RB25DET Idle Issues - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

encludemeout · 03-10-2012, 04:36 PM

Here is the background on my car. S13 with an S1 RB25DET swap.

Freddy Intake w/ Q45 throttle body
Z32 Fuel Filter
Walbro 255
FMIC
Full 3 Inch Exhaust
Stock Boost
Stock ECU
Stock MAF
Greddy Type S BOV, vented

Since I got my swap running, idle has always been an issue with it. On a cold start, it will sit anywhere from 1500-1600 rpm's. Then once warm drops down to anywhere from 800-1000 rpm's. That all seems normal. These are the issues I'm having with it.

-When rolling, if the car is put into neutral it will immediately jump up to around 500 rpms HIGHER than normal. So if it's still in cold start mode, it'll be around 2000 rpm, and if warmed up around 1300-1500 rpm. This will sit up around there until I come to a complete stop. Then as soon as I'm stopped, it drops to it's usual position.

-I can get almost no adjustment out of the idle screw. I did it the correct way, by letting the car warm up to operating temp, unplugging the tps sensor and adjusting the idle screw. Hardly any noticeable adjustment. Last time I check is was getting power too. I cleaned it out today and still not luck.

-Every now and then I'll get the classic Honda idle for a ~15 seconds. It goes up and down within around a 700 rpm range.

-If free rev'd above 4500 rpm's the motor wont be able to catch itself, and it dies. It will start right back up though.

-If you are rolling and punch it, the car will stutter initially and then go. Boost's fine and everything, it just seems as if it needs a split second to get it's shit together.

I'm about to buy a new IAC valve and see if it makes any difference. I currently have a three bolt valve, and need to find a replacement for it if anyone knows. Some say a 1.6L 91-94 Sentra will work, but after looking at pictures it doesn't look even remotely the same. Car runs really good besides all this. Anyone think IAC with me, or maybe a possible vacuum leak?

03-10-2012, 04:36 PM	#1
encludemeout Zilvia Member Join Date: Jul 2008 Location: Ohio Posts: 224 Trader Rating: (7) Feedback Score: 7 reviews	RB25DET Idle Issues Here is the background on my car. S13 with an S1 RB25DET swap. Freddy Intake w/ Q45 throttle body Z32 Fuel Filter Walbro 255 FMIC Full 3 Inch Exhaust Stock Boost Stock ECU Stock MAF Greddy Type S BOV, vented Since I got my swap running, idle has always been an issue with it. On a cold start, it will sit anywhere from 1500-1600 rpm's. Then once warm drops down to anywhere from 800-1000 rpm's. That all seems normal. These are the issues I'm having with it. -When rolling, if the car is put into neutral it will immediately jump up to around 500 rpms HIGHER than normal. So if it's still in cold start mode, it'll be around 2000 rpm, and if warmed up around 1300-1500 rpm. This will sit up around there until I come to a complete stop. Then as soon as I'm stopped, it drops to it's usual position. -I can get almost no adjustment out of the idle screw. I did it the correct way, by letting the car warm up to operating temp, unplugging the tps sensor and adjusting the idle screw. Hardly any noticeable adjustment. Last time I check is was getting power too. I cleaned it out today and still not luck. -Every now and then I'll get the classic Honda idle for a ~15 seconds. It goes up and down within around a 700 rpm range. -If free rev'd above 4500 rpm's the motor wont be able to catch itself, and it dies. It will start right back up though. -If you are rolling and punch it, the car will stutter initially and then go. Boost's fine and everything, it just seems as if it needs a split second to get it's shit together. I'm about to buy a new IAC valve and see if it makes any difference. I currently have a three bolt valve, and need to find a replacement for it if anyone knows. Some say a 1.6L 91-94 Sentra will work, but after looking at pictures it doesn't look even remotely the same. Car runs really good besides all this. Anyone think IAC with me, or maybe a possible vacuum leak?