Okay. Starting off with what's there:

3.0 ecu
350z cams
350z pistons
HR gasket
SSIM + PF tb
51psi static fuel pressure via regulator
3.0 maf
3.0 manifolds + budget Y
VAFC-2 + aem wideband
VLSD swap Stage 2 ACT + fidenza fw

The problem(s)

Rough idle. Its a little more than cam lope to my ears but I could be wrong.

Factory O2's at idle reading way lean. Wideband says 14.8-15.8 bouncing around.

Busting up slightly at partial throttle.

Seems to be underpowered but it may just be my high expectations. It spins at any speed in 1st and hooks up completely in 2nd.

Troubleshooting.

I have raised and lowered fuel pressure. Checked the afr throughout the rpms with the wideband. Adjusted the idle screw. Checked for vacume leaks with starting fluid. Read codes with the huge shop diagnostics tool and found the factory O2 lean issue.

No partial throttle adjustment being attepted by the afc, no performance hurting codes, fresh gas 3 times.

I have not changed the fuel filter in a couple years but I figure the 300z one I put on then should still be fine.

My 3.0 was running great before the swap so I'm doubtfull of any "car related" issues.

Last complaint and issue is that I have no cel. Could be the bulb.

Any help on this would be awesome. Thanks in advance.

 

what are your AFR's ...i could almost bet you are running rich at any RPM besides idle with a 3.0 ECU and 3.5 injectors----you just need a tune

 

its been tuned to 13.3 - 13.0 from 3000 to redline.

 

The thing that gets me is: isn't it suposed to run lean with no tune? I'm at -8 from 3500 to 5800 just to get it to a 13ish:1.

The flashing lean at idle and steady/low throttle is scaring me too. 14.6 to 15.8 is fine for bouncing around but it swings over to above 17 and 18 for split seconds when idling, cold or warm.


Cold starts are terrible as expected though.

 

so i unplugged an injector clip that i had some issues with on the install and the idle didnt change that i could tell. Clipped it back on and pushed down with a screwdriver to clip it in all the way and the idle smoothed out. This was right after a seafoaming and it has lucas ucl in the tank. Ill put some miles on it tomorrow and check to see if the wideband richens up.

If anyone is paying attention to this thread, it'd be nice to get an opinion on the next mod series (engine wise).

ECU (im leaning towards Megasquirt)
Headers (stock 98 manifolds now with Budget Y)
Z33 injectors
50-75 shot (have the nozel and jets already)
BBMAF (PVC hack)

 

I would at least get a set of OBX VQ35 headers.

 

MEGASQUIRT?! Are you serious? Dude come on, MS was made for the early EFI motors that weren't that smart to begin with, slapping on a MS is an insult to the brilliance of our motors and it will NOT be running the same.

 

Megasquirt has come a long way in the past few years. Please do research before you come in and show your ignorance. Software updates for the MS2 have made it a more viable solution for us 3.5 swappers. Honda boys use it for engine swaps and they have just as much or more technology in their engines as we do.

There is one guy on here running MS on a 4th gen from Canada but with ford ignition parts. MS has made the updates to allow our equipment to work with a little programming.

For roughly $200 you can have the same datalogging, timing changes, and fuel maps that you can get with EMU. Standalones are scary, I know. But, if MS can put LSx's into anything with no problem, I'm sure it can handle a vq with the vvt disabled.

 

did you flycut the pistons or use a thicker HG? The rocking of the pistons on a cold block is enough to tap the heads...I'm guessing you're running HR's in a DE

 

got most of the bugs worked out by adjusting idle and just driving the car but the issue with studdering when snapping the throttle is killing me. Any low throttle to higher throttle snaps result in a studder similar to wheel hop combined with a slight bog.

It also is affecting shifts. I can side step the clutch in any gear at redline and its fine but if i rpm match or blip the throttle when shifting it does the same thing as snapping the throttle.

The problem was less apparent with the 3.0 and i think it may have shuddered from a shift once or twice in the 6 years I've owned the car.

I have heard that it could be the MAF but I have put one in the car since ive had it but i cant remember if the problem was there before the replacement. I cleaned it last week and it may have helped with some hessitation in the powerband but no help with the shudder. I have no performance hindering codes and my buddys shop scan tool just shows lean O2's at idle but so does the wideband.

I dont think its gonna be an axle because it would have completely striped or broke by now.

I dont have a cel but that may just be from a blown bulb. (I've never had the cel come on before)

My exhaust from the cat back is pretty rough from previous owner repairs. Small piping and a cheap muffler shop restrictive muffler. I dont think that would cause this much of a problem though.

I used my Fidenza flywheel from my old motor but I'm pretty sure any damage to it is unlikely.

So what would cause the problem to get worse with the 3.5? After changing so many parts (everything from the drivers axle up to the throttle body), what else can i do to troubleshoot?