Confused

[01NavyBlueSLPSS]

So today I installed my factory tune from my predator. When I took it for a drive I noticed rattling noise when I accelerated hard. Sounded like pre detonation. So I re installed the predator tune and now it's gone. So wtf. Why would I be getting pd from my stock tune? Btw the car was dyno tuned at some point before I bought the car. Idk if that has anything to do with it or not. I'm really hoping no damage was done to the engine for the 15 mins that I drove it....

[Knight]

Handheld tuners have been known to cause issues. They usually tend to do more harm than good. I doubt any serious harm was done, but I'd avoid using it again.

[Knight]

As for why it caused the problem, I'd guess that the handheld doesn't take into account any changes that were made to the tune when it was dynoed. It simply adjusts things based on what they would have been set to by GM. In effect, it is over-adjusting the tune, because it doesn't take into account the adjustments already made.

[01NavyBlueSLPSS]

Looks like I can never run my stock tune again. Which sucks because my speedo is off with the predator tune. But the upside is my engine runs cooler

[pajeff02]

What mods have been done? Was it the stock tune or dyno tune saved on the Predator? Most handhelds include speedometer calibration -- check your instructions as I am not familiar with the Predator. The cooler running may be due to recalibrated fan settings if you have a 160 or 180 degree thermostat.

[01NavyBlueSLPSS]

No idea where the dyno tune was saved. The only mode dones to the engine is underdrive pulley. Also, I had the programmer plugged in for live data feed last night, and when I went wot my spark advance jumped clear to 48 degrees on the predator tune. Isnt that waay high?