Hello, ever since i got my aeroforces i have been scanning a few different parameters and realized my LTFT has been around -10 to -14 while cruising. From my understanding, its supposed to be around 0 while cruising? Under WOT it does drop down, but usually not above -4. The 02 reading fluctuates a lot at cruising, but at WOT locks in just above 900mv. My MAF readings are generally in the higher 3000's. The RPMS of the car seem to be fluctuating quite a bit at idle too, but there doesn't seem to be any misfires. I have a zzp 1.0 tune and no egr or cat and pacesetter headers. Could this be caused by a vacuum leak? Thanks.

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A vacuum leak usually causes you to have a higher positive LTFT, not a negative one.
I forget where you live, but it could partially be due to wide outside temp changes.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

IIRC Vacuum leaks tend to give you positive LTFTs and exhaust leaks will give you negative LTFT's. Before I found the crack in my crossover pipe, I always had negative LTFTs. Then when my downpipe gasket was leaking, I had negative LTFT's. Later my EGR had a leak and the same thing, negative LTFT's. About 2 years ago, I had a vacuum leak in the SC Bypass valve, this time, my LTFTs went way positive.

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3.5" MPS, 1.84 Rockers, 3" DP, Frt PEM, 39lb Injs., PowrTuner, Wizair
14.07@ 98.85mph 2.180 60'

Your O2 senor readings sound correct. They move around a lot on these cars. Your LTFTs might be off due to ZZP tuning there pcm's to a little on the rich side. A custom tune for your car might solve your issue. Positive LTFTs means the car is running lean and the computer is adding fuel thus the positive numbers and negative LTFTs means the car is running rich and the computer is pulling fuel thus the negative number.

Milestone

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thanks for the quick reply guys. I do have a nasty exhaust leak just before the rear y pipe, and I'm pretty sure I also have an exhaust leak on my crossover and the exhaust manifold gaskets are probably leaking. Sounds like I got a weekend project on the way!

Also, I have a few quick questions. Will negative LTFT have any bad effects on the engine in the mean time until i fix this hopefully tonight and tommorow, or is it still good to drive. I have probably been driving it like this for about a year so it can't be too bad... Also, around what is a normal IAC during idle and WOT? Mine seems to sit around 9000 at idle and jumps up to around 30000 at wot. my ignition timing is around 27 degrees when cruising, but when i let off the gas it goes up to about 45 degrees, is this normal?

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Well, time for a little update. I sealed most of the exhaust, including new felpro gaskets on the manifolds, and a some modifications to the crossover and Y pipe to seal up the headers. Now my LTFT locks in at 0 all the time at WOT or anytime i get on the gas, otherwise its around -14 to -19 at cruise or idle I am a little stumped on this one now. I am going to try unplugging the EVAP, I heard that can cause the trims to go - too... Other than that, I am at a loss.

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