'91 240sx low rpm stumble

[NateDogg]

Hey all,I have a '91 240sx with: custom 3" short ram intake, 2.5" exhaust, ASP pulley, JWT ECU, Walbro 190lph pump on stock injectors and a Nismo FPR at 34psi (stock). Timed at 20-22 degress BTDC. The engine idles ok at 750 or so. AIV completely removed and hole plugged.

When I shift into 2nd from 1st I sometimes get a stumble for about a second and then it picks up. Somtimes it won't do that if I drag the clutch into the gear. But if it's a perfect rev-matched gear change it hesitates. Engine seems to have decent pull. Also seems like it happens moreso when the engine is cold..

I have cleaned everything and there's no codes of course. All the sensors check out ok. I added a few engine grounds and that didn't help either.

I have a couple of suspects:

1) fuel pump is pulling too much current for stock wiring2) water in gas3) O2 sensor: I read in a search i did about a guy with the same problem. BUT I get pretty good mileage. About 350-400 mi/tank

What do you think it could be?? Thanks.

[NISTECH]

take a good look at your EGR system, make sure its in working order and be sure its not hanging open momentairly, To check your fuel pull off you hose to the rail and turn the key to the on poistion and pump about 30ml into a clear container and let it sit for awhile. you looking for a defined seperation in the fluid.

[NateDogg]

Thanks Nistech but it turned out to be an oily ground near the back of the head to the firewall. Can't believe it!!