Need help from Rb gurus (code 21) - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

singlecamslam · 08-10-2016, 09:15 PM

So my car is running like garbage, only once it warms up. I have nissan datascan and get a constant code 21, ignition circuit. This is a spec 2 rb25, i have ls1 coilpacks, not a single cylinder is misfiring, once the car warms up it looses power and shuts off randomly, and very hard to start back up.

Things i have done:
Checked coilpack wiring
Cleaned MAF
Changed sparkplugs
took my entire harness apart
Changed mafs once (to a used one)

The car will start up if i unplug the MAF, but in safe mode, i have 3 different mafs and it does the same shit, i doubt all 3 mafs are bad? Any suggestions will help, this thing is pissing me off.

dbeiler · 08-11-2016, 07:02 PM

Whenever an engine runs poorly or shuts only off after warming up (getting heat soaked), the primary suspect is the position sensor. A failing sensor will send erratic signals because it's affected by heat. The camshaft position sensor can be tested with a meter per the FSM. An easier method (and my personal favorite) is to run the engine up to operating temp until it starts misfiring, shut it off, remove the suspect camshaft position sensor, put it in the freezer for a few minutes to cool down, reinstall it onto the (still heat soaked) engine, and fire it up. If the engine runs normally with a cool sensor, you know the sensor is failing and it's time for a new one. These RB electronics are now 20 years old and failing left and right.

Isn't the code 21 commonly present with the LS coils? I had a code 21 (with Splifire setup) then eventually discovered I was missing a coilpack ground wire. Something to look at.

Yellow4g63 · 08-11-2016, 07:16 PM

Coolant temp sensor makes the car run like shyt too if it's bad. When mine went bad It didn't throw a code to the ecu.

singlecamslam · 08-12-2016, 03:09 PM

I haven't heard about a code 21 problem and ls coils, is this normal since the wiring gets changed a little? Can someone confirm. Also I made all new grounds for each coil pack, I will try the freezer idea for the cas, I changed my coolant sensor not too long ago. Keep the ideas coming I'll be trying everything.
The most frustrating part is that this problem is very erratic and not consistent at all, but what is consistent is the motor runs much better cold than warm, as it warms the performance detereorates fast

Yellow4g63 · 08-12-2016, 06:41 PM

Code 21 is because the factory ignitor is gone when you do the ls coil swap.

08-10-2016, 09:15 PM	#1
singlecamslam Post Whore! Join Date: Apr 2008 Location: Norcal Posts: 2,534 Trader Rating: (10) Feedback Score: 10 reviews	Need help from Rb gurus (code 21) So my car is running like garbage, only once it warms up. I have nissan datascan and get a constant code 21, ignition circuit. This is a spec 2 rb25, i have ls1 coilpacks, not a single cylinder is misfiring, once the car warms up it looses power and shuts off randomly, and very hard to start back up. Things i have done: Checked coilpack wiring Cleaned MAF Changed sparkplugs took my entire harness apart Changed mafs once (to a used one) The car will start up if i unplug the MAF, but in safe mode, i have 3 different mafs and it does the same shit, i doubt all 3 mafs are bad? Any suggestions will help, this thing is pissing me off. __________________ Nothing says racecar like a stock car with no interior.

08-11-2016, 07:16 PM	#3
Yellow4g63 Zilvia FREAK! Join Date: Jan 2003 Location: Socal Posts: 1,454 Trader Rating: (5) Feedback Score: 5 reviews	Coolant temp sensor makes the car run like shyt too if it's bad. When mine went bad It didn't throw a code to the ecu. __________________ 95 240sx RB20 415whp 91 Nx2000 VVL yo

08-12-2016, 03:09 PM	#4
singlecamslam Post Whore! Join Date: Apr 2008 Location: Norcal Posts: 2,534 Trader Rating: (10) Feedback Score: 10 reviews	I haven't heard about a code 21 problem and ls coils, is this normal since the wiring gets changed a little? Can someone confirm. Also I made all new grounds for each coil pack, I will try the freezer idea for the cas, I changed my coolant sensor not too long ago. Keep the ideas coming I'll be trying everything. The most frustrating part is that this problem is very erratic and not consistent at all, but what is consistent is the motor runs much better cold than warm, as it warms the performance detereorates fast __________________ Nothing says racecar like a stock car with no interior. Last edited by singlecamslam; 08-12-2016 at 04:54 PM..

08-12-2016, 06:41 PM	#5
Yellow4g63 Zilvia FREAK! Join Date: Jan 2003 Location: Socal Posts: 1,454 Trader Rating: (5) Feedback Score: 5 reviews	Code 21 is because the factory ignitor is gone when you do the ls coil swap. __________________ 95 240sx RB20 415whp 91 Nx2000 VVL yo

08-11-2016, 07:02 PM	#2
dbeiler Zilvia Junkie Join Date: Jun 2012 Location: Lancaster county, PA Age: 34 Posts: 465 Trader Rating: (4) Feedback Score: 4 reviews	Whenever an engine runs poorly or shuts only off after warming up (getting heat soaked), the primary suspect is the position sensor. A failing sensor will send erratic signals because it's affected by heat. The camshaft position sensor can be tested with a meter per the FSM. An easier method (and my personal favorite) is to run the engine up to operating temp until it starts misfiring, shut it off, remove the suspect camshaft position sensor, put it in the freezer for a few minutes to cool down, reinstall it onto the (still heat soaked) engine, and fire it up. If the engine runs normally with a cool sensor, you know the sensor is failing and it's time for a new one. These RB electronics are now 20 years old and failing left and right. Isn't the code 21 commonly present with the LS coils? I had a code 21 (with Splifire setup) then eventually discovered I was missing a coilpack ground wire. Something to look at.