Light throttle jerking issues

[AngryRB]

Light throttle jerking issues

Hey guys, had my RB3025 neo tuned and runs great except for on very light throttle where it starts jerking.  I've had the tuner look at the low load points and says the pwr fc is old model and most likely the problem.  I'm gonna have a road tune done also to try find out more but can anyone suggest anything else that can cause jerking.

So some stairs of setup

2530neo, 3076, 44mm tial, z32 on 4inch pipe, gfb recirc BOV set soft, pwr fc, avcr, 1000cc experts, 416 walbro, stock reg, 

One thought was I had to weld up the r33 throttle vacuum hole as it wasn't compatible with the neo mani.. not sure how important that is..

[AngryRB]

Anyone have a suggestion? Seems much worse when cold

[Ben C34]

I assume you don't have a wideband? 

It could be lean.

[hardsteppa]

Jumping between load points would be where i'd start; one of them needing adjustment.

[Dose Pipe Sutututu]

Your throttle enrichment table isn't setup correctly.

[AngryRB]

Looks like I need to get a wideband to shed some light on what's doing.  How do I access the throttle enrichment part of pwr fc, I could screen shot it.

[Dose Pipe Sutututu]

It's called "ACCELER." and the screen looks like this.. unfortunately it's upside down (got it off Google).

You will need a wideband and see what the AFR is like when you jab the throttle vs. RPM. Of course too rich will stumble, too lean will stumble.

Column 1 = RPM
Column 2 = how much fuel in ms
Column 3 = how long in ms

Because you're running larger injectors than stock, I would say reduce the amount in column 2 by the percentage of your injector size increase.

So OEM is 370cc right? now you have 1000cc or so.. that means you would only need 37% of the original throttle pump values.

Play around with it, however you will need a wideband.

 

[AngryRB]

Thanks mate, will see how that goes ..

[Die$eL]

My MR2 turbo does this. When on light throttle it misfires. 

I replaced just about all of the vacuum pipes. It's much better now but still not 100%. I still have the replace one pipe that comes into the cabin. Hopefully that sorts it.

[Trex]

Did you find a resolution to this? @AngryRB 

[AngryRB]

1 hour ago, Trex said:

Did you find a resolution to this? @AngryRB 

The tuner had it a week for cold start and cruise adjustments and has improved alot, said it was running quite rich and needed new plugs.  It seems to go jerky after a bit of a flogging and not so much when normal driven.. Ive been told its likely the power fc and the injectors being so big. Be interesting to put a haltech in but cant justify the coin.