b18a1 surging at speed...

[EFDX]

cruising at highway speed 3000-3500 rpm the engine surges about 50 rpm every 2 seconds or so. it seems to have a rythem to it. the engine seems to run good otherwise. it has done it since the install (90si h/b) about 3 weeks ago. any ideas anybody?

 

[78civic]

What 'install'? Give more detailed info..

New cap/rotor/plugs/checked the wires?
New fuel filter? Adjustable regulator that wasn't 'adjusted'?
Orig pump with over 150k miles on it?
Engine/trans grounds free from paint (sometimes peeps get all goofey with the paint and restrict 'good' grounding)

Change/swap ECU with a goon known one.

E

 

[EFDX]

it's a 90 si hatch with a 91 b18a1, new dizzy, new sparkplugs, new wires, new fuel filter, straight swap, engine has DC 4-2-1 headers, no cat, 2inch pipes into a flowmaster muffler, grounds are good (no paint/rust)
what is an "Orig pump"