Hey guys. earlier today on my way from work i was crusing on the highway on my 89 rx7 13b (big street port on boost cut, i just changed the oil from the break in. at this point i already put in 600 miles to the engine)

i keep it on 5th gear around 2500 rpms 57 mph or so. i on my usual highway cruise
im like 15-20 mins into my cruise on my way house and all of a sudden i felt like a yank when the gas is let off and im like wtf? so i look at my air/fuel raito and it has the dashes instead of numbers and i tried giving gas and it started to die little by little on the rpms then when i put it back to neutral it goes back to reading the raito, pretty much goes back to normal. is this something i should be worried about? what do you guys think it is? ( never done this before)

 

I haven't heard of this buy try duplicating in in the same speed and rpm and then try duplicating it at a different speed and rpm. Im thinking maybe the tps is starting to get a dead spot. Another possibility could be the cruise control system might be faulty because you did mention that it went back to normal once you put it in neutral and that's when the cruise control deactivates. Hope this somewhat helps point you in the right direction.
I noticed that you put 600 miles into the rebuild.. I was told the average break in period was 2000 miles. Are you done with the break in period or are you still breaking it in? I have about 800 miles on a fresh rebuild and I'm still going.

 

oh no my cruise control doesn't even work I just keep the old steady foot on the pedal. as for the break in the mechanic told me around 500 miles to do the oil change but I haven't push the engine hard on it either.

 

its turns out my car did the same thing only this time it died on me and left me stranded and it wont even start

 

well, start with the obvious, the basics - fuel and spark. make sure there is ample fuel supply and that the injectors are, indeed, firing. make sure you have spark at the coils and at the plugs themselves. if they check out fine, then check the engine itself. check the compression. 600 miles should be plenty to show an issue with the rebuild, but you never know.

 

Fuel pump failed?

Fuel filter clogged?

Fuel pump wiring hacked up?

If the car sat for any length of time greater than 6 months, then the fuel injectors must be tested and cleaned by a shop. I can't stress this enough. If it sat longer than about 12 months, all rubber fuel line should be replaced, tank flushed, lines flushed, filter replaced, rails flushed, etc.