ALEXZ28

I just got my car put on the dyno, when it was on the dyno it made 275 and it falls on it's face at 4500 RPM. I was told it was the springs, so i changed them today to comp cam beehive springs. I still don't see a difference and it's still cutting back at 4500 RPM. It was a wideband tune not a bolt on tune. What else could be causing this problem? I should of atleast been making about 340 with everything i have done, but it dynoed at 275. I'm clueless as to what else it could be.......

94LTZ

iTrader: (5)

What was the fuel/air ratio around that rpm.. Try putting a fuel pressure gauge on it while on the dyno and see what the fuel pressure does, maybe the pump can't keep up..

ALEXZ28

i changed the val springs and the problem is still there, so cant be the val springs, im changing fuel pumps to 255 see what happens. any other things i can look for, my friends lt1 for 503, bored .30 1.6 comp RR headers, made 349 how in the world am i making 275?????

djjab57

iTrader: (17)

what size injectors are you running ?

sepno77

iTrader: (5)

he's runing stock inj. and stock fuel pump at this time.

djjab57

iTrader: (17)

In that case his fuel pump shouldn't be the problem, unless its just going out.

sepno77

iTrader: (5)

ya i think he should still hook up that fuel pressure hose just to check it tho. his car is idleing wired too. its idles at like 2k when warm and i think when cold it idles really low and car has bin shutting off on him. I honestly think its the tune but he called that guy and the guy says that he tuned his car fine so idk.

ALEXZ28

Ill change the pump see what happens but my friends TA made 500 with stock pump on nitrous

86formula

iTrader: (3)

opti? when i had a loose rotor screw it wasnt noticeable until 5k rpms then it started cutting out

sepno77

iTrader: (5)

you might not have to change the pump, that is the reason for testing it 1st before you spend the money on a new one.

gregrob

iTrader: (8)

Opti?

Mine made my car fall on its face HARD at 4500 RPMS and beyond. Car would just quit pulling and the tach would slow wwwaaayyyy down

ALEXZ28

That's what mines doing, it stopped making power at 4700 made 275 hp after 4700 went to 189 hp and the tach isn't reading right. The man who tuned me told me to buy a tactometer.

KUTTER

Idle speed could be off. Clean IAC.. Bad TPS.. Or as always opti.. Sounds like it could be low res issue, especially at the higher RPMS. When my low res went out it would go clear into the red though wide open with no power loss. Randomly it would die though as you know, from cps just loosing track basically of sensor.Blame your builder I keed I keed man. It still not throwing codes or you dont know? Code 16 and you can bet its that opti.

I dont think its your opti though. IDK why just doesnt seem it. Retard high idle, issues when cold (not hot), hasnt cut off on you. No backfiring,or bucking. Just seems like something else. Without running codes its just guessing. True people had similair issues at higher rpms. But youve gotten on your car numerous times and it hasnt cut out or backfired right?

I still think you have a vacuum leak. I know you said you checked it but it explains most your issues. Idle,Hesitiation,and obviously no codes.And never heard of a opti making car idle around 2k.

ALEXZ28

Yes its. Cuttin off on me, and yes there's back firing while cruising down the road

ALEXZ28

ok i changed the cap and changed plugs (which they looked like crap) the car seems to be running 10 times better all the cap looked like crap and was a little bad. im able to to reach 6 rpm but still doesnt seem like the car is in the 300s. and still breaks up a little. my knock sensor is a little broken and on the dyno, car was so loud being on open headersstarted pulling timing. can the knock sensor kill power?????????????????????????????

95ls1formula

u running the stock knock sensor or an lt4 knock sensor

ALEXZ28

stock..... shes breaking up on top end. knock sensor pulled timing, jw if any one had trouble with this sensor.