RB25 problems

Discuss the RB20, RB25 and RB26 series engines.
95_240
Posts: 560
Joined: Fri Jan 07, 2005 4:26 pm
Car: 1995 240sx

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I have a series 2 rb25 with greddy manifold, q45 throttle body, and I'm running 10 psi. I hooked it up to a consult program and when it is running ok the idle is at 1400 rpms, maf voltage is about 1.5, tps is .45, injection time is 2.5 ms, and my vacuum is at 20Hg. The afr reading fluctuates from 14.5 to 15.5. After i rev the engine a few times the afrs read 10. The idle fluctuates between 500-800, the maf reads 2.5 volts, tps remains the same, and the injection time jumps up to 7.5 ms. The vacuum also drops to 10Hg. The timing increases to about 35 BTDC when I rev the engine and when it drops back to idle the reading is between 5-10 BTDC. I've unplugged individual sensors and the only one that did anything was the maf. When it was unplugged the car would stall. Any help is appreciated.


95_240
Posts: 560
Joined: Fri Jan 07, 2005 4:26 pm
Car: 1995 240sx

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So i guess my car is pulling timing for some reason. I tested the knock sensors according to the fsm and the voltage at the ecu is zero on both. I hooked up a 1M ohm 1/4 watt resistor to trick the ecu and still no voltage. Does the ecu actually supply voltage to the knock sensors and my ecu is fried or am I doing something wrong? There is continuity between the sensor plug and ecu so the wiring is fine.

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Carl H
Posts: 5985
Joined: Mon Aug 04, 2003 4:09 am
Car: 1995 Nissan 240SX SE RB30DET

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ecu does not provide voltage to the knock sensors...it is a resistance change based on knock.
problem right off the bat is the maf, idle voltage should be in the 1.2-1.4v range.

95_240
Posts: 560
Joined: Fri Jan 07, 2005 4:26 pm
Car: 1995 240sx

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Yeah I didn't think there was supposed to be voltage at the knock sensor. I guess it is just another screwup in the fsm. I have tried a couple of different mafs and one was known to be good. The thing with the maf is it is between 1.2-1.4 at idle but after I rev the engine is when everything gets jacked up. The idle drops and you can actually hear more air being pulled through the maf. This is exactly when the vacuum drops as well. I have set the timing but something is causing the car to go into limp mode and pulling timing and dumping fuel.


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