I've been trying to diagnose this for a while now, but I'm too poor to start randomly replacing parts, so any input is appreciated.

Problem:
Past VTEC at 3/4 to full throttle the engine will start to randomly bog/studder past around 6.5K RPM. Redline is set to 8K, but the revs never get that high without it bogging hardcore. At full throttle from idle till 6.5K it revs smoothly, no hesistation at all.

Current setup:
- B20 VTEC
- new plugs
- new plug wires
- external coil (Nology)
- standalone ECU (Link)
- 440 cc RC's
- Bosch fuel pump
- R cams

Car idles fine, is perfect for daily driving, just when I get on it I have to shift way early and it's killing my fun Car was running pretty fine about 6-8 months ago, could take it up to 8K no problem.
Help in appreciated

 

check your fuel pressure...if the regulator is failing it may be low and in turn when it needs that volume and pressure in the upper rpms its not there.. thats first to check.. let me what the result is

 

check spark plug gap

 

Noted Will check it out.

Oh, I notice my distributor is ticking (RPM dependent) and there is a little oil buildup at the usual place behind the distributor. Could a bad dizzy be the cause? I havent replaced the cap/rotor in about 2 years

 

stuttering at high rpms sounds like a fuel issue (most likely) or ignition

 

i kind of have the same iissue, at full throttle its fine only when i left off to partial throttle it stutters then when i push full throttle its fine and only in vtec.

 

check your igniter.. Same thing happen to me and it was my igniter..

 

when I changed my intake manifold for a stock gsr to a skunk2 I had this problem till I adjusted my vtec crossover point..

 

Possibly ignitor. At around 1/2 throttle I can take it up to almost redline smoothly, but the moment I give it more than that it starts bogging (sounds like its backfiring). Does this rule out the dizzy/coil?

 

Mine only did that at around 11-12 psi boost under full throttle and I gapped the plugs closer.....issue solved for me.

 

will putting 87 octane in a vtec engine cause it to bog at partial throttle in vtec?

 

I agree, sounds like a fuel management issue but I had a problem that sounds similar to "bogging" in vtec and but it only happened when oil was low. Good luck.

 

bump for more help for a good guy

 

i was having that problem also and it turned out to be a connection on my V-AFC was loose. dont know if u have a vafc...

 

No VFAC, standalone here. Currently replacing the dizzy to an OEM unit, we'll see if this solves it