02-02-2018)
02-02-2018, 03:55 PM
#3
02-02-2018, 08:13 PM
#4
Senior Member
Not how I confirm a vac leak, there's a much easier way. However, looks like you succeeded...congrats!
You mentioned a loose hose on bank 2 ? I'm not sure what that means lol. Well, I can only guess your referring to a breather leak ? Since it's the only hose one may signify as bank 2 IF a division in the vac system existed....
I imagine you referring to bank 1 and 2 as right and left side of the engine...must be what your thinking. Correct, but 1 and 2 aren't split for vacuum, -just so your aware.
Btw, which hose was it Joe?
You mentioned a loose hose on bank 2 ? I'm not sure what that means lol. Well, I can only guess your referring to a breather leak ? Since it's the only hose one may signify as bank 2 IF a division in the vac system existed....
I imagine you referring to bank 1 and 2 as right and left side of the engine...must be what your thinking. Correct, but 1 and 2 aren't split for vacuum, -just so your aware.
Btw, which hose was it Joe?
02-02-2018, 10:03 PM
#5
Not how I confirm a vac leak, there's a much easier way. However, looks like you succeeded...congrats!
You mentioned a loose hose on bank 2 ? I'm not sure what that means lol. Well, I can only guess your referring to a breather leak ? Since it's the only hose one may signify as bank 2 IF a division in the vac system existed....
I imagine you referring to bank 1 and 2 as right and left side of the engine...must be what your thinking. Correct, but 1 and 2 aren't split for vacuum, -just so your aware.
Btw, which hose was it Joe?
You mentioned a loose hose on bank 2 ? I'm not sure what that means lol. Well, I can only guess your referring to a breather leak ? Since it's the only hose one may signify as bank 2 IF a division in the vac system existed....
I imagine you referring to bank 1 and 2 as right and left side of the engine...must be what your thinking. Correct, but 1 and 2 aren't split for vacuum, -just so your aware.
Btw, which hose was it Joe?
It was the one here that dips under
02-02-2018, 10:08 PM
#6
Senior Member
How did you get a pick of my engine ? That's mine without a doubt...cool lol. Btw, that's a VERY old pic of my engine...I don't think I have that picture anymore lol.
Anyway, not sure which one you mean. Are referring to the mini hose harness (colored vac tubes) or the breather hose off the intake ? The intake hose are IAC (on top) and Breather (on bottom).
Anyway, not sure which one you mean. Are referring to the mini hose harness (colored vac tubes) or the breather hose off the intake ? The intake hose are IAC (on top) and Breather (on bottom).
02-02-2018, 10:18 PM
#7
How did you get a pick of my engine ? That's mine without a doubt...cool lol. Btw, that's a VERY old pic of my engine...I don't think I have that picture anymore lol.
Anyway, not sure which one you mean. Are referring to the mini hose harness (colored vac tubes) or the breather hose off the intake ? The intake hose are IAC (on top) and Breather (on bottom).
Anyway, not sure which one you mean. Are referring to the mini hose harness (colored vac tubes) or the breather hose off the intake ? The intake hose are IAC (on top) and Breather (on bottom).
I googled 2000 f-150 5.4 intake assembly to show you and that picture was one of the first to pop up lol
