The car shuts down soon as i get on the gas.Once it hits 4400 rpm the fuel injectors shut off and the car stops pulling.The car is supercharged hittin only 5 lbs at 4400rpm.I have a granati maf and used a stock maf to see if it would fix the problem and it didnt.Any advice is appreciated thanks!

 

Are you sure its not just a plug gap being too wide. Are you around .030" gap? Service engine light on? Changed anything recently?

 

highly doubt ur injectors are "shutting off"

 

95maroboi:
As onefastmx5 suggested, check the plugs. The AC platinum plugs are notorious for "losing" the pucks which means the gap will be ~ .080" instead of the stock .050". He's right, the gap needs to be tighened up. also, if you are still using the stock 24# injectors then you are at or close to open all the time at 4400rpm and 5psig ... 100% duty cycle ... that's all the fuel they can flow. You need larger injectors and PCM programming changes for them and advance changes just because of the boost, (Just in case you haven't reprogrammed yet) and those changes would be before using the nitrous!!

 

The spark plus are gaped at .032.No service light on.I have plenty of fuel injector left im running 42 lb injectors.I never had this problem before.I took the supercharger off to be rebuilt and put it back on and now theres this problem .Ive checked if it was the maf maxin out but it isnt.The car has been dyno tuned.If i work up to 44 rpms it pulls nice but if i gun the throttle down the engine stops pulling completly and the injectors shut down untill i let the throttle go.

 

Sounds like a quality setup that had been in use ... sorry, not seeing inj or pgm info in your sig I thought this was a new setup with teething troubles. If a scanner shows 0 pulse width for the injectors is the IAT and water temp numbers in the PCM normal. Some people have had strange engine operation if one of those goes bad. Anything odd about the MAF signal ... temp or gms? On reassembly could a wire have been pinched? Perhaps the TPS rheostat is going bad or it's connector or power wire isn't right. I wish I could be more helpful.

 

ok so i just ran a scanner on my car and the map volts and maf numbers arnt matching properly.Ive tried changing my maf back to stock from a granatelli and still have the same problem

 

95maroboi:
Just in the event your MAF frequency vs rpm tables have been corrupted I can PM the stock tables to you if you need them.

 

We could be having the same problem, my car just seems to "shut down" or "break up" around 5k Can you describe what it's doing? Mine also starts at 5psi.

All that aside what type plug are you running? What type of inlet do you have? Could it be colapsing?

 

You got enough fuel pressure? If you don't, and you slam the gas pedal, it will fall on it's face just like you described.

 

man i cant figure it out.The car doesnt have any power when i put the pedal to the floor it just shoots to 44k rpm and the injectors go off and the car wont accelerate at all but if i work the pedal to the floor it pulls hard untill it gets to 44 then once again it the injectors shut off.this is frustrating.

 

95maroboi:
When the tune was done, could the "fuel cutoff 1st Gear or 2nd to 6th" rpm values been mistakenly changed to 4400? Or the "fuel cutoff speed" value changed to a speed close to where 4400 rpm is?

 

I don't know if this has anything to do with your problem, but I was watching a you tube comparison of multec injectors vs the bosch III (motron) injectors earlier. They were all put on a flow bench and as the guy turned up the fuel pressure, the multec style (what most of us have) completely shut off. They quit just under 80 psi, but were fresh. Maybe an older injector might quit under less pressure, just a thought. However this video is definitely worth the 3 minutes to watch if your ever thinking about replacing an injector in the future... Good luck!

link: http://www.youtube.com/watch?v=7oTirEZNRw8

 

The same thing happened to me when I was running a high pressure fuel pump, 6lbs of boost, stock injectors, and a FMU. Once the FMU pinched off the fuel lines, the fuel pressure would rise to the point where the injectors couldn't open against it. It's called injector lockup. The stock pump couldn't achieve the high fuel pressure so it was never a problem with it, but the aftermarket pump did. I think the lockup pressure was around 75 or 80psi if I remember correctly.

I ended up putting larger fuel injectors on the car and putting an inline adjustable pressure regulator on the FMU (in the vacuum line that goes to the FMU) which I adjusted to 4psi, and tuned the car accordingly. This worked, but eventually I removed the FMU and tuned the open loop fuel mixture without it using a new MAP sensor that could read positive pressure.

I had started with the PowerDyne 4.5psi system with FMU. I then bought the 6psi pulley for it and that's when the first trouble started. Apparently the 6psi pressure on the FMU pinched the fuel off enough to cause the problem. With the 4.5psi pulley the fuel pressure only rose to around 60psi. My high pressure pump was capable of around 100psi if I remember correctly.

-Dave C. '97 Z28

PS: Just read MysticBowties response... same thing.

 

The engine that i have in the car has less then 2k miles on it.I have an adjustable fuel regualter on the car.I dont have the fmu on the car because i bought 42 lb injectors and are in no need for it.When i first had the car done and built and tuned it was working great and would shirt at 6k no problem.I took the blower off to have it rebuilt and soon as i put the blower back on it this problem started happinging.So i went to go have it dyno tuned 2 weeks ago and my tuner for 15 years couldnt even figure the problem out.Could it be a bad opti? my fuel pressure is around 43 at idle and 50 wot.and i have plenty of injector duty cycle left.Ive tried bypassing the ignition switching the ignition control moduel and the maf and none of those seem to be the problem.