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Old 03-28-2017, 04:29 AM   #1
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Boxster losing power

Hi Forum,

After the winter stand stil I realized that my 2,5 boxster 1998 had a hard time raving beyond 4000 rpm at load.
It has no hesitation, misfire or anything else and it starts idle and actually drives quite smoothly.

I notised hat I have two codes which keeps coming back P1123/25 Oxygen sensing limit adaption range 1 ( cyl 1-3) and ( 4-6)

Consequently we did put it on a Dyno , see photo below
were sad results, only 122HP at 5000RPM

The guy stoped the dyne run here explaining that it had sever fuel starvation.
( he had a probe in the exhaust, and I guess that he meassured it to be lean)
I guess that that matches the codes.

Is there any obvious places to look except for the fuel filter.



BR
KIm

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Old 03-28-2017, 06:15 AM   #2
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Look at the Mass Air Flow Filter (MAF) - when this part starts to fail, it often exhibits the symptoms you describe. A quick test is to disconnect the sensor and let the car run using a default map - if it runs better, you know you have a failing MAF sensor.

Porsche Boxster Mass Air Flow Sensor (MAF) Replacement and Troubleshooting - 986 / 987 (1997-08) - Pelican Parts Technical Article
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Old 03-28-2017, 07:14 PM   #3
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Agree - replace fuel filter and do the MAF-disconnect test.
But maybe time for a big service?

If you didn't put Stabil in the fuel, it may have gelled ?
Fuel pressure regulator ?
If the O2 sensors are getting 'old & lazy' ,changing them and the plugs may help.
Air filter?
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Old 03-30-2017, 08:45 AM   #4
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Hi

Thanks for the advises.

Fuel pressure checked today by my mechanic , and it was OK.
The Airflow through the MAF was according to the Mechanic measured to be too low .

I guess that this will reduce the amount of injected fuel accordingly?

New one is ordered and it will be installed tomorrow.

BR
KIm
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Old 03-30-2017, 11:05 AM   #5
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Garage
Make sure rodents have not built a nest in your air filter.
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1998 Boxster with 7.8 DME, 2005 3.6 liter/325 hp, Variocam Plus, 996 Instrument panel
2001 Boxster bought new. Installed used motor at 89k.
1987 924S. 2002 996TT. PST2
Owned and repaired Porsches since 1974. Have driven them all the way the Dr intended...
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Old 03-30-2017, 08:39 PM   #6
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air filter is brand new:-)

br kim
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Old 03-31-2017, 10:30 AM   #7
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Bart,
Slow down.
The only piece of diagnostic data (not performance data) you've got is :
"The Airflow through the MAF was according to the Mechanic measured to be too low "
Please don't feed us info piecemeal and partial. If the Mechanic has done a complete test ,give it to us - the RKAT,FRA ,fault codes - all of it. Otherwise this is just random speculation which will waste time(ours) and money (yours).
Airflow - we need the actual value in gramms.
Meanwhile remove the airfilter and retest briefly .Big change ? Check/clean the TB .You are looking for obstructions.
Please tell us you don't have a K&N (or similar) filter fitted.
Without a Durametric connected and freeze frame data to post this will be difficult to diagnose logically and methodically.

Last edited by Gelbster; 03-31-2017 at 10:32 AM.
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Old 04-03-2017, 06:29 AM   #8
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Power is Back

Hi Gelbster,

Airflow was 90 ltr/sec and the Engine incl filter is all stock.

Anyway the MAF was exchanged and all the power is now back 213 HP /270 NM
Not bad for a 19 year old car which has done 156.000 km :-)

BR
KIM

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