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Discussion Starter · #1 ·
Ok... so this is the second time I have gotten this code in the last week. I got chipped last wedsnesday and last thursday this code on the way to the stealership to get a new L-hose. I figured it just had to do with the fact the my L-hose was split in two. Replaced the L-hose, cleared the code... as is well. Fast forward to today.... on the highway, cel and "emissions workshop" come on again. Pulled the code with my OBD-2 and came up with P1128: Long term fuel trim, bank 1, too lean. I don't have a vagcom yet (new chip=no money) but my ODB-2 does give me some freeze frame data that the ecu records at the time of the fault:

DTC: 1128
Fuel System 1 Status: Closed Loop
Fuel System 2 Status: Not supported
Calculated Load Value: 25.10%
Engine Cootlet Temp: 167.00*F
Short term fuel trim, Bank 1: 3.91%
Long term fuel trim, Bank 1: 22.66%
Engine RPM: 3240
Vehicle Speed: 75.81 mph

Now what should the normal value be for long term fuel trim (highlighted above in red)? Also, after doing a search, I couldn't find much on a possible fix. The only thing I can think of is possibly another vac line, oxy sensor, FPR?? I did a once over on the vac line and L-hose, but didn't anything to strange.

Any ideas??

Thanks in advance!
 

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Either bad MAFS or 02 sensor (front, heated), or even more remotely bad FPR.
Can you get MAFS readings? I think plus or minus 5% is indicative of
bad MAFS. Is that long term percentage from the MAFS?
 

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I'm going to go with higher pressure FPR needed. Your injectors have run out of room to adjust and are leaning out with the stock pressure beyond what the ECU wants to adjust.

You also may need to clear the codes if long term trims don't clear out when the new chip is installed. I think they would though. Long term trims is comparing new data to old data and seeing how far the adjustment have come. If the fuel needs of the car go up significantly before the old info gets dump you would get this.
 

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Lean conditions are frequently as a result of broken vacuum lines allowing unmetered air into the intake. Check all your vacuum lines between the MAF and the intake manifold.
 

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Discussion Starter · #5 · (Edited)
I'm going to go with the vac lines first. Anyone know the inside and outside diameter? I'm guessing I'll need about 4ft.

I don't know if its necessarily my FPR... unless its going bad, but I don't think it should. I don't want to have to buy one of those yet.

EDIT: Sweet! 100th post woohoo!
 

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Is that O.D. or I.D.? Wow, I wasn't expecting ten feet, but fair enough.
ID, you could get away with less maybe, but its cheap so may as well have alittle extra, hate to come up an inch short on the last hose, know what I mean, you by chance don't go to school up in fargo do you.
 

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Discussion Starter · #11 ·
ID, you could get away with less maybe, but its cheap so may as well have alittle extra, hate to come up an inch short on the last hose, know what I mean, you by chance don't go to school up in fargo do you.
I'll definitely be getting 10 ft and maybe a little more just to have it around. NOpe not in fargo. I go to UND in Grand Forks. I work at the airport in fargo on the weekends though. Are you in Fargo?
 

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Discussion Starter · #12 ·
This is it, definitely bad MAFS.
hmm.... I have some electrical surface cleaner I might try and give the MAF a once over. I have a k&n but haven't recharged the thing since before I bought the VW, so I wonder what could cause a possible failure.
 

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I'll definitely be getting 10 ft and maybe a little more just to have it around. NOpe not in fargo. I go to UND in Grand Forks. I work at the airport in fargo on the weekends though. Are you in Fargo?
Not currently, but that is were I will be going to school as of next fall.
 

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hmm.... I have some electrical surface cleaner I might try and give the MAF a once over. I have a k&n but haven't recharged the thing since before I bought the VW, so I wonder what could cause a possible failure.
K&N filter can cause the MAFS to go bad due to the oil in the filter element. Check out block 2 in engine electronics with your vag-com, see how high you can get the last field to go. A functioning MAFS will peak at 120-145g/s on a stock ECU depending on your model year and HP rating. If your sensor is bad, it will struggle to get over 100g/s. I would not recommend trying to get a max reading too many times (WOT to 5-6krpms) due to your car running lean. (BOOM)

HTH
 

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Discussion Starter · #18 ·
K&N filter can cause the MAFS to go bad due to the oil in the filter element. Check out block 2 in engine electronics with your vag-com, see how high you can get the last field to go. A functioning MAFS will peak at 120-145g/s on a stock ECU depending on your model year and HP rating. If your sensor is bad, it will struggle to get over 100g/s. I would not recommend trying to get a max reading too many times (WOT to 5-6krpms) due to your car running lean. (BOOM)

HTH

I don't own a vag-com, but I"m trying to track one down to run some logs. I'll take a look at block 2 and see what the MAF is reading. I know that the oil from the k&n can cause the MAF to go bad, but the filter hasn't been recharge in last 30,000 miles, so i don't think theres much excess oil in it to cause any problems, but i guess you never know.
 
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