Rb25det problems-please help (a bit technical)

[gdubsmsp]

Alright, heres the deal, i have a series one rb25det that is currently pulling all the ignition timing out from 5800-6300 rpm, then puts it back in and it pulls hard to redline. This problem only happens under load-not just free-revving. We connected and nissan consult computer to it the other day at work and monitored all the sensors possible while driving it. The maf reads good, the fuel trim reads right on, the o2 sensor is reading good, the coolant temp is good. Pretty much at 5800 rpm the ignition timing goes from 33-40 degrees btdc to 0 degrees and the motor runs like **** all spittin and buckin till 6300 rpm where all the timing comes back (33-40 degrees) and the motor pulls hard to redline. The only thing i am unable to tell is if its pulling timing due to knock becaused even the nissan consult does not have a knock counter, but i do not hear any knock and i dont understand why it would put all the timing back in if that was the case, plus before putting the motor in the car i pulled it all apart and checked all clearances so i dont think anything is knocking. By the way, the motor is all stock except 3" exaust (no cat), fmic, and 10 lbs boost with a greddy profec b. Please let me know if anyone has heard of anything like this or has any ideas.

[240z4u]

Sounds like false knock, although I am not sure why it would be pulling so MUCH timing.

try unplugging the knock sensors, this isnt a permanent solution but if there is a change its a place to start

Evan

[Carl H]

check base timing but believe it or not, thats the way the ecu is mapped.check for leaks in the intake track.

[eh?]

Any codes? Is the boost spiking? Are the knock sensors hooked up?

[gdubsmsp]

I disconnected the knock sensors and test drove it, pretty much no change other than a slight bit weaker overall im sure due to a weaker ignition map.

i also checked intake tract for leaks-nothin. By base timing do you mean just watch it on a scanner or actually get the timing light out.

On top of it all, there are no codes, and with the profec b there are really no spikes.

[eh?]

Make sure base timing agrees with consult timing. No unusal sensor readings prior or during the misfire? (tps maf cas?) How does it run with stock boost?

[gawdzilla]

By base timing do you mean just watch it on a scanner or actually get the timing light out.

you need to use a timing light. if the CONSULT is like the PFC readout (90% sure it is) it has no idea what the "real" timing is. It assumes the timing is set correctly (e.g. 15 btdc on the consult is 15 btdc on the timing light). The consult could be thinking you're at 15 btdc when your car is actually running say 20 btdc, always showing 5 degrees retarded from what you really are running. You need to make sure the CONSULT timing is matching what you're seeing on your timing light/crank pulley.

[gdubsmsp]

it doesnt matter what the boost is set to, it does the exact same thing. I am however having an issue with my boost controller (profec b) that no matter where i set it i am getting over 12 lbs of boost just after the misfire when it runs from 6300 to redline but thats AFTER the misfire. Even when i set the controller to factory boost, i still get 12 lbs, but its not spike cause it stays there. Other than that all the other sensors read right in range during the misfire.
Modified by gdubsmsp at 2:42 PM 2/29/2008

[gdubsmsp]

tomorrow ill dust off the old timing light and see what kind of damage i can do with it. thanks