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

Post Reply
 
LinkBack Thread Tools Display Modes
Old 06-28-2014, 05:46 PM   #1
Beginner
 
Jamesp's Avatar
 
Join Date: Mar 2013
Location: Houston
Posts: 1,659
Garage
My Boxster is acting like an idiot

After an engine rebuild, the idle was at 800 rpm after the fuel trims caught up to the rebuild. The idle has slowly fallen since then and now sits at a stable 650. A couple of day ago it stalled in a parking lot at closed throttle. Now it has stalled while driving, always at closed throttle. At closed throttle in a parking spot the idle began swinging wildly between 400 and 2000 rpm until the engine died. That took about 10 seconds. Driving after that it began choking and at ~4500 rpm with the engine stuttering and essentially shutting off and then restarting at lower RPM. It has begun to surge almost imperceptibly at 3000 rpm while cruising. I put 5 gallons of gas in it and it ran like a champ to 7K rpm, except for the slight surging. Other than exorcism, any ideas what the problem might be?

The car sat for ~ 3 years after an IMS failure. Complete engine rebuild and it's been on the road ever since.

__________________
2003 S manual
Jamesp is offline   Reply With Quote
Old 06-28-2014, 06:54 PM   #2
Porsche "Purist"
 
Paul's Avatar
 
Join Date: Aug 2003
Location: Wisconsin
Posts: 2,123
Garage
round up the usual suspects:

fuel pressure

ignition switch

vacuum leaks

loose wiring
__________________
1998 Boxster with 7.8 DME, 2005 3.6 liter/325 hp, Variocam Plus, 996 Instrument panel
2001 Boxster original owner. I installed used motor at 89k.
1987 924S. 2002 996TT. PST-2
Owned and repaired Porsches since 1974. Porsche: It's not driving, it's therapy.
Paul is offline   Reply With Quote
Old 06-29-2014, 04:26 AM   #3
Beginner
 
Jamesp's Avatar
 
Join Date: Mar 2013
Location: Houston
Posts: 1,659
Garage
I was hoping someone might narrow it down with the following symptoms/clues:

1) idle (low, and now surging and falling until the car stalls)

2) now occasionally crapping out at high RPM (right around Variocam actuation - ~4500 RPM)

3) a little bit of surging under load at any RPM at all times. (barely noticeable)

4) Put in 5 gallons of gas and the car is magically "fixed", Coincidence?

5) and its getting worse as time progresses

Anyone have insight or a good guess at what problem or failing component would account for all of the above?.

No check engine light

2003 S manual transmission
__________________
2003 S manual
Jamesp is offline   Reply With Quote
Old 06-29-2014, 04:47 AM   #4
Porsche "Purist"
 
Paul's Avatar
 
Join Date: Aug 2003
Location: Wisconsin
Posts: 2,123
Garage
Fuel pump (See list: fuel pressure)
__________________
1998 Boxster with 7.8 DME, 2005 3.6 liter/325 hp, Variocam Plus, 996 Instrument panel
2001 Boxster original owner. I installed used motor at 89k.
1987 924S. 2002 996TT. PST-2
Owned and repaired Porsches since 1974. Porsche: It's not driving, it's therapy.
Paul is offline   Reply With Quote
Old 06-29-2014, 10:40 AM   #5
Registered User
 
BYprodriver's Avatar
 
Join Date: Oct 2008
Location: O.C. CA
Posts: 3,709
Garage
Quote:
Originally Posted by Jamesp View Post
I was hoping someone might narrow it down with the following symptoms/clues:

1) idle (low, and now surging and falling until the car stalls)

2) now occasionally crapping out at high RPM (right around Variocam actuation - ~4500 RPM)

3) a little bit of surging under load at any RPM at all times. (barely noticeable)

4) Put in 5 gallons of gas and the car is magically "fixed", Coincidence?

5) and its getting worse as time progresses

Anyone have insight or a good guess at what problem or failing component would account for all of the above?.

No check engine light

2003 S manual transmission
Sounds like fuel delivery problem, wouldn't hurt to do the throttle initalization process: Turn key to on for 1 minute without touching gas pedal, turn key off for at least 10seconds, then you can start engine as normally.

Check for pending trouble codes, use drive links to disable fuel injectors 1 at a time.
Lot's of 986 fuel pumps aging out these days, also might try a simulated fueling procedure without actually adding any fuel to see if you get the same positive results.
__________________
OE engine rebuilt,3.6 litre LN Engineering billet sleeves,triple row IMSB,LN rods. Deep sump oil pan with DT40 oil.

Last edited by BYprodriver; 06-29-2014 at 10:47 AM. Reason: sp.
BYprodriver is offline   Reply With Quote
Old 06-30-2014, 07:10 AM   #6
Registered User
 
jb92563's Avatar
 
Join Date: Apr 2012
Location: Riverside, CA
Posts: 1,665
I feel your pain, as I'm having similar problems. -how-diagnose-resolve-engine-issues-using-durametric

It could be the MAF. Try unplugging it and go for a short drive.

If everything has settled down then you know its a MAF problem,
and a very easy fix.

Try cleaning it first ONLY with MAF cleaner spray as anything else tends to make matters worse.
Many folks get more time after cleaning but it seems that only a replacement fixes it for the longer term.

I have to admit that is sounds a lot like a fuel delivery or regulator issue but start with the easy cheap fixes first.

PS: Auto Zone will loan you a fuel pressure tester for free and its easy to test with the fuel rail Schroeder cap being on the passenger side.

__________________
"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)

Last edited by jb92563; 06-30-2014 at 07:18 AM.
jb92563 is offline   Reply With Quote
Post 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 04:52 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page