05-06-2011, 10:40 PM
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#1
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Registered User
Join Date: Mar 2010
Location: australia
Posts: 5
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Help!!..misfire no CEL
HI.. need some help
have a intermittent misfire below 2000rpm on my 2002 2.7 manual Boxster.
I removed the throttle body 2 weeks ago and cleaned it, since then have a misfire at low revs. No CEL , just rough running.Clears over 2000 rpm, but misfires badly when it drops below this.Does not happen all the time, will run fine for 5 km or so, then misfire.
Any suggestions??
thanks
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05-09-2011, 06:18 AM
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#2
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Registered User
Join Date: Aug 2007
Location: Tustin Ca.
Posts: 449
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You might check the coil packs and wires. Long shot , doesn't quite fit the symptoms but coils can do funny things.
Regards, PK
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05-09-2011, 08:24 AM
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#3
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Registered User
Join Date: Dec 2006
Location: shoreham, ny
Posts: 1,619
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Coil packs and make sure when you replace them that they are definately plugged all the way in.
__________________
996 3.4 engine with 2.7 986 5speed transmission
Ebay Headers, Fabspeed high flow cats, JIC Cross, IPD Plenum, H&R Coilovers, B&M Short Shifter, AEM Uego Gauge Type Analog, Apexi S-AFC Select, 987 air box, Litronics, 2000 Tails and side markers, painted center console, 18" 987 S-Wheels, GT3 Front bumper with splitter.
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05-09-2011, 02:54 PM
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#4
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Registered User
Join Date: Dec 2008
Location: Queensland, Australia
Posts: 1,522
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If the missfire happened after you removed the throttle body for cleaning, I would also go over your work and double check all the connections, both electrical and vacuum lines
__________________
2001 Boxster S (triple black). Sleeping easier with LN Engineering/Flat 6 IMS upgrade, low temp thermostat & underspeed pulley.
2001 MV Agusta F4.
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05-10-2011, 10:48 AM
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#5
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Certified Boxster Addict
Join Date: Nov 2010
Location: Los Angeles
Posts: 7,669
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Misfiring is usually related to an issue with the engine timing or fuel/air mix. Usually, you'll get a CEL if the fuel/air mix is off (this is what the O2 sensors monitor), so the first place to look for a misfire with no CEL is the engine timing:
The input comes from the crankshaft position sensor. If this sensor isn't working reliably, the timing will be off.
The output is through the coil packs/wires. If either of these aren't working properly, the timing will be off.
__________________
1999 996 C2 - sold - bought back - sold for more
1997 Spec Boxster BSR #254
1979 911 SC
POC Licensed DE/TT Instructor
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05-10-2011, 11:08 AM
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#6
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Registered User
Join Date: Sep 2009
Location: The City
Posts: 1,084
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what if the lead up to this was a bad maf which lead to a rich af ratio. could it be fouled plugs? i only ask, im not trying to hijack, ive just had similar problems.
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05-10-2011, 12:33 PM
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#7
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Registered User
Join Date: Dec 2010
Location: Hot Springs Village, Arkansas
Posts: 245
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Because it's cheap and easy I'd first disconnect the battery and then follow the procedure for a throttle "relearn/recalibration". Hook up the battery, turn the key on but don't start the motor, leave key on for 60 seconds, turn off key and remove.
And don't woryy about the CEL - it'll come on eventually, lol. The other poster who suggested a vacuum leak due to a detached vacuum line could be right though.
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05-11-2011, 03:20 AM
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#8
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Registered User
Join Date: Mar 2010
Location: australia
Posts: 5
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thanks for the replies..appreciate it
have booked it in tomorrow at the local Porsche dealer..will let you know what they find
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05-13-2011, 01:05 AM
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#9
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Registered User
Join Date: Mar 2010
Location: australia
Posts: 5
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Jaay was right..loose coil pack on number 5
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