Hi yall, so I am at a total loss at what could be causing the issues, but basically my car runs slower than it should. However, when I reset the ECU, the car regains it's performance again. This does not last at all however; when I drive the car for a while after the ECU reset (>25 miles), it begins to lose performance again..

I know for sure the ECU is detecting something it does not like, but I can't pinpoint what exactly. (Or I f**cked with the throttle body some how when I cleaned it, car idles normal tho).

Some things I already did / verified:

• Cleaned MAF
• Cleaned Throttle body
• Replaced Coils with Hitachi (fixed misfire)
• Replaced Sparkplugs with Iridium IX (fixed misfire)
• No Check Engine Light.
• Idle is normal (~650 rpm)

Also fyi this engine is SWAPPED, and the swapper checked that the compression is to spec (Engine has 117k miles after swap) and oil consumption is normal for age (.75 qt for every 1700 miles). I highly doubt anything mechanically related problem is causing this.

For reference, I have an Infiniti M35, basically same as 03-04 g35 mechanically engine wise (Vq35de non-revup). Could it be its time for me to get a tune, as the car is running too lean for the ECU parameters? I basically have as much breather mods as you can get/ install reasonably (apart from headers):

• Z tube
• K and n drop in filter
• Z1 Plenum Spacer
• Megan Resonated Testpipes
• Megan Ypipe
• Megan Catback (resonators deleted)

Note: My lack of power began after I installed the k n filter and deleted my resonators

Also I have no way of recording AFRs at the moment. However, I do possess LTFT and STFT at different RPMs

Idle (650 to 700 rpm)

• LTFT B1 = +9.38%
• STFT B1 ~0% (±2)
• LTFT B2 = +6.25%
• STFT B2 = ~0% (±2)

Cruising on Highway (~3000 rpm)

• LTFT B1 = 7.81%
• STFT B1 ~0% (±7)
• LTFT B2 = +6.25%
• STFT B2 = ~0% (±7)

WOT (1000 to 6000 rpm)

• LTFT B1 = goes from 7.81% to 0%
• STFT B1 = 0%
• LTFT B2 = goes from 6.25% to 0%
• STFT B2 = 0%

Extra notes:

• MAF at idle = 3 to 4 grams / sec
• MAF max value = 157 grams / sec
• Ignition Timing advance WOT (1000 to 6000 rpm) = 0 to 45 ° Degrees

Okay I know I just made a post on this but after researching somewhat I am fairly certain the ECU is retarding timing because all the breather mods I got. I never realized how much breather mods I actually put into the car until I listed them in the original post tbph. I have been just steadily increasing mods over time and I guess the ECU had enough lol. Just got to fork over $600 to an uprev tuner.

Firstly did you recalibrate the throttle body (if you unplugged it). If not that might be the issue.

You can check for knock triggers using Torque Pro, or just to rule it out as the issue on your next fill-up add a whole bottle of Seafoam to the fuel, that will raise octane to the point you should be outside of knock (with premium gasoline) on the base timing map.

However, it's always going to try to ride the razor edge of knocking, every rotation it knocks it pulls 1 degree of timing, every 2 cycles it doesn't knock it adds it back up to the maximum timing advance.

You listed +45 degrees advance which is normal so I don't think that's the issue.

Resetting the ECM just resets the LTFT to zero and then it "relearns", it's adding fuel to the point where you are going from a normal fuel mix to the factory-setting of slightly rich. THAT is the power difference you're feeling probably.

Getting a tune will remap to not be quite so rich, the factory tune is definitely leaning towards rich which is SAFE for mass produced vehicles but there's more power to be found by not running quite so factory rich.