I've been giving my baby a very good, much needed overhaul... most notably switching from a Craptech to SFMU and redoing all pipes/plubming/hoses. The SFMU is the only real difference in the whole setup. Well, right now I've got the car running extremely rich and getting it ready for the dyno one final time for actual tuning (took it last week), and...

While parked, in neutral, and not moving... If I slowly raise the rpm's from idle to redline (to check for smoothness), I consistently get an immediate drop at ~5200rpm's back down to ~4700rpm's each and every time. My fuel pressure is strong and unchanged, but my A/F gauge (at ~5200rpm's) goes from a steady 'all the way rich' instantly to 'all the way lean' until the rpm's (quickly) drop back down to the ~4700rpm's, and then resumes 'all the way rich' until ~5200rpm's again. I can sit there and do this all day long, and it's very precise and consistent on every try.

Now, if I go WOT and floor it, I can go through the entire range of RPM's without any problem (while still parked/neutral). It's acting just like a rev limiter, and I can see the fuel cut back it back down.

I had to leave this morning for work and didn't really get to try anything yet. I intend to check the voltage of the MAP sensor, clean out the ML, and see if it acts this way while in gear/moving on the road. SOoooooooo... Am I going nuts? (quite possible, never experienced fuel cut before)

DSM Registry:
http://www.dsmregistry.com/137

Setup in a nutshell:
MANUAL TRANSMISSION
8.8:1 block, 3 angle valve, port/polish
440cc injectors, Vortech SFMU, Walbro Pump
Apexi SAFC, Missing Link, Hallman mbc
HRC S16g, Greddy Type-S Bov, Starion FMIC

- J

Sounds like a fuel cut but im very unexperienced with turbo so wait for some other responses.

possibly a misfire hard to tell. Start by checking gap and condition of plugs

Originally posted by 420agreenvilleSC
possibly a misfire hard to tell. Start by checking gap and condition of plugs

New plugs, freshly gapped... besides, I would expect a misfire to be through the entire rpm spectrum. Instead, this is occuring at precisely the exact same rpm, and nowhere else. Am I wrong?

- J

Any other ideas? Am looking forward to the morning...

::updated::

I just wanted to take a moment to say a word about a certain fellow at the shop... I'm not sure when he was born (didn't take the time to ask), but he inexplicably died today shortly after confessing to screwing around w/ my SAFC. My car ran great through the entire rpm range, and now (low & behold) it doesn't.

- J :censored

hey i had the same problem when i was N/A but then i but the turbo on it and it ran fine...do u have turbo cams? do u have a turbo?