AEM problem... car gets tuned, runs great, then...

[sepulchralx]

This has happened like 3 times already:

1. My friend tunes the car, afrs at WOT are around 10.8:1 to 11.5:1...

2. The car drives fine, and shows that on the aem uego gauge.

3. When i try to drive the car a few hours later it starts leaning out bad, like getting as high as 12.7 afrs at WOT.

4. So i have my friend retune, then it does it again.

He's thinking its IAT correction issues... whatever it is its really pissing me off. The car either runs too rich or too lean. Anyone know what it may be? I checked the vac line to the fpr its good.. This happens at transition into boost too, not just at high rpm.

God this pisses me off.

Thanks

[the converted]

Most likely IAT or ECT corrections. When your friend tunes have him set all of the corrections to zero, and then adjust them as necessary. Also keep in mind that timing adjustments can also effect the afr.

[sepulchralx]

i dont understand why it would change because he street adjusted it then three hours later at the same ambient temp, the car starts to run leaner, way leaner.

i've got a nice fuel pump and a quest alternator too, i dont think its voltage issues although my speakers do wine with the throttle.

[the converted]

Get data logs from when he tunes it and when it is off to compare and you'll be able to see what is different. On another note it could be wiring issues skewing things off, like bad injector voltage offsets if your driving at night and were tuned during the day.

[sepulchralx]

Get data logs from when he tunes it and when it is off to compare and you'll be able to see what is different. On another note it could be wiring issues skewing things off, like bad injector voltage offsets if your driving at night and were tuned during the day.

u mean voltage being lower because lights are on?

[scarboroughdub]

If the problem is tuning related then your buddy should be able to figure it out pretty quick..

Base timing map is pretty decent, IAT, sensor comp and other comp maps that he may not be aware of.

But mainly check your grounds on the motor. you would be suprised what a bunch of s***ty grounds can do to your sensor readings.

all else fails check wideband.

[the converted]

Yeah, sorry that was kind of two thoughts in one. There could be some wiring issues that are throwing sensors off, and that the voltage of the car could be lower with more electrical demands. I have a habit of turning on the headlights, blower on high, and rear defrost to check the voltage offset tables.