Happy new year to all and good morning .
I have had my V10 scsb 4x4 for about 6 years now , a d finally something has gone wrong .
I say this , because after I have logged over 150k miles , and it having been flawlessly reliable , I am now getting a random bank 1 lean ses light .
By random , I mean I can drive several hundred miles , varying degrees of loads , and not have a check engine e light , then out of no where , light on .
I have read around for a common cause , and pcv hose or valve are a common reply.
I replaced the pcv hose and valve 6 months or so ago , checked it and it is firmly together and in place .
when I watch the live data on my scanner, my fuel trims are quite huge in comparison to what I have seen in the past when the truck was running perfectly .
by huge , I mean stft bank 1 is up in the 30's both positive and negative , while bank 2 is near 15 or less .
I dont remember ltft at the moment , but I seem to remember they were closer to normal in the 1.5 or so positive and negative swing .
This is a 99 with a manual 5 speed .
I dont just throw parts at any problem , hoping to fix the problem .
So now I just need to figure out , where the cause of the bank 1 vacuum leak is coming from ..
Any suggestions would be helpful .
Thanks .

 

Short term fuel trims are supposed to be "all over the place" since they're reacting in near real time to varying conditions. You need to first look at your long term trims to see if they're relatively normal or biased well off from zero and whether or not they are close to each other or there's a wide difference. It is not uncommon for one bank to trip before the other with only a small differential between the trims.

So, check your freeze frame data to get a more complete picture of the conditions when the fault was detected. Posting that data would be useful for continued diagnostics.

 

I had an intermittent bank 2 lean code awhile ago that turned out to be a loose exhaust pipe to manifold connection.

 

I am trying to figure out how to get a freeze frame on my scanner .
I'll keep at that .
When truck als running properly , my trims were pretty close to even both banks .
Right now , the bank 1 is at idle , coolant temp at 187 f.
short term fuel -3.9 up to 0.6 ish
bank 2
-3.0 to 3.0
long term bank 1
3.9
bank
2 6.3

 

As an update , I changed plugs and boots , since it has been a hundred k since last done .
dont know what changed , as I would not expect a plug change to cure the previous lean bank 1 code pro Ken.
But I have no longer had that code come back .
Instead , I have a p1132 code stored , no light.
I have continued to monitor pids.
Bank 1 upstream o2 has been quite different from bank 2 , and the code proves it is lazy .
Fuel trims are along odd between the 2 banks .
Freeze frame shows 31 bank 1 and -4.7 short term fuel trim at the time of the freeze frame
Long term is 14.8 bank 1and 8.6 bank 2

 

I recommend cleaning the MAF.

Faulty air readings will make trims that are ok goofy.

 

I will give that a shot .
Thank you sir .

 

Changed the fuel filter recently?

 

The iat is separate of the Maf on my truck , but I did clean them both ,still same readings
I have not changed the fuel filter in a while ,but do not understand how that would have an effect on only one bank .
O2 voltages also seem to be uneven , which may be because of the code I am getting for upstream bank 1 lean.
I may just change the upstream sensor and go from there .
may also change the fuel filter , when I change the oil this weekend .

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