Dad's '55 Merc

Hi everyone, I'm new to this but here we go. I've done an ls swap in my dad's 1955 Mercury and it seems to be doing ok except for a little glitch around 1,800-2,000 rpms. If I hold the pedal perfectly still it'll hold for around 5-7 seconds and then dip slightly and come right back up. I've had it dyno tuned and replaced the tps with no improvement. Maybe the iac or a computer issue? Any thoughts?

bigpat1802

Vacuum leak?

Old Geezer

iTrader: (3)

Time to data log it, when it does this....