First off, the car is a 1996 z28 auto. The motor is bored over, ported and polished head and headers. Everything else is stock. The motor seems to have a slight surge or sputter around 50-60mph. It idles smooth, low end has plenty of power. But around 50mph it starts to have a slight surge and doesnt run as smooth. Does anyone have any idea what the problem might be and what i could do to fix it? Any help is greatly appreciated! Thanks.

 

is it tuned for the heads a headers? Also, you may need a bigger cam in order to properly use those headers.

Another problem could be a bad tq converter not locking up.

 

Have you checked all the basics?

1) 02 sensors (solved my problem which after my eng rebuild turns out I needed to replace the originals) Mine was doing pretty similar, sputtering, surging, loss of power around 45-55 mph.

2) Of course have you checked the infamous OPTI, wires, plugs, etc? Assuming so since you rebuilt your eng.

3) did you have PCM tuning after the eng rebuild/head work? Stock eng maybe you didn't need tuning but headwork, and depending on the other mods you've done, it could very well help.

4) finally have you had your codes read like at Autozone, etc? May save you a lot of time and it's free.

 

Thanks so far!

The car has not been tuned. I originally thought this was the problem, but I have no idea where to go or what to do to tune. This is the frist newer car that I have modded. My last was a 68 camaro.

I did change all of the o2 sensors and all of the ignition components have been checked.

 

As long as the heads were not home ported you can go with a generic tune from PCMforless or MADZ28..