RB25det once at op. temp stumbles then dies - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

raiden571 · 03-30-2013, 09:18 PM

the car is a 300zx with an rb25 in it running AEM.
what is happening:
when the car is cold or has been sitting for a while it starts and idles fine. can rev it up, drive around the block, etc. no check engine lights, everything else in car works perfectly fine. as it reaches operating temp or runs for a while it will start to stumble then die.
i disconnected the cas tapped it with a rubber mallet as few times and reinstalled. car started, ran great for about 10mins. turned it off. worked in the garage for a little while and when i started it again, started stumbling then dies you can barely keep it running if you feather the throttle just right. if you dont touch the throttle you can turn it over and will run for under 2seconds and instantly die. still no CELS.
my intuition is to change the CAS but could there be something else?
the car is also using the AEM MAF sensor which is fairly new so i dont think thats it. brand new fuel pump, tried swapping coils around to see if it affected anything, it didnt and the ignitor on it is slightly newer.

pretty frustrated at this point and dont want to just start throwing money at the problem

Kingtal0n · 03-30-2013, 10:30 PM

sounds like it just needs tuning. theres adjustments for temperature vs fuel, it sounds like the coolant temp correction is pulling too much fuel for the operating temp.

raiden571 · 03-31-2013, 06:27 AM

The car has run on AEM for the passed two years on the same map without tweaking. From 90deg days in the summer to the dead of winter when i would start it move around the garage and let it warm up. I dont think its in the tune. My A/F is spot on when running properly.
guess i should have mentioned the car has been this way for a while and never had problems until recently

Boostoff · 03-31-2013, 07:09 AM

Are you running 2 loops (open and closed) for cold start cycle and normal op? I would still at least review the tune if you can. It could also be an IACV problem, how do you clean the intake if at all? Some products if sprayed into the intake runners via the TB can screw up the IACV pretty bad. Spray the electrical connectors with elec conn spray, and double check the vaccum lines and connections.

raiden571 · 03-31-2013, 07:44 AM

checked all the vacuum lines, ignition and sensor connections. If it was an IACV issue it would have an irratic idle, which it doesnt. one odd thing tho i noticed is that when its cold and started, it will temporarily miss on cyl 1. unplugged coil packs one by one to confirm on this cyl. but, if you crack the throttle a few times it clears up. its intermittent that's why i don't think its a mechanical issue such as a vacuum leak or something like that. i was thinking maybe run the car until it spits and sputters then unbolt the CAS and spin it by hand.

figured everyone likes pictures

OutToWinPAHC · 03-31-2013, 08:18 AM

Running AEM but no CEL because it does not generate CEL, Best thing is to hook up the computer and view the sensor readings and CAS tacking in AEM to see if it's doing something strange. I assume your using the AEM CAS trigger wheel?

raiden571 · 03-31-2013, 08:25 AM

using the oem sensor. ill have to get the AEM software on my laptop since it was tuned by SloMotion a while back
EDIT: actually ill have to check, i havent had the cas apart and it was never mentioned by the tuner

Kingtal0n · 03-31-2013, 09:04 AM

whoa take it easy. one simple thing first, then once you eliminate all the simple easy things THEN Start taking stuff apart.

Use the aem software to check all the sensors first. make sure nothing is out of the ordinary. The aem software will pretty much tell you (if you know how to examine it) what the problem is. You might need to save the base map, and start playing with the numbers to find out, though.

for Example:
WHen the problem occurs, start adding global fuel to the map (either via coolant global, or simply select the entire map and add fuel) to see if the problem is even fuel related.

#2 be specific, what OXygen sensor(s) are you running? A NARROWBAND? A WIDEBAND? BOTH? WHERE ARE THEY INSTALLED? HOW FAR FROM THE TURBO?

raiden571 · 03-31-2013, 10:22 AM

AEM wideband and its roughly 15-20inches away. i need to stress that the car ran great for 2yrs and i have never changed anything except the oil, plugs, just basic maintenance.
and it also has the OEM o2 sensor that is about. Im going to put AEM on my laptop and try it out this evening but i have only messed with CROME on Honda/Acura. Ive never had a problem like this before with my other vehicles.
all the research i have done has pointed to coolant temp sensor, CAS, and MAF. the coolant temp sensor is quite new and i dont see how it could drastically affect the operation of the car because what i have witnessed when tuning is that no matter how much you throw off the coolant temp intentionally, it only adjusted the fuel map by a few % across the board. unless im really missing something, the OE MAF was replaced with AEM MAP and IAT sensors. The CAS i could see affecting it in this manner.
butat this point im ready to try anything. but like i said, when the car has ran great for this long on this map with out issue and now it starts acting like this, it just leads me to think its sensor related

gtrmonkey · 03-31-2013, 12:14 PM

did you check the VTEC solenoid?

raiden571 · 03-31-2013, 12:18 PM

Quote:

Originally Posted by gtrmonkey

did you check the VTEC solenoid?

I'll smack you

inopsey · 03-31-2013, 01:26 PM

have you checked your compression? you mentioned when cold is seems to miss on cyl 1. wont hurt to check compression

raiden571 · 03-31-2013, 02:13 PM

The car isn't smoking, plugs are clean, no crossing of fluids. I can't see how it could be low

inopsey · 03-31-2013, 02:29 PM

it will confirm that the head/engine are in good condition. wont hurt to do, cheap easy and quick; you find out some good info about your engine regardless

raiden571 · 03-31-2013, 03:14 PM

I agree completely with that, but it won't help me narrow down where the problem is coming from

raiden571 · 04-08-2013, 12:32 PM

Update: replaced ignitor, replaced plugs, checked coilpacks for cracks (none) and cleaned out connections and problem still exists. I have a new coolant temp sensor to install tonight and see if it changes anything. Won't be able to get it hooked up to a laptop until the weekend. Car has me seriously pissed off.
And it has no MAF sensor so I'm assuming its running off of the AEM MAP and IAT sensors.

03-30-2013, 09:18 PM	#1
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	RB25det once at op. temp stumbles then dies the car is a 300zx with an rb25 in it running AEM. what is happening: when the car is cold or has been sitting for a while it starts and idles fine. can rev it up, drive around the block, etc. no check engine lights, everything else in car works perfectly fine. as it reaches operating temp or runs for a while it will start to stumble then die. i disconnected the cas tapped it with a rubber mallet as few times and reinstalled. car started, ran great for about 10mins. turned it off. worked in the garage for a little while and when i started it again, started stumbling then dies you can barely keep it running if you feather the throttle just right. if you dont touch the throttle you can turn it over and will run for under 2seconds and instantly die. still no CELS. my intuition is to change the CAS but could there be something else? the car is also using the AEM MAF sensor which is fairly new so i dont think thats it. brand new fuel pump, tried swapping coils around to see if it affected anything, it didnt and the ignitor on it is slightly newer. pretty frustrated at this point and dont want to just start throwing money at the problem

03-31-2013, 09:04 AM	#8
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	whoa take it easy. one simple thing first, then once you eliminate all the simple easy things THEN Start taking stuff apart. Use the aem software to check all the sensors first. make sure nothing is out of the ordinary. The aem software will pretty much tell you (if you know how to examine it) what the problem is. You might need to save the base map, and start playing with the numbers to find out, though. for Example: WHen the problem occurs, start adding global fuel to the map (either via coolant global, or simply select the entire map and add fuel) to see if the problem is even fuel related. #2 be specific, what OXygen sensor(s) are you running? A NARROWBAND? A WIDEBAND? BOTH? WHERE ARE THEY INSTALLED? HOW FAR FROM THE TURBO? __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

03-30-2013, 10:30 PM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	sounds like it just needs tuning. theres adjustments for temperature vs fuel, it sounds like the coolant temp correction is pulling too much fuel for the operating temp. __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

03-31-2013, 06:27 AM	#3
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	The car has run on AEM for the passed two years on the same map without tweaking. From 90deg days in the summer to the dead of winter when i would start it move around the garage and let it warm up. I dont think its in the tune. My A/F is spot on when running properly. guess i should have mentioned the car has been this way for a while and never had problems until recently

03-31-2013, 07:09 AM	#4
Boostoff Zilvia Member Join Date: Aug 2007 Location: Germantown Posts: 178 Trader Rating: (1) Feedback Score: 1 reviews	Are you running 2 loops (open and closed) for cold start cycle and normal op? I would still at least review the tune if you can. It could also be an IACV problem, how do you clean the intake if at all? Some products if sprayed into the intake runners via the TB can screw up the IACV pretty bad. Spray the electrical connectors with elec conn spray, and double check the vaccum lines and connections.

03-31-2013, 07:44 AM	#5
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	checked all the vacuum lines, ignition and sensor connections. If it was an IACV issue it would have an irratic idle, which it doesnt. one odd thing tho i noticed is that when its cold and started, it will temporarily miss on cyl 1. unplugged coil packs one by one to confirm on this cyl. but, if you crack the throttle a few times it clears up. its intermittent that's why i don't think its a mechanical issue such as a vacuum leak or something like that. i was thinking maybe run the car until it spits and sputters then unbolt the CAS and spin it by hand. figured everyone likes pictures

03-31-2013, 08:18 AM	#6
OutToWinPAHC Zilvia Addict Join Date: May 2007 Location: Florida Posts: 746 Trader Rating: (6) Feedback Score: 6 reviews	Running AEM but no CEL because it does not generate CEL, Best thing is to hook up the computer and view the sensor readings and CAS tacking in AEM to see if it's doing something strange. I assume your using the AEM CAS trigger wheel?

03-31-2013, 08:25 AM	#7
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	using the oem sensor. ill have to get the AEM software on my laptop since it was tuned by SloMotion a while back EDIT: actually ill have to check, i havent had the cas apart and it was never mentioned by the tuner

03-31-2013, 10:22 AM	#9
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	AEM wideband and its roughly 15-20inches away. i need to stress that the car ran great for 2yrs and i have never changed anything except the oil, plugs, just basic maintenance. and it also has the OEM o2 sensor that is about. Im going to put AEM on my laptop and try it out this evening but i have only messed with CROME on Honda/Acura. Ive never had a problem like this before with my other vehicles. all the research i have done has pointed to coolant temp sensor, CAS, and MAF. the coolant temp sensor is quite new and i dont see how it could drastically affect the operation of the car because what i have witnessed when tuning is that no matter how much you throw off the coolant temp intentionally, it only adjusted the fuel map by a few % across the board. unless im really missing something, the OE MAF was replaced with AEM MAP and IAT sensors. The CAS i could see affecting it in this manner. butat this point im ready to try anything. but like i said, when the car has ran great for this long on this map with out issue and now it starts acting like this, it just leads me to think its sensor related

03-31-2013, 12:14 PM	#10
gtrmonkey Leaky Injector Join Date: May 2004 Location: ATL Posts: 113 Trader Rating: (0) Feedback Score: 0 reviews	did you check the VTEC solenoid?

03-31-2013, 01:26 PM	#12
inopsey Nissanaholic! Join Date: Jul 2008 Location: canada Posts: 1,701 Trader Rating: (21) Feedback Score: 21 reviews	have you checked your compression? you mentioned when cold is seems to miss on cyl 1. wont hurt to check compression

03-31-2013, 02:13 PM	#13
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	The car isn't smoking, plugs are clean, no crossing of fluids. I can't see how it could be low

03-31-2013, 02:29 PM	#14
inopsey Nissanaholic! Join Date: Jul 2008 Location: canada Posts: 1,701 Trader Rating: (21) Feedback Score: 21 reviews	it will confirm that the head/engine are in good condition. wont hurt to do, cheap easy and quick; you find out some good info about your engine regardless

03-31-2013, 03:14 PM	#15
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	I agree completely with that, but it won't help me narrow down where the problem is coming from

04-08-2013, 12:32 PM	#16
raiden571 Join Date: Mar 2013 Location: ohio Age: 36 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	Update: replaced ignitor, replaced plugs, checked coilpacks for cracks (none) and cleaned out connections and problem still exists. I have a new coolant temp sensor to install tonight and see if it changes anything. Won't be able to get it hooked up to a laptop until the weekend. Car has me seriously pissed off. And it has no MAF sensor so I'm assuming its running off of the AEM MAP and IAT sensors.