Civic EG

when my rpms reach 3100 there is a sudden grind that last only a split second. it happens when i accelerate and deccelerate.i just installed an apexi vafc and i set the vtec to kick in at 3100 so i think its something with that but im not sure, any suggestions. its a d16z6.

you should never mess with vtec with out upgrading the head!.. your destroying your engine.. set it back to stock or bring it to a dyno for proper tune bro

NEVER touch your vtec engagement point with out any supporting mods. your vtec should kick in as the stock setting of 4500-4800rpm not at 3100

Wow 3100 for vtec engagement! Bad idea.
Anyways that might be your problem. I think stock vtec engagement for d series is more like around 5k some where.

i set it back already and it still does it

you screwed up your head more than likely.

still runs fine. only does it in 3rd through 5th. i doubt i ruined my head.

Oh! only in 3rd and 5th? I don't think I read that part on your first post. Well, it can be a possibility that it can be your tranny if its only on those 2 gears.
Am guessing it only does it at high rpms. Does the grinding sound come while shifting or only when accelerating? And does it feel like the car stops going anywhere while is grinding? If it does feel like the car does feel like it wants to stop going or feel like its slipping then yeah maybe your tranny.

no its in 3rd 4th and 5th and only for a split second at 3100 rpms. i just rebuilt the tranny so thats not it.

Ok I think I probably figured out your problem man.
Do you have an after market exhaust or have you done anything to your exhaust?

What think is that the way the shift linkage is possitioned for 3rd, 4th and 5th gear your exhaust might be touching your linkage and vibrating on to it. It happens to me. But that's cus I have 2 1/2 straight piping. It started with me when I did the new exhaust.