Tryin to figure out why I have PO 171 & 174 Codes

[0'Lightning]

I decided to make a thread about my problem rather then hijacking the "tuner..." thread anymore :icon_surprised:.

[0'Lightning]

There is supposed to be a gasket there :icon_eek:

Thats what I thought! but could that cause the codes?

[TXLIGHTNING]

Thats what I thought! but could that cause the codes? I don't know if it would cause codes but I would put a gasket in there and see if it clears it up.

[In2deep]

Im in the same exact boat as you are both codes have popped up on me last night and wont stay off, i checked for leaks, tighten everything again???? Is it a bad tune i have a tuner?????

[0'Lightning]

Im in the same exact boat as you are both codes have popped up on me last night and wont stay off, i checked for leaks, tighten everything again???? Is it a bad tune i have a tuner?????

What do you have done to your L?

If it comes down to it im thinking about just buying a few feet of vaccum hoses and replacing them all if I cant figure it out. Maybe I have a hair leak or something. I do have over 100k...
It's weird cause it didnt come on untill the day I got my new 4# crank, plugs, PCV, and JLP 12" intake.

[In2deep]

What do you have done to your L?

If it comes down to it im thinking about just buying a few feet of vaccum hoses and replacing them all if I cant figure it out. Maybe I have a hair leak or something. I do have over 100k...
It's weird cause it didnt come on untill the day I got my new 4# crank, plugs, PCV, and JLP 12" intake.


6# pulley, plugs, port polished super, sct 2400 maf, k@n full intake sct tuner

[tiffo60]

What do you have done to your L?

If it comes down to it im thinking about just buying a few feet of vaccum hoses and replacing them all if I cant figure it out. Maybe I have a hair leak or something. I do have over 100k...
It's weird cause it didnt come on untill the day I got my new 4# crank, plugs, PCV, and JLP 12" intake.

check the vacuum boot at the rear of the engine on the lower intake, if you cant reach it with the blower on you will have to remove the blower to get to it.

[In2deep]

Im about to, that is the same piece the oil separator is going to maybe i pulled the back boot off putting it on???? Please god let it be!!!

[TXLIGHTNING]

Im about to, that is the same piece the oil separator is going to maybe i pulled the back boot off putting it on???? Please god let it be!!! No, there is a vacuum boot going into the rear of the lower intake, behind the rear of the blower. And like Tiff said its a pain to get to it.

[tiffo60]

No, there is a vacuum boot going into the rear of the lower intake, behind the rear of the blower. And like Tiff said its a pain to get to it.

yup and you will know it when you grab a hold of it, it will more than likely be soft and could be torn(some how the oil that goes through it breaks it down over time)

[In2deep]

Well driving to carrolton to pick up part, it did not feel torn or squishy

[0'Lightning]

I did just find out I have a 01'+ 90mm MAF. Could this throw the codes with out a tune?

[tiffo60]

I did just find out I have a 01'+ 90mm MAF. Could this throw the codes with out a tune?

im sure it could, but I would think it would be running rough too:confused:

[WA 2 FST]

I did just find out I have a 01'+ 90mm MAF. Could this throw the codes with out a tune?

Yes it could. You get a lean bank code when there is either unmetered air entering the manifold (MAF reads one thing, but the engine is getting more air than it thinks it should at a given load/rpm... thus it tries to richen the mixture at idle/part-throttle and then once it goes beyond its threshold of enrichment, it throws the code), _or_ its just a poor/miscalculated signal to the PCM. This could be due to 1) a poor MAF calibration or 2) a poor idle/part-throttle tune as it relates to MAF/PCM relationship. #1 happens when the MAF is just not giving the signal that the PCM thinks it should be getting at a given load/rpm condition).

Realize that, from my understanding (and I could be wrong on this, as the PCM's have gotten more sophisticated), the O2s are not even looked at by the PCM under WOT. Given they are not wide-band O2 sensors (but just read .0v-.99v) they do not have the capability to measure WOT A/F ratios. They are there to keep everything "clean and green" under normal driving conditions (that being idle/part throttle/coast down). Now, they do have an effect on WOT fuel enrichment based on the idle/part-throttle readings. Right now, you are at +25% b/c that is the max the PCM can richen the mixture at these low-load conditions. Once it goes above this threshold for an extended period, a code is thrown. The PCM sees this and will enrichen the WOT/high-load mixture accordingly.

I'm sure there is more to it than this, and Terry knows for sure, but this is based on my extensive experience with older mid, late-90s PCM functions. I only have a little tuning experience with the newer stuff, but the codes didn't change, and I think I'm pretty close to being on target here.

Did you just add the 90mm MAF, or has it been on there? If it has already been on for awhile, then I suspect you were close to throwing a code before you added the pulley, etc. E.g.: you could have been running +15-20%. Now with the other small mods, it has pushed it over the threshold, and it is throwing a code. If all the vac lines/hoses/etc check out, then you just need to get a tune. That Xcal 2 should also function as a data-logger and you should be able to "see" what the Long Term Fuel Trims (LTFTs) are doing. Terry will easily be able to adjust these by modifying the fuel/MAF tables.

[0'Lightning]

Yes it could. You get a lean bank code when there is either unmetered air entering the manifold (MAF reads one thing, but the engine is getting more air than it thinks it should at a given load/rpm...

...Did you just add the 90mm MAF, or has it been on there? If it has already been on for awhile, then I suspect you were close to throwing a code before you added the pulley, etc. E.g.: you could have been running +15-20%. Now with the other small mods, it has pushed it over the threshold, and it is throwing a code. If all the vac lines/hoses/etc check out, then you just need to get a tune. That Xcal 2 should also function as a data-logger and you should be able to "see" what the Long Term Fuel Trims (LTFTs) are doing. Terry will easily be able to adjust these by modifying the fuel/MAF tables.


Wow, thanks for the info:tu:
yes, the maf hasbeen on there for since I bought the truck a year ago.

Terry said we should be able to do the tunes for my truck around March 5th if hes moved, and the weathers good.

[0'Lightning]

Neither auto zone or O'ryllies had a gasket to go between my MAF and MAF adapter. Should I try a dealership or what? Do they make sheets of gasket material so I could just cut my own out?

[L8 APEX]

Neither auto zone or O'ryllies had a gasket to go between my MAF and MAF adapter. Should I try a dealership or what? Do they make sheets of gasket material so I could just cut my own out?
I use a thin smear of ultra black pookie.

[TXLIGHTNING]

Neither auto zone or O'ryllies had a gasket to go between my MAF and MAF adapter. Should I try a dealership or what? Do they make sheets of gasket material so I could just cut my own out? I have cut out my own gaskets many of times when I had my old mustang. But if im not mistaken that gasket is made of some type of rubber..?


I use a thin smear of ultra black pookie. Or you can go this route :tu: Whats up TC :beer:

[Mark #2]

Do they make sheets of gasket material so I could just cut my own out?
Yes, and then put black pookie on it.

[tiffo60]

Autozone or Orileys sells sheets of gasket material