Econobox!

All of a sudden on the way home from work, my car won't rev smoothly under about 3K rpm. It doesn't matter if it's under load( driving) or un-loaded (neutral), it shakes until you hit about 3K and then it 'clears' itself. I'm almost afraid that it's the fuel pump/filters that i decided not to change a year ago coming back to bite me in the ***. Any other things to check before I dish out the $$ for the filters and/or pump?

AudiSport4000

See if its pumping enough fuel to the fuel distributor.
How are your ignition components?

Merkin

try unplug the o2

Econobox!

Not running an O2 sensor.

mt6127

if the pump wasn't making enough pressure you'd have a hard time revving or would stall under load. I'd look for something that would impact the mixture or the burn rate like O2 sensor, temp sensor, possibly a FI pressure regulator etc - but my first stop would be to inspect the air boot, vacuum hoses and ISV... Next I'd check the plugs for fouling, the wires and the rotor and distributor cap (a good trick is to mist the wires and cap with water then start it in a dark garage - Little blue arcs are bad... Then I'd move up to sensors like the O2 and temp - last I'd suspect dirty injectors so throw some injector cleaner in the fuel tank...

Econobox!

All plugs/wires/cap/rotor have <3000 miles on them

AudiSport4000

Mine went out a month ago on my 4kq. The car had a horrible time starting and driving in general.

Econobox!

I can try my older, fairly good cap tomorrow.

StormChaser404

Tehn you are in open loop all the time?

Econobox!

I'm not really sure. I had read that CIS-E will sometimes run full rich without the o2, but sometimes run full lean. I've been wondering if 1: that's true, and b: what my car is doing.