When I do a power brake start, the first time I did it, it was a good take off. I slowed down to do it again and when I tried power breaking my car just sputtering then went? Tried one more time and same thing, I tried a rolling start and took off great but dead stop it sputtered again, runs fine and everything, any ideas what it could be? It is an auto

 

what engine, what year? could be fuel pressure or flow. test fuel pressure, i would check air filter, fuel filter, spark plugs first. then have a look at the maf if it has one and if its dirty clean with maf cleaner, check intake air motor/valve and clean if needed.

 

94 z28 5.7, just had a tune up and my air filter cleaned, I let it sit for awhile and took it out again and it ran just fine and took off just fine

 

Is it a stock torque converter? Maybe you are just over fueling the engine and getting the stumble from that. The stock torque converter locks up around 1600-1700 IIRC.... on a V-8.... You can only effectively run the rpm up to the lock up point, after that, youre wasting your time and gasoline.

 

as was said above, I'd check the fuel filter, sounds like something might've gotten into it

 

How do you define a tune up? Low RPM launchs will really test your secondry ignition system. If you have a voltage leak (bad spark plug wire or coil) that where it will show up first. Same thing goes with a lean condition but that really should have set a check engine lite.

 

Yeah its running lean for sure, I got ported and polished heads and intake and 1.6 rocker arms and a bbk twin 58mm throttle body with no tune, but over fueling the engine kind of sounds right but I will check the fuel filter and **** too

 

with those mods and no tune i would say thats most of the issue. better get a solomon tune.

 

Lean is more air not enough fuel. Rich is to much fuel. Too much fuel will not cause a miss. It will cause lower power and bad fuel mileage. Lean will cause a miss but your O2 sensor should detect that much lean and set a check engine light. Assuming the O2 sensors are working.

 

Throttle control sensor! There is a simple test to make sure it is or isn't the throttle control sensor. Start you car and let it run. Open the hood and tap the throttle control sensor. If the car's ideal changes while tapping it, you have a bad sensor and it will need replaced.