Weird richness problem along with rough idle when cold started - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

sd8ted · 04-27-2013, 04:56 PM

Ok guys,

My setup:
Redtop SR20DET 9.0:1 CR 86.5mm pistons, GT2871R .86, SARD 850cc, Splitfire Ignition, HKS 272 cams, all bolt-ons. Tuned with Nistune.

Had the cams and ignition installed and car re-tuned a few weeks ago. Made 411hp 386tq spiking to 19ish psi and holding around 17ish, previously was making 354hp 338tq. Car is a little on the rich side, idles around mid to high 12's and cruising is in the 13's, low 14's when its decently warm.

Problem #1:
When the car is cold started, it doesn't like to stay alive without some throttle for the first minute or so. It will sputter and show 10 AFR's with partial throttle at around 1500-2000rpms, it will fully rev fine, and sometimes u can hear some compressor surge when holding the rpms in that range. This only happens until the car gets up to temp then it idles fine. Gonna take the IIAC off and clean it soon, maybe that will help some.

Problem #2:
For this first few minutes of driving, the wide-band shows 10.0-10.5. Then it will slowly climb up to 13's. I can drive around town with the car at normal operating temps and then go into the store and come back, crank the car up, still at proper temps, and it will do the same thing. Starts out in the 10's and will slowly climb back up to 13's after a mile or 2 of driving. Car feels heavy and restrained with to 1/2 or more throttle with wide-band reading 10.0 flat, dead rich until AFR's start reading right then smooths out.

Problem #3:
Cruising in any gear, if i give it WOT it will bog for a second and then pull hard. AFR's hits 10.0 then climbs up from there. Even occurs with a quick blimp of the throttle, shoots down to 10.0 and can feel a little bog.

I'm thinking maybe it could be the ECU? It has done this richness after start-up for while now(even when turning off, running into the store then cranking the car back up), but the bogging when cold started and hitting super rich with throttle started after the last install/tune. My mechanic/tuner hasn't dealt with this problem before.

Anyone ever have or heard of this problem? Car runs very smooth when cruising and idles fine when coming to a stop. Just baffling to me.

I can make a video of whats happening if needed.

04-27-2013, 04:56 PM	#1
sd8ted Leaky Injector Join Date: Nov 2005 Location: Greenville, SC Posts: 72 Trader Rating: (0) Feedback Score: 0 reviews	Weird richness problem along with rough idle when cold started Ok guys, My setup: Redtop SR20DET 9.0:1 CR 86.5mm pistons, GT2871R .86, SARD 850cc, Splitfire Ignition, HKS 272 cams, all bolt-ons. Tuned with Nistune. Had the cams and ignition installed and car re-tuned a few weeks ago. Made 411hp 386tq spiking to 19ish psi and holding around 17ish, previously was making 354hp 338tq. Car is a little on the rich side, idles around mid to high 12's and cruising is in the 13's, low 14's when its decently warm. Problem #1: When the car is cold started, it doesn't like to stay alive without some throttle for the first minute or so. It will sputter and show 10 AFR's with partial throttle at around 1500-2000rpms, it will fully rev fine, and sometimes u can hear some compressor surge when holding the rpms in that range. This only happens until the car gets up to temp then it idles fine. Gonna take the IIAC off and clean it soon, maybe that will help some. Problem #2: For this first few minutes of driving, the wide-band shows 10.0-10.5. Then it will slowly climb up to 13's. I can drive around town with the car at normal operating temps and then go into the store and come back, crank the car up, still at proper temps, and it will do the same thing. Starts out in the 10's and will slowly climb back up to 13's after a mile or 2 of driving. Car feels heavy and restrained with to 1/2 or more throttle with wide-band reading 10.0 flat, dead rich until AFR's start reading right then smooths out. Problem #3: Cruising in any gear, if i give it WOT it will bog for a second and then pull hard. AFR's hits 10.0 then climbs up from there. Even occurs with a quick blimp of the throttle, shoots down to 10.0 and can feel a little bog. I'm thinking maybe it could be the ECU? It has done this richness after start-up for while now(even when turning off, running into the store then cranking the car back up), but the bogging when cold started and hitting super rich with throttle started after the last install/tune. My mechanic/tuner hasn't dealt with this problem before. Anyone ever have or heard of this problem? Car runs very smooth when cruising and idles fine when coming to a stop. Just baffling to me. I can make a video of whats happening if needed.