Stuttering Up Till 4500Rpm

[Borci88]

Hey guys,

Have a little problem with the latest Skyline I bought. Through any gear from 2500rpm till around 4500rpm it will stutter and make boost but bounce around 10psi up and down as if the power is switching itself on and off. I assumed it was the stock boost solenoid but that is looped and not connected to the wastegate (although still wired in through the plug). It does have a boost tee hooked up and runs 10psi after 4500rpm. Mods are full exhaust system and GReddy front mount but other than that nothing engine wise, I can't put my finger on why it's shuddering until the "supposed" boost solenoid would allow full boost.

Cheers!

[defari]

coilpacks / plugs / vac leak? Is it running rich?

[Borci88]

I know there's a tiny leak in the vacuum hose that runs from the manifold to the rocker cover and that does effect idle from time to time, could that also effect coming onto boost?

[DVS JEZ]

Check what spark plugs and spark gap it has.

What fuel pump does it have? Might need a new one

[Borci88]

Will have a look at spark plugs but I'd imagine everything is just standard spec including the fuel pump, I'd imagine the stock fuel pump could handle 10psi but it is getting a bit old now I suppose.

[Borci88]

Dp

[defari]

plugs should be gapped to .8mm

whilst you have the plugs out, check the coilpacks for cracks - you can tape them up / silicone them however from numerous posts this is only a temporary fix, new splitfires ($500-$600) are well worth the investment. Havent used or researched yellow jackets (cheaper) however if your not going for bullshit huge horsepower then they may be an option if your wallet is light.. oem nissan packs are just as expensive as the splitfires so may as well go with the splitfires..

Id first rule out anything else before forking out for new coilpacks.. it could be a simple fix..

get the vac leak fixed, whether or not its the problem its still a good idea to fix it.. as they say "a stitch in time saves nine"

[Borci88]

Oh forgot to mention, it does have a full turbo back X-Force exhaust but it still has the stock Cat for some reason, could this be restricting flow at all? I don't think it would but I thought it'd be worth asking.

[defari]

how big is the exhaust? do you have a show off valve?

[Borci88]

3 inch from turbo to cat, standard cat, 3.5 inch from catback, bov has been blocked off but it stuttered with standard big blocked or not

[Rolls]

I know there's a tiny leak in the vacuum hose that runs from the manifold to the rocker cover and that does effect idle from time to time, could that also effect coming onto boost?

a tiny leak on vac becomes a massive leak on boost, fix it., almost certainly your issue.

if you are running extra boost from a big exhaust/controller this could be causing havoc with the tune, remove any boost controllers and see if it fixes it, if it does then time for a remap via a nistune etc.

Read the misfire at 4500-5000rpm thread for other suggestions, there are billions of similar problems in that thread.

Edited July 26, 2011 by Rolls

[Borci88]

Cleaned out the AFM and changed the pod to something a bit newer and it has made it run a lot better but it does still stutter a little bit coming onto boost, will have a proper look at that vac leak tomorrow and hope that that fixes the problem.

Cheers!

[Borci88]

Mmm sealed up the VAC leak and it still does it, I'll have to take a video to demonstrate what it's doing. Especially in first it climbs revs but doesn't really go anywhere, might have to watch the boost gauge next time but it just accelerates like an NA.

[Rolls]

how did you seal the leak ?

[Borci88]

how did you seal the leak ?

Packed in silicone, was rubber fitting to the metal head and seems to have sealed it, no hissing anymore, will check on it tomorrow after a proper drive and hope it hasn't melted.

[Rolls]

Take it off and cut the end off the hose and refit it properly, you don't silicone vacuum hoses lol, you just cut them and fit them properly with a clamp.

[Borci88]

It's not the hose it's the rubbery fitting for the hose that's wedged into the block