Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical chat

LinkBack Thread Tools Display Modes
Old 07-09-2014, 12:09 PM   #1
Registered User
Join Date: May 2014
Location: Ireland
Posts: 6
2002 Boxster S 986 : MOT Emissions Failure


My car has just failed its MOT on exhaust emissions.

The acceptable lambda range is listed as between 0.97 and 1.03.

My car tested at Lambda 1.06.

The test is listed as High Idle (3,071rpm) ,it appears to have passed the low idle (680 rpm)

I have no lights on the dash and have connected up my ODB reader (Torque Andriod) and have no codes stored on the car.

I would be very gratefull if anyone can point me in the direction as to what my problem may be, as I dont want to spend a fortune on the car at a dealer if at all possible.

In the past three months I changed all the spark plugs and coils packs and the car has covered 6000km with no faults.

I presume it is safe to continue driving the car?


Last edited by ajg986driver; 07-09-2014 at 12:11 PM.
ajg986driver is offline   Reply With Quote
Old 07-10-2014, 06:35 AM   #2
Registered User
jb92563's Avatar
Join Date: Apr 2012
Location: Riverside, CA
Posts: 1,664
With no codes the car thinks everything is within acceptable parameters.

Check the cheap things first if it is the emissions out of limit and not just a faulty sensor:

Check the engine air filter.
Clean the MAF sensor with ONLY a MAF cleaner.
Check for air leaks in the induction system and all hoses connected to it.
Check for Exhaust header leaks.

Did they identify which lambda sensor was reading too high? A faulty sensor?
There are 4 sensors and easy to replace if they are known to be bad, but a little pricey if you have to do all 4.

Its a common error to replace a sensor when it is not at fault but the reading was out of spec due to an engine air/fuel issue.

Without a code or diagnostic reading of the long term and short term fuel trims its hard to figure out what is going on.
"It broke because it wants to be Upgraded "
2012 Porsche Performance Driving School - SanDiego region
2001 Boxster S, Top Speed muffler, (Fred's) Mini Morimotto Projectors, Tarret UDP,
Short Shifter, Touch Screen Dual Din Radio, 03 4 Bow glass Top (DD & Auto-X since May 17,2012)
jb92563 is offline   Reply With Quote
Old 07-12-2014, 03:24 AM   #3
Registered User
Join Date: May 2014
Location: Ireland
Posts: 6
Thanks for your reply.

No they only tested with a probe in the exhaust to get the lamda readings for the test so no actual tests were performed on the O2 sensors themselves.

Agree it is difficult to with any codes being thrown to point in the direction as to what the cause is.

I will def check the air filter and MAF.
ajg986driver is offline   Reply With Quote
Old 07-12-2014, 08:47 AM   #4
Registered User
amagalla's Avatar
Join Date: Nov 2009
Location: San Jose , CA
Posts: 519
How hot was the engine? the Cats work best when they are really hot. If they let it sit for an hour and then brought the car in for testing, that might make a difference. You might also want to try cleaning the intake.

These are just the basics.
Good luck.
Lapis Blue 03 Boxster S
Seal Grey 04 Boxster S (RIP 9-21-14)
amagalla is offline   Reply With Quote
Old 07-12-2014, 02:27 PM   #5
Registered User
Steve Tinker's Avatar
Join Date: Dec 2008
Location: Queensland, Australia
Posts: 1,522
Originally Posted by jb92563 View Post

There are 4 sensors and easy to replace if they are known to be bad, but a little pricey if you have to do all 4.
He lives in Ireland (ROW spec) where they have only have 2 cats / sensors to check or replace.
That makes it a little easier on the checking and or wallet.....
2001 Boxster S (triple black). Sleeping easier with LN Engineering/Flat 6 IMS upgrade, low temp thermostat & underspeed pulley.
2001 MV Agusta F4.
Steve Tinker is offline   Reply With Quote
Old 07-12-2014, 08:42 PM   #6
Registered User
Join Date: Mar 2014
Location: Eastern NC
Posts: 627
My first thought when reading reading this was to wonder what if the cam deviations are in spec due to worn chain pads. Do you happen to know what the chain devition is or could anyone comment if they would cause this probelm?

BFeller is offline   Reply With Quote

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 -8. The time now is 08:33 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page