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

Go Back   Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum > General > Tech Talk

Tech Talk Technical Discussion About The Nissan 240SX and Nissan Z Cars


Reply
 
Thread Tools Display Modes
Old 08-24-2011, 09:26 PM   #1
Infamax
Zilvia Member
 
Infamax's Avatar
 
Join Date: Apr 2005
Location: Yuba City (Nor Cal)
Age: 28
Posts: 223
Trader Rating: (7)
Feedback Score: 7 reviews
Failed Smog, high HC at idle

I've searched and tried various things. I've changed spark plugs, O2 sensor, CTS, vacuum lines, cleaned the maf, new air filter, changed cap and rotor, checked timing and set idle multiple times, and I still haven't been able to pass the sniffer.

The HC and CO are high at idle. Once the rpms starting going up, the smog numbers go down. As soon as the smog tech lets off the throttle and the motor gets to idle speed, the HC start shooting up. The numbers are fine anytime besides right at idle.

I'm at a lose, any help would be appreciated. I've included a pic of my smog sheet.
Attached Images
File Type: jpg IMG_0171.jpg (248.0 KB, 51 views)
Infamax is offline   Reply With Quote
Sponsored Links
Old 08-24-2011, 09:44 PM   #2
nismolvr
Zilvia Junkie
 
nismolvr's Avatar
 
Join Date: Aug 2006
Location: Modesto,California
Posts: 357
Trader Rating: (3)
Feedback Score: 3 reviews
s13

has any one messed with throttle screw settings? Have you cleaned Throttle valve of any gunk or carbon deposits ?maybe certain air passages in TB are clogged and your engine starves for air at idle, runs rich. New air filter? High HCs with High COs at idle are a sign of not enough air . Will bet some one messed with throttle screw settings....Hope this helps..
__________________
nismolvr is offline   Reply With Quote
Old 08-24-2011, 10:08 PM   #3
Infamax
Zilvia Member
 
Infamax's Avatar
 
Join Date: Apr 2005
Location: Yuba City (Nor Cal)
Age: 28
Posts: 223
Trader Rating: (7)
Feedback Score: 7 reviews
It's a SOHC engine BTW.

I'm not sure I know where the throttle screw is located. I've owned the car for 5 years, and it's had the same SOHC since last time I smogged, which passed just fine. I pretty sure the throttle screw hasn't been messed with.

I'll pull and cleaning out the throttle body and see if that helps any.

Last edited by Infamax; 08-24-2011 at 11:03 PM..
Infamax is offline   Reply With Quote
Old 08-24-2011, 10:55 PM   #4
qoOp
Zilvia Member
 
qoOp's Avatar
 
Join Date: Aug 2011
Location: San Diego, CA
Age: 27
Posts: 162
Trader Rating: (8)
Feedback Score: 8 reviews
Send a message via AIM to qoOp
ah, CA smog sucks! i'm still trying to get my car to pass. >.>
qoOp is offline   Reply With Quote
Old 08-25-2011, 03:41 AM   #5
Wookie384
Premium Member
 
Wookie384's Avatar
 
Join Date: May 2007
Location: N. Hollywood / Burbank
Age: 29
Posts: 627
Trader Rating: (7)
Feedback Score: 7 reviews
Send a message via AIM to Wookie384
Check EGR. It's probably clogged.
Wookie384 is offline   Reply With Quote
Old 08-25-2011, 05:18 AM   #6
mnmax
Zilvia Member
 
mnmax's Avatar
 
Join Date: Nov 2007
Location: in the Marines now... upstate NY
Age: 30
Posts: 194
Trader Rating: (0)
Feedback Score: 0 reviews
Quote:
Originally Posted by Wookie384 View Post
Check EGR. It's probably clogged.
^^Yes definitely, check your EGR. With it clogged, you're not getting the right (or any) recirculation of unburnt HC and CO back into your combustion chamber.

I used to be a smog tech back in the day and it always sucked that CA law prohibited us from explaining what might be the possible issue with their car when it doesn't pass and customers would come back in saying that they had spent up to thousands of $ trying to rectify the problem.
__________________
GIGGITY GIGGITY GIGGITY GOOOO!!!!

Last edited by mnmax; 08-25-2011 at 05:19 AM.. Reason: fixed bad punctuation...
mnmax is offline   Reply With Quote
Old 08-25-2011, 05:43 AM   #7
mxexux
Zilvia Junkie
 
mxexux's Avatar
 
Join Date: Jun 2008
Location: SoCal 949
Posts: 353
Trader Rating: (8)
Feedback Score: 8 reviews
^^^ ya but how would a clogged EGR cause high HC's and CO? The numbers seem to say that it is running rich to the point of misfiring at idle.

OP, the pic shows that you failed visual on "other related emissions components." And also it says that the timing was "defective." Do you have any mods on the engine? What is the spark timing set at?
mxexux is offline   Reply With Quote
Old 08-25-2011, 06:53 AM   #8
mnmax
Zilvia Member
 
mnmax's Avatar
 
Join Date: Nov 2007
Location: in the Marines now... upstate NY
Age: 30
Posts: 194
Trader Rating: (0)
Feedback Score: 0 reviews
Quote:
Originally Posted by mxexux View Post
^^^ ya but how would a clogged EGR cause high HC's and CO? The numbers seem to say that it is running rich to the point of misfiring at idle.
The amount of HC and CO exiting out the exhaust is basically regulated by the EGR either before or within the catalytic converter to be routed back into the engine to be burned. Whatever is left over is supposed to be trapped in the cat. If either of those fail, then the result will be too much emissions exiting the exhaust. So, it could be a couple of reasons:
1) clogged EGR valve or recirculatiion tube
2)catalytic converter failure
3)EGR valve not recieving signal or vacuum(depending on what type of EGR)
4)faulty EGR valve

Any of those could be the reason. Since you said that he also failed a visual inspect, it may be that his EGR may have been unplugged for whatever reason.

EDIT: Nevermind on that last statement. Just looked at the sheet, it says that EGR passed functional test
__________________
GIGGITY GIGGITY GIGGITY GOOOO!!!!

Last edited by mnmax; 08-25-2011 at 06:59 AM.. Reason: added
mnmax is offline   Reply With Quote
Old 08-25-2011, 01:44 PM   #9
Infamax
Zilvia Member
 
Infamax's Avatar
 
Join Date: Apr 2005
Location: Yuba City (Nor Cal)
Age: 28
Posts: 223
Trader Rating: (7)
Feedback Score: 7 reviews
I tried removing the egr pipe, It was rusted on and I couldn't break it loose. I'm gonna try again in the evening after it cools down and I get back from class. I'll give the egr valve and throttle body a good clean.

The smog tech had checked the egr solenoid, and said it appeared to be working properly. He also checked the egr valve and said it seemed to be working like it should.

The reason it said I failed visual was because the smog tech thought my timing was off. He thought the timing mark furthest to the left was 0* BTDC, when it's actually the second from the left. After that test, I've been going to a different smog station.

Could my problem be a faulty injector? If so, is there a way to check the injectors? I had previously read of a way to check the injectors using the ecu's self-diagnostic system, but I couldn't find anything on that again.
Infamax is offline   Reply With Quote
Old 08-25-2011, 02:00 PM   #10
mnmax
Zilvia Member
 
mnmax's Avatar
 
Join Date: Nov 2007
Location: in the Marines now... upstate NY
Age: 30
Posts: 194
Trader Rating: (0)
Feedback Score: 0 reviews
should be able to just google the year, make, and model of your car with trouble code chart and it should give a break down on how to read the trouble from the little blinking led's that you see on your ecu. unless you know someone that has nistune or consult to read it on a computer direct from your diagnostic port.
__________________
GIGGITY GIGGITY GIGGITY GOOOO!!!!
mnmax is offline   Reply With Quote
Old 08-25-2011, 02:08 PM   #11
Infamax
Zilvia Member
 
Infamax's Avatar
 
Join Date: Apr 2005
Location: Yuba City (Nor Cal)
Age: 28
Posts: 223
Trader Rating: (7)
Feedback Score: 7 reviews
I don't have a CEL, I know how to check the codes.

One of the 5 modes in the diagnostic system is used to test the fuel mix ratios. I tried looking up the thread that described how to check for improper working injector using the ecu's diagnostic system.
Infamax is offline   Reply With Quote
Old 08-25-2011, 10:04 PM   #12
Ekin_s13
 
Join Date: Jan 2010
Location: San Diego
Posts: 35
Trader Rating: (0)
Feedback Score: 0 reviews
i don't know why people are telling you to check the erg when the test is two speed idle. if you look at your co2 is low and o2 is high that show your cat is not work at 100%. i think you should change the cat and o2 sensor.
Ekin_s13 is offline   Reply With Quote
Old 08-26-2011, 01:56 AM   #13
mxexux
Zilvia Junkie
 
mxexux's Avatar
 
Join Date: Jun 2008
Location: SoCal 949
Posts: 353
Trader Rating: (8)
Feedback Score: 8 reviews
Quote:
Originally Posted by mnmax View Post
The amount of HC and CO exiting out the exhaust is basically regulated by the EGR either before or within the catalytic converter to be routed back into the engine to be burned. Whatever is left over is supposed to be trapped in the cat. If either of those fail, then the result will be too much emissions exiting the exhaust.
I'm going to have to strongly disagree with you there about what the EGR does. You are partially right about it reciculating exhaust gasses back into the intake, but its purpose is NOT to burn left over HC's and CO...Its only purpose is to reduce NOx by lowering combustion temps when it dillutes the intake charge with inert exhaust gasses.

OP, leaky injector is a definite possibility. Or, like MNMAX said, the CAT is another possible cause. I would lean more towards the injector though since the numbers show that the HC's are way too high, higher than the CAT is supposed to filter out any way.

Also, take a look at the vacuum lines that go to the fuel pressure regulator. If there is a vacuum leak there, the regulator may be leaving too much pressure in the rail at idle.
mxexux is offline   Reply With Quote
Old 08-26-2011, 07:20 AM   #14
nismolvr
Zilvia Junkie
 
nismolvr's Avatar
 
Join Date: Aug 2006
Location: Modesto,California
Posts: 357
Trader Rating: (3)
Feedback Score: 3 reviews
s13

This guys problem is only at idle ! EGR operates only off idle and cruise. If it was stuck closed he'd show high NOX@ 25 mph but its NoT!If it was opening slightly ,not seating correctly all the way @ idle it would misfire throwing your a/f ratios off . I bet it's just your idle air control valve Or throttle valve and not your EGR.
__________________
nismolvr is offline   Reply With Quote
Old 08-26-2011, 09:50 AM   #15
zerodameaon
Premium Member
 
zerodameaon's Avatar
 
Join Date: May 2009
Location: Bay Area CA, Sutherlin OR
Age: 26
Posts: 2,938
Trader Rating: (3)
Feedback Score: 3 reviews
Change your cat!! I had this exact issue almost the same numbers and i changed my cat to a Magnaflow 36306 i believe and i passed. Just barely but it passed. These idle tests are sadly harder to pass then the enhanced tests. My car would pass pretest enhanced but fail the regular test.
__________________
Quote:
Originally Posted by MrMigs View Post
That's a one-way trip to understeer land...
Quote:
Originally Posted by BKdaMoRoN View Post
Maybe you should petition the retards who are paying 5k for an S13.

Need to adjust your idle?
http://zilvia.net/f/s-chassis/395413...-pictures.html
zerodameaon is offline   Reply With Quote
Old 08-26-2011, 11:15 AM   #16
nismolvr
Zilvia Junkie
 
nismolvr's Avatar
 
Join Date: Aug 2006
Location: Modesto,California
Posts: 357
Trader Rating: (3)
Feedback Score: 3 reviews
Quote:
Originally Posted by zerodameaon View Post
Change your cat!! I had this exact issue almost the same numbers and i changed my cat to a Magnaflow 36306 i believe and i passed. Just barely but it passed. These idle tests are sadly harder to pass then the enhanced tests. My car would pass pretest enhanced but fail the regular test.
Now that I saw his o2 @ idle High O2 at Idle is Maybe a Vacuum leak causing a lean missfire Is Idle higher than normal RPMs?,If no Vacuum leak . I'd have to agree with this quote. Change the cat like the he advised.
__________________

Last edited by nismolvr; 08-26-2011 at 08:48 PM..
nismolvr is offline   Reply With Quote
Old 08-26-2011, 01:50 PM   #17
Wookie384
Premium Member
 
Wookie384's Avatar
 
Join Date: May 2007
Location: N. Hollywood / Burbank
Age: 29
Posts: 627
Trader Rating: (7)
Feedback Score: 7 reviews
Send a message via AIM to Wookie384
Cleaning out the EGR costs nothing but your time and brake clean, a cat, injectors, and/or O2 sensors cost money, start with the easiest cheapest shit before you throw your money into it. Even though EGR passes visual and functions, how are you sure the pipe itself isn't clogged/ restricted?

Sent from my HTC Aria using Tapatalk
Wookie384 is offline   Reply With Quote
Old 08-26-2011, 08:29 PM   #18
nismolvr
Zilvia Junkie
 
nismolvr's Avatar
 
Join Date: Aug 2006
Location: Modesto,California
Posts: 357
Trader Rating: (3)
Feedback Score: 3 reviews
Cool

Quote:
Originally Posted by Ekin_s13 View Post
i don't know why people are telling you to check the erg when the test is two speed idle. if you look at your co2 is low and o2 is high that show your cat is not work at 100%. i think you should change the cat and o2 sensor.
^^^^^^^ Exactly the guy failed in HC and Co @ idle!!!!!Why in the hell are people telling him to clean his EGR? High NOX readings are signs of bad EGR system ,period!EGR does not open @ idle !It only opens @ off idle and cruise not @ idle!!!! therefore stop telling the guy to clean his EGR.He failed @ idle people. !

Some of you sound like you know what your talking about but in reality dont know anything , look at his results Study them before you assume its an EGR problem! So much misinformation.
__________________
nismolvr is offline   Reply With Quote
Old 08-26-2011, 08:37 PM   #19
nismolvr
Zilvia Junkie
 
nismolvr's Avatar
 
Join Date: Aug 2006
Location: Modesto,California
Posts: 357
Trader Rating: (3)
Feedback Score: 3 reviews
Cool

Quote:
Originally Posted by Wookie384 View Post
Cleaning out the EGR costs nothing but your time and brake clean, a cat, injectors, and/or O2 sensors cost money, start with the easiest cheapest shit before you throw your money into it. Even though EGR passes visual and functions, how are you sure the pipe itself isn't clogged/ restricted?

Sent from my HTC Aria using Tapatalk
Dude the test results show its working!!!If he Had high NOX @ 15 MPH and @ 25 MPH it would show on his print out copy! Thats how you know the egr system is faulty. Here is a easier cheaper way of testing the EGR , Apply Vacuum directly to valve while engine is Idling .If it stalls and engine turns off , hello! it works.Sytem is unrestricted cause gases are getting by and his egr pipe isnt clogged.
Getting off way off subject , his problem is NOT EGR related.

people need to study how and when and why we have EGR systems in our vehicles .




The guy most likely has a vacuum leak causing a lean missfire , take carb cleaner and spray around intake and find your leak ,look for unplugged vacuum hoses.
__________________
nismolvr is offline   Reply With Quote
Old 08-29-2011, 12:19 PM   #20
LeaS13Zenki
Zilvia Addict
 
LeaS13Zenki's Avatar
 
Join Date: Aug 2010
Location: 562/323
Age: 21
Posts: 823
Trader Rating: (31)
Feedback Score: 31 reviews
yup somg alaways sucks same problem with my sohc i had vaccum leaks my car failed nasty.
__________________
AUTO REPAIRS, smogs ETCS ---> http://www.lea-autorepair.com/
LeaS13Zenki is offline   Reply With Quote
Reply

Bookmarks


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 07:43 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
vB.Sponsors
Copyright © 1998 - 2014, Zilvia.net™