car breaking up at 5500 on dyno

[Nothinspecial]

Hello,

I have a blacktop s14 sr20det with a tunning issue. so heres the info.

I ran road atlanta in this car and it made around 330 hp at 19 lbs of boost. The car had a wiring issue and thats why i couldnt make more out of the car before the event but this was soon fixed the day before the event which made the car run better and i believe made more power. The issue was the mail coil pack plug on the wiring harness had a faulty connection. anyways.

I go now last week to tune the car up better and just clean the tune out and the car mess's up. All the wiring is great now. but the car was getting tunned and then all of a sudden the alternator died. So then after replacing it we make another pull and the car breaks up at 5500. No boost leaks, no vacuum leaks and the timing is point on.

So then process of elimintation came in. We ran the codes on the ecu. only thing that came back was the knock sensor. So we figured it was pulling timing. changed it out and nothing changed. then changed the cam angle sensor just to make sure. and nothing there too

The car is getting fuel and the car runs very strong untill it hits 5500. The engine was rebuilt professionally and has great compression in all cylindars. we did forget one thing though. We did not switch out the maf.

Could this problem been from a faulty maf? I would figure it wouldnt go over 3000 if the maf was bad. So any thoughts or info would help.

thanks

[novita1021]

I'm having the same when its cold it pulls all the way to 7k when its warm its like runs out of breath or something at around 5500rpm..did you figure it out?

[KiLLeR2001]

Coilpacks. I had a similar issue, everytime I hit around 5k RPM it would start breaking up. Otherwise the car ran fine.

[HYPNOTIK]

What plugs are you using/what are they gapped at? Check all your coilpacks?

[ray666]

definetly check plug gap. also hows your a/f ratio?

[Nothinspecial]

air fuel is spot on, the plugs are gapped correctly, and ive tried diff coil packs. no luck so far find the issue :/

[Nothinspecial]

well my buddies z has a fuel cell like my car. and he was having kinda of the same problem. but what solved his was that the fuel pump had to be located below the fluid levels of the fuel cell itself. his solution was that the pump was some how getting air in the line by being mounted this way. so he relocated it and now it runs fine. im hoping to try this solution on my car.

anyone else hear of this kinda of problem with the fuel pump location.