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

Reply
 
LinkBack Thread Tools Display Modes
Old 04-12-2016, 04:41 AM   #1
Registered User
 
Join Date: Sep 2014
Posts: 30
Drop in gas mileage - unknown cause

Hey all, my 2002 Boxster S has been running at lower efficiency, and seemingly lower power, for a few weeks, and I'm now getting around to chasing down the source of the problem. I noticed that my mileage used to be around 20-23 mpg in the city (27-29 highway) but it has since dropped to around 15 mpg. In addition, there seems to be a slight drop in power as well as a faint unburnt fuel smell coming from the exhaust. There is no check engine light.

Any ideas on how I can chase down this issue? Has anyone had this happen before?

Note that my car did get hit at low speed in the front end a few days ago, but I think that this is independent because the issue popped up weeks ago.

Thanks for your help!
TuftsAuto is offline   Reply With Quote
Old 04-12-2016, 10:55 AM   #2
Registered User
 
Join Date: Dec 2009
Location: Orange County, CA
Posts: 1,228
Quote:
Originally Posted by TuftsAuto View Post
I noticed that my mileage used to be around 20-23 mpg in the city (27-29 highway) but it has since dropped to around 15 mpg. In addition, there seems to be a slight drop in power as well as a faint unburnt fuel smell coming from the exhaust. There is no check engine light.
Tufts

When was last time you replaced your air filter, spark plugs, etc..?

Usually when you neglect these, the mileage and the performance goes down pretty quick, hopefully is something this easy
Gilles is offline   Reply With Quote
Old 04-12-2016, 11:18 AM   #3
Registered User
 
Join Date: Sep 2014
Posts: 30
Thanks for the tip. I changed the air filter six months ago, but haven't swapped spark plugs. The car has 77K miles on the body, but the engine was factory-replaced after an IMS bearing failure at ~40K miles (need to look up exact amount).

What is the cost and procedure (time to do at home) of changing spark plugs?
TuftsAuto is offline   Reply With Quote
Old 04-12-2016, 02:42 PM   #4
Registered User
 
Steve Tinker's Avatar
 
Join Date: Dec 2008
Location: Queensland, Australia
Posts: 1,522
About 2 hours to replace plugs - cost is minimal as the Bosch or Beru plugs are standard items. You need to jack up the rear of the car install jackstands and remove part of the wheel arch plastic liner + moulding for access to the coil packs and plugs.

A few years ago I had the same symptoms as you, plugged in the trusty Durametric and found the MAF below limits. Replaced and performance + fuel economy back to normal.
__________________
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 04-12-2016, 02:56 PM   #5
Artist, 986S tinkerer
 
NewArt's Avatar
 
Join Date: Aug 2013
Location: Montreal, Canada
Posts: 1,529
Quote:
Originally Posted by Steve Tinker View Post
A few years ago I had the same symptoms as you, plugged in the trusty Durametric and found the MAF below limits. Replaced and performance + fuel economy back to normal.
Steve, did that throw a code?
__________________
James
2004 986 S
987 air intake TB and plenum, Mantissport 2 litre sump, UDP, Bilstein B6 with H&R lowering spings, re71-rs for track, other stuff.
https://www.youtube.com/user/12shoes2
NewArt is offline   Reply With Quote
Old 04-12-2016, 11:53 PM   #6
Registered User
 
Steve Tinker's Avatar
 
Join Date: Dec 2008
Location: Queensland, Australia
Posts: 1,522
No it didn't - the only way I found it was by using the Durametric.
The performance had fallen off slightly so I plugged it into the diagnostic port. The big difference was with the new MAF - everything was better (economy + low / mid range performance) it felt like a different car. Who'd have thought......
__________________
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 05-06-2016, 09:13 AM   #7
Registered User
 
Join Date: Sep 2014
Posts: 30
Thanks for the tip! I cleaned out the MAF using standard MAF cleaner spray and the car is like new. Improved gas mileage and throttle response. Possibly a bit quicker too.
TuftsAuto is offline   Reply With Quote
Old 05-07-2016, 03:29 AM   #8
Registered User
 
Steve Tinker's Avatar
 
Join Date: Dec 2008
Location: Queensland, Australia
Posts: 1,522
Good to hear you had some success.....
__________________
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
Reply


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 11:04 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, 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