Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 07-08-2004, 06:29 PM
Registered User
 
Join Date: Jul 2003
Posts: 555
failed NO emmissions test

Trying to figure out what causes to fail the NO (ppm) test on my kid's TOYOTA 1987 MR2

%CO 14.6 & 14.7
%O2 0.3 & 0.2
HC (ppm) 33 & 25
CO (%) 0.01 & 0.03
NO (ppm) 1115 & 735 max 825 & 764
failed the 15 mph test and barely passed the 25 mph test.

I also was told that the timing was of by 10 degrees, retarded I think but not positive.

Don't know what causes the NO emmisions, the cat was repalced two years ago, the car uses a quart of oil every 1k miles.

__________________
Thanks, Juan
Reply With Quote
  #2  
Old 07-08-2004, 06:37 PM
Registered User
 
Join Date: May 2002
Posts: 105
Check to make sure the EGR system is working. My guess would be a leaking EGR vavle.
Reply With Quote
  #3  
Old 07-08-2004, 06:43 PM
Registered User
 
Join Date: Jul 2003
Posts: 555
I'll check that, anything else???
__________________
Thanks, Juan
Reply With Quote
  #4  
Old 07-08-2004, 07:58 PM
Registered User
 
Join Date: Jul 2000
Posts: 638
failed NOx emission test

The oil consumption has probably killed the catalyst. The phosphorus in the oil (antiwear additive) is a permanent poison. 1qt/1000 miles is a LOT of oil consumption for that small engine.

You MIGHT try a high speed/high load 'burn-off' attempt on the catalyst before changing it. Also be sure the timing is right on, the EGR valve, plumbing, and passages are clean and working properly.
Reply With Quote
  #5  
Old 07-08-2004, 07:59 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: Eastern TN
Posts: 20,841
High NOx readings mean combustion temps are too high. EGR reduces combustion temps so start with that. If the spark timing was 10-degrees too advanced that might contribute to high combustion temps as well.

The folks at www.club4ag.com might have specific information.

Sixto
95 S420
87 300SDL
Reply With Quote
  #6  
Old 07-08-2004, 08:16 PM
Registered User
 
Join Date: Jul 2003
Posts: 555
Thanks for your replies, what do you mean by high speed high load burn off? 1 hour drive or longer?

The cat was replaced 2 years ago but I see what you mean.

I will take apart the EGR system and inspect it well.
__________________
Thanks, Juan
Reply With Quote
  #7  
Old 07-08-2004, 10:04 PM
Registered User
 
Join Date: Mar 2003
Location: Southern California
Posts: 2,249
If the engine has EGR check the valve function and control system.

Also, properly check and understand what the timing is relative to spec. You may have to short a couple of leads on the diagnostic connector to get a true initial timing value. Look on the emission control decal or get a shop manual. The timing is supposed to be measured as part of the test and recorded on the report.

Retarding the timing will reduce NOx since it reduces peak combustion temperature, and the CA inspection places no limit on how much the timing can be retarded from OE spec.

I doubt if there is anything wrong with the catalyst given the low HC and very low CO.

Duke
Reply With Quote
  #8  
Old 07-09-2004, 12:25 AM
Registered User
 
Join Date: Sep 2003
Location: S.F. Bayarea
Posts: 196
running lean

%CO2 14.6 & 14.7
%O2 0.3 & 0.2
HC (ppm) 33 & 25
CO (%) 0.01 & 0.03
NO (ppm) 1115 & 735 max 825 & 764

CO2 is relatively low comparing to a very good engine, EFFICIENT AND COMPLETE COMBUSTION (15.2 TO MAX 15.6).

O2 is high and CO is very low indicates lean mixture. Low CO may also leads to low catalyst converter efficiency. Air leak past the air metering stage?
__________________
Shane83SD
Reply With Quote
  #9  
Old 07-09-2004, 01:49 AM
Registered User
 
Join Date: Jul 2003
Posts: 555
great information, thank's.
Now what to do about it?
__________________
Thanks, Juan
Reply With Quote
  #10  
Old 07-09-2004, 03:37 AM
Registered User
 
Join Date: Sep 2003
Location: S.F. Bayarea
Posts: 196
Check the spark plug. If the insulator is white and/or blistering (normal is light tan), the engine is running lean and hot.

Possibilities:
Air duct leaking from air metering device to the intake manifold.
Leaking intake manifold gasket.
Throttle plate shaft leaking (loose).
etc., etc

Search the archive for leak detection techniques.
__________________
Shane83SD
Reply With Quote
  #11  
Old 07-09-2004, 10:36 AM
Registered User
 
Join Date: Jul 2003
Posts: 555
Ok, I will start by looking at the EGR valve and plugs.
__________________
Thanks, Juan
Reply With Quote
  #12  
Old 07-09-2004, 12:07 PM
Registered User
 
Join Date: Jul 2003
Posts: 555
egr valve and tubing good and clear, plugs white deposits.
running lean.
__________________
Thanks, Juan
Reply With Quote
  #13  
Old 07-09-2004, 12:23 PM
Senior Member
 
Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
Juan,
I concur with all the above comments and advive so no sense repeating. EGR is the major contributer to reducing nitrous oxides and nitrogen dioxides, so be sure the system is funtioning. Apply vacuum to the valve at idle and make the engine run rough or die. Then hook it all up and observe that the EGR needle moves as you race the engine. You can tweak CO up a bit and that will also help. If you have an air pump, it plays a minor part, so make sure it works. Also be sure you are using the grade of fuel the car calls for. If the car calls for premium, combustion temps will increase with faster burning lower grades. All in all I thought those readings were good across the board and NOX isn't that far off. In fact I had a 90 300SEL in the same boat last month and tweaking the CO up got it through.

Good luck,
Peter
__________________
Auto Zentral Ltd.
Reply With Quote
  #14  
Old 07-09-2004, 12:37 PM
Registered User
 
Join Date: Jul 2003
Posts: 555
Thanks Peter, the car does not have an air pump. I will check the timing which I should have done before I took the EGR system apart.
How do you adjust the CO?

I will also fill up with higher grade gas. I have the "cheap stuff" in it right now. No such thing in the Bay Area as you know.
__________________
Thanks, Juan
Reply With Quote
  #15  
Old 07-09-2004, 12:47 PM
Senior Member
 
Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
Sorry Juan,
I know nothing about Toyotas. We pay more for gas than anyone in the country. When they were doing live reporting on that DC serial sniper, I wasn't paying any attention to the reporter. My eyes were fixed on the Shell station behind her with the rediculously low prices.

Peter

__________________
Auto Zentral Ltd.
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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 07:41 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page