So you think you know engines eh?.... - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Ryan.maccie · 10-26-2012, 01:09 AM

Alright, So here is the sitch, Its got me at my witt's end..

Lovely young lady buys a mint s13 hatch, 106xxx km, lady driven, one owner *grandma* auto.. By far one of the minty'st cars I have seen in ages..

We take it through emissions testing, and it fails horribly in the idle portion..

Readings are as follows:
DRIVING
HC
Max:90.00
Vehicle 8.00

CO
Max: .76
Vehicle: 0.00

NOx
Max: 1117
Vehicle: 12.00

IDLE

HC
Max:108
Vehicle:276

CO:
Max: .82
Vehicle: 4.43

So, With that information I decided to look at the coolant temp sensor as the culprate, Backed that up with a satanic code 13 off the ECU.. I replaced the sensor, Code was still apparent. I than tried another brand new sensor, Code still remained.
So I checked continuity between the 3 ecu pins, and the 2 sensor pins and confirmed continuity.. Still the code was coming back. So I rewired the Blue/Orange I believe from the CTS-> pin 18(i believe), At wich point the CTS code dissappeared.. So I swapped the cat for a brand new one I had laying around along with a brand new 02 sensor.

Car failed again same readings same situation.. CTS code came back..

At this point I than played peek-aboo with code 13 for a couple days.. I have now ran the ground wire for the CTS straight to the block wich seems to have delt with that issue, For the time being..

I am now showing Code 55.

Although with code 55 being shown, the afr's measured at the tail pipe via an AEM UEGO at idle are still 12.2-13.6..

Timing is set to 15*
CTS Resistance is correct
Maf Voltage at idle is 1.44
Fuel pressure vac disconnected is ~40psi
Tps is set to .45

What am I missing that would cause the idle circut to be pig rich as it is..
I think this is something stupid and small, that I am just not thinking of..

I feel like I have tried everything at this point.. The car runs like a swiss watch, doesnt miss a beat.. But is stupid rich..

Things I think are possible at this point..

Leaky injector
Exhaust leak at manifold giving o2 sensor a false lean.

Discuss please!

Twinkies! · 10-26-2012, 01:36 AM

Could it be the ecu? Mine wouldn't pass smog so my neighbor gave me his bad bam! It worked

steve shadows · 10-26-2012, 01:39 PM

What condition is the CAT in? A lot of times they are blown out or jacked up even after 100K miles on USDM KA 240s...

godsmack · 10-26-2012, 03:57 PM

I'm gonna go with the leaky injector.

Kingtal0n · 10-27-2012, 06:28 PM

lol, air fuel is adjusted in closed-loop by the narrowband oxygen sensor. Install a narrowband oxygen sensor and let the ECU do it's job.

Or, plan B is use the analog output from the AEM to simulate a narrowband.

Either way, the ECU is capable of using that 0-1V input to modify injector pulse width.

hooknbook240sx · 11-01-2012, 09:47 PM

As previously mentioned I would look into the catalytic converter being bad or clogged. replace the oxygen sensor and make sure its functioning properly if that is bad its giving a false code the ecu.

10-26-2012, 01:09 AM	#1
Ryan.maccie Leaky Injector Join Date: Nov 2007 Location: Richmond Posts: 58 Trader Rating: (0) Feedback Score: 0 reviews	So you think you know engines eh?.... Alright, So here is the sitch, Its got me at my witt's end.. Lovely young lady buys a mint s13 hatch, 106xxx km, lady driven, one owner grandma auto.. By far one of the minty'st cars I have seen in ages.. We take it through emissions testing, and it fails horribly in the idle portion.. Readings are as follows: DRIVING HC Max:90.00 Vehicle 8.00 CO Max: .76 Vehicle: 0.00 NOx Max: 1117 Vehicle: 12.00 IDLE HC Max:108 Vehicle:276 CO: Max: .82 Vehicle: 4.43 So, With that information I decided to look at the coolant temp sensor as the culprate, Backed that up with a satanic code 13 off the ECU.. I replaced the sensor, Code was still apparent. I than tried another brand new sensor, Code still remained. So I checked continuity between the 3 ecu pins, and the 2 sensor pins and confirmed continuity.. Still the code was coming back. So I rewired the Blue/Orange I believe from the CTS-> pin 18(i believe), At wich point the CTS code dissappeared.. So I swapped the cat for a brand new one I had laying around along with a brand new 02 sensor. Car failed again same readings same situation.. CTS code came back.. At this point I than played peek-aboo with code 13 for a couple days.. I have now ran the ground wire for the CTS straight to the block wich seems to have delt with that issue, For the time being.. I am now showing Code 55. Although with code 55 being shown, the afr's measured at the tail pipe via an AEM UEGO at idle are still 12.2-13.6.. Timing is set to 15* CTS Resistance is correct Maf Voltage at idle is 1.44 Fuel pressure vac disconnected is ~40psi Tps is set to .45 What am I missing that would cause the idle circut to be pig rich as it is.. I think this is something stupid and small, that I am just not thinking of.. I feel like I have tried everything at this point.. The car runs like a swiss watch, doesnt miss a beat.. But is stupid rich.. Things I think are possible at this point.. Leaky injector Exhaust leak at manifold giving o2 sensor a false lean. Discuss please!

10-26-2012, 01:39 PM	#3
steve shadows Post Whore! Join Date: Aug 2003 Location: LA and OC Posts: 8,202 Trader Rating: (5) Feedback Score: 5 reviews	What condition is the CAT in? A lot of times they are blown out or jacked up even after 100K miles on USDM KA 240s... __________________ Like Me on FaceBook !

10-27-2012, 06:28 PM	#5
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	lol, air fuel is adjusted in closed-loop by the narrowband oxygen sensor. Install a narrowband oxygen sensor and let the ECU do it's job. Or, plan B is use the analog output from the AEM to simulate a narrowband. Either way, the ECU is capable of using that 0-1V input to modify injector pulse width. __________________ 5.3/4l80e/turbo 240sx playthrough: https://tinyurl.com/turbo240

Thread Tools
Show Printable Version Email this Page
Display Modes
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode

10-26-2012, 01:36 AM	#2
Twinkies! Zilvia Junkie Join Date: Apr 2012 Location: Rosamond California Posts: 546 Trader Rating: (2) Feedback Score: 2 reviews	Could it be the ecu? Mine wouldn't pass smog so my neighbor gave me his bad bam! It worked

10-26-2012, 03:57 PM	#4
godsmack Zilvia Addict Join Date: Feb 2009 Location: Allentown, PA Age: 36 Posts: 652 Trader Rating: (0) Feedback Score: 0 reviews	I'm gonna go with the leaky injector.

11-01-2012, 09:47 PM	#6
hooknbook240sx Join Date: May 2011 Location: South Florida Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	As previously mentioned I would look into the catalytic converter being bad or clogged. replace the oxygen sensor and make sure its functioning properly if that is bad its giving a false code the ecu.