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Discussion Starter #1
I am officially confused now. Here is the data:

Fuel Sys 1: CL
Fuel Sys 2: NA
Calc Load(%): 42.7
ETC(degree C): 85
STFT B1(%): -0.8
LTFT B1(%): 7.0
Eng RPM: 3782
Veh Speed(km/h): 119
MAF(g/s): 23.88
TPS(%): 23.1

What number throws the p0171 code?

Here is my plan based what I have read here (do each item and wait to see if it throws it again):

-Change gas brand
-Clean air filter and MAF
-Look for leaks
-Change O2 sensor

Any other ideas? I will update as things progress. The code comes on every 75 to 90 miles.

A little background on the equipment: I have forced fed headers and strutking's CEL eliminator for P0420 which is not as fancy as the one with the ceramic honeycomb. I have read people whose P0171 has gone away with the new CEL eliminator but on the other hand P0171 is from upstream the post catalyst sensor!!! :wallbang:

Thanks.
 

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Discussion Starter #2
Gas change

Chevron 91 did not work. Still P0171.

Moving on to cleaning air filter and MAF...
 

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Discussion Starter #3
Without strutking's CEL eliminator for P0420, I never got P0171. I kept getting P0420. It may be worth taking that out and see if I go back to P0420.
 

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clean your MAF sensor.....( do you have a K&N air filter ? )
 

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Discussion Starter #5
Don't know about the air filter. Just got this car. I know about the oil getting in the K&N.

What if it is a K&N?
 

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Would the air filter pull P0171 (too lean)? I would think a dirty MAF sensor would yield rich conditions. I'm dealing with a 0171 myself right now...I've got O2 sensors in the mail. I'll let you know how that goes (checked exhaust for leaks, vac leaks, etc...).

Good luck with your 0171
 

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ps - a lot of people have posted about cup airboxes and larini exhaust causing P0171. do you have either?
 

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Don't know about the air filter. Just got this car. I know about the oil getting in the K&N.

What if it is a K&N?
If it is over oiled (which they often are) and even when appropriately oiled the oil can sling off the filter and foul the MAF. It just needs to be cleaned in that case.
 

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Discussion Starter #9
I have stage II with the forced fed headers, I think. Sure about the headers, not sure about the exhaust...
 

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If it is over oiled (which they often are) and even when appropriately oiled the oil can sling off the filter and foul the MAF. It just needs to be cleaned in that case.
YUP ^^^^what he said.
 

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Discussion Starter #11
Replaced the air filter which was filthy with a TOYOTA 0D020-17801 (the USA part number; same as 22020-17801 of the Japan part number). It seems like the oil on the K&N is a hassle for the power gain.

Cleaned the MAF.

Cleared the CEL.

Watching it...
 

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Discussion Starter #14
It is effin back! :wallbang:

I am gonna take the CEL eliminator that I have on the post catalyst sensor out to see what happens. Some people have reported that their p0171 has gone away with a better CEL eliminator.

How do I check for leaks? Is the smoke machine a must?
 

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Discussion Starter #15
My thinking is that if I get my good old P0420 back without the P0171, that means that the installation of Strutking's CEL eliminator in combination with the O2 sensor causes the P0171. In that case I have to spend $50 on the real CEL eliminator with the catalyst honeycomb.
 

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Discussion Starter #17
P0420 is back. Have to not clear codes and drive for a while to make sure that P0171 does not get thrown...I suppose this is a good thing now.
 

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Discussion Starter #18
p0171 is also thrown again. Therefore, I am going to deduce that the CEL eliminator that I was using for P0420 was working and I was not getting P0420 as long as that was on. The P0171 seems to be independent of that CEL eliminator that I was using on the post-cat O2 sensor.

Let the dreaded vacuum leak search begin. If anyone has done this, any tip is much appreciated. Should I remove the rear clam to have better access?
 

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Discussion Starter #19
I have live data plots which I will post as soon as I can connect my OBD-II scanner to the computer.
 

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Discussion Starter #20
On Saturday I am putting some Lucas injector cleaner in the tank and burn the tank in one drive. See if it makes a difference.
 
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