As you all might have heard, I drove my baby from MN to NC over new years...well on the way (in Chicago)my car threw a few lean codes and then I got the dreaded wrench light. I cleared the codes and decided to reload my custom tune...I plugged in my Diablo Predator and low and behold the performance tune option was there, but my custom tune option was gone!!!

So I played with it the best I could...I got it running for a while and then I got to Kentucky where I finally gave up. I called Doug who told me to Max it out on the Rich side or both 2-4K and 4-7K and that seemed to get us to NC ok.
With Doug being so helpful I decided to go ahead and buy his tune right whenI got to NC, the tune is awesome, but I saw that when I floored it the car would shutter, stutter and hesitate..if I took my foot off and accelerated gently there was not a problem. I thought this was maybe a issue with the tune..me and Doug have gone back and forth trading tunes and me trying them. But no matter it seems as though as soon as I step on the GAS to the floor in 3rd and 4th gear the car just shudders until you let off. Does anyone have any idea what this could be?

As a side note my predator fried yesterday(would not boot) so my shop is getting it replaced but if there is something I can check in the meantime it would be great.

By the way im not throwing any codes at all...even after t shudders like that...strange huh?

 

there was a thread I read a few weeks back about a variable cam sensor/valve or something. That did some wacky type codes, and also had a crazy shudder when it failed. Not sure where its at, but maybe someone else will remember what I am talking about and have a link to that thread. He got it fixed at the dealer.

 

I drove my DiabloSport 93 Octane tune to Denver from Milwaukee. I called Diablo and they told me to take out 2° of advance as the octane in Colorado is 91 due to the altitude and at WOT it may hesitate and knock.

I never had an issue. I have been home and put on over 6K miles. I did add the 2° back when I got home.

I'm sure Doug would recognize this type of situation, so maybe having the hardware checkout out for the freak sensor failure isn't a bad idea.

 

Any other ideas??

 

There have been some issues with throttle bodies causing odd problems.

 

This also sounds like a possible fuel pressure problem. There is a known TSB on the fuel pump, especially after extended driving periods. Could this be a severe example of this problem??

 

The predator will always lose any custom tunes whenever you return it to stock so you either shouldn't ever return it to stock or keep a laptop with your custom tunes with you.

I learned this the hard way when I detuned mine to tune a friends car at the track. I reinstalled it on mine thinking I'm just going to reload the tune and it wasn't there.

 

I would think it was the Fuel Pump TSB, but this can happen right when I start up and go down the road and open her up... I dont have to be driving for any extended period of time. Unless the bubbles stay there and never go away in which course I would thik I would get it at lower RPMs as well.

Like I said this doesnt happen until I put the pedal to the floor in 3rd or 4th gear.

 

Definitely sounds fuel related, either bad fuel pump or pressure sensor or something like that. sounds like the engine is not getting enough fuel at WOT.