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Old 06-27-2011, 05:59 AM   #1
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'99 Boxster Decelerates, Loses Power?

1999 with 63,000 miles. Car started to decelerate, acted like it was having trouble getting gas, would intermittently surge forward then decelerate. I pulled over shut the car off, restarted
and the car drove fine. No check engine lights.

I replaced the fuel filter. Today, same problem. Car starts to decelerate, I give it gas
but the engine is having trouble revving. I stop and restart, the car runs better and I am able to return home, but doesn't run 100% smoothly. Again, no check engine lights.

Does a fuel pump go bad intermittently? I don't think it's bad gas. Ideas?

Oil cap is not hard to remove when car is running. Engine runs rough with oil cap off and smooths out when replaced.

Thanks.

Anyone, Anyone, Bueller....?


Last edited by keithl; 06-28-2011 at 05:12 AM. Reason: Update.
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Old 06-28-2011, 04:22 AM   #2
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Wow, No one.
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Old 06-28-2011, 04:35 AM   #3
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certainly sounds like fuel starvation could be a cause. Were you having the same issue before replacing fuel filter? If not, might you have missed something upon reassembly or wrong filter or bad one at that? The fuel sending unit/pump is located inside the gas tank but I think you need to confirm fuel filter is OK and do more diagnosis before digging in there.

So, confirm filter good and get the codes read... there might be some pending even though no warning lights. Doing so will get you pointed in a solid direction so you don't have to spend money replacing parts experimentally.

Good luck
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Old 06-28-2011, 04:56 AM   #4
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Oil fouled plugs due to bad O-rings on plug tubes shorting out the sparkplugs?

This is another possibility.

Pull the plugs and see if the insulators are wet from oil.

Cheers!

PS FWIW, it's helpful to state the mileage on your car when seeking advice.
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Old 06-28-2011, 05:04 AM   #5
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Quote:
Originally Posted by Lil bastard
Oil fouled plugs due to bad O-rings on plug tubes shorting out the sparkplugs?

This is another possibility.

Pull the plugs and see if the insulators are wet from oil.

Cheers!

PS FWIW, it's helpful to state the mileage on your car when seeking advice.
63000 Miles. Just changed the plugs at 62,000 and there wasn't any oil in there. Fuel filter was changed after the first episode. Thanks.
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Old 06-28-2011, 07:10 AM   #6
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I don't believe...

Quote:
Originally Posted by keithl
63000 Miles. Just changed the plugs at 62,000 and there wasn't any oil in there. Fuel filter was changed after the first episode. Thanks.
... in coincidences.
If you replaced the sparkplugs at 62K and now at 63K you have these issues, there has to be a connection.
One of your coils could be not connected properly (but the CEL would have indicated that).
Is your CEL working?
Did you remove/clean the MAF at that time?
Sure sounds like a MAF issue.
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Old 06-28-2011, 07:21 AM   #7
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Quote:
Originally Posted by ppbon
... in coincidences.
If you replaced the sparkplugs at 62K and now at 63K you have these issues, there has to be a connection.
One of your coils could be not connected properly (but the CEL would have indicated that).
Is your CEL working?
Did you remove/clean the MAF at that time?
Sure sounds like a MAF issue.
Happy Boxstering,
Pedro
Thanks. I'm only assuming the CEL is working. I have not cleaned the MAF, I will try that. Thanks.
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Old 06-28-2011, 07:37 AM   #8
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I don't have CEL coming on... do I have to disconnect the battery to clean the MAF sensor? Also, is there a certain mileage that it should just be replaced? thanks

Last edited by keithl; 06-28-2011 at 07:44 AM. Reason: addtion
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Old 06-28-2011, 08:15 AM   #9
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you dont have to disconnect the battery, just pull the maf. easy way is just to unplug the MAF and drive. if the problem is still there, then it is not the MAF.
Does not hurt to clean it though. you will need tamper proof torx heads.
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Old 06-28-2011, 09:20 AM   #10
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I just had similar problem with my 2001. It would usually run fine, but sometimes I would feel it lose power. When I stepped on gas pedal, no response. sometimes it would die and wouldnt start for a while. No cel lights ever came on, porsche repair shop dumbfounded. Finally died and had towed immediately. Turned out it was the fuel pump. Had it replaced and good ever since.
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Old 06-28-2011, 09:37 AM   #11
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Quote:
Originally Posted by rgriffin
I just had similar problem with my 2001. It would usually run fine, but sometimes I would feel it lose power. When I stepped on gas pedal, no response. sometimes it would die and wouldnt start for a while. No cel lights ever came on, porsche repair shop dumbfounded. Finally died and had towed immediately. Turned out it was the fuel pump. Had it replaced and good ever since.
Interesting, I will look into that next. I thought it might be my fuel pump, but never had one work intermittently before. Thanks.
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Old 06-28-2011, 04:58 PM   #12
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When my fuel pump failed the car had the same symptoms just as you described. It had loss of power when trying to accelerate and then surge spastically. I had to slow down to maintain a drivable condition then I was able to get to my destination (repair shop) before it completely died and wouldn’t start. I'm glad to say it didn't leave me stranded.
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Old 06-29-2011, 05:06 AM   #13
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Quote:
Originally Posted by Jager
When my fuel pump failed the car had the same symptoms just as you described. It had loss of power when trying to accelerate and then surge spastically. I had to slow down to maintain a drivable condition then I was able to get to my destination (repair shop) before it completely died and wouldn’t start. I'm glad to say it didn't leave me stranded.

Thanks. Yep that's sounds like mine. I cleaned the MAF (which didn't seem dirty at all) and the car drove fine after that. But my problem has been intermittent, and since the
CEL didn't come on it makes my think it could still be the fuel pump.
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Old 06-29-2011, 07:15 AM   #14
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Quote:
Originally Posted by keithl
since CEL didn't come on it makes my think it could still be the fuel pump.
Test to see if the CEL works. It may be burnt and you could have a bunch of codes.
Switch the ignition on (without starting the car) and see if the CEL lights up.
If it doesn't it may be out.
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Old 06-29-2011, 11:41 AM   #15
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Quote:
Originally Posted by ppbon
Test to see if the CEL works. It may be burnt and you could have a bunch of codes.
Switch the ignition on (without starting the car) and see if the CEL lights up.
If it doesn't it may be out.
Happy Boxstering,
Pedro
Thanks!
It actually does come on with the other lights. Will there be codes there even if the CEL isn't on? Does it sound like a flakey fuel pump if the CEL isn't coming on?
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Old 03-05-2014, 05:30 PM   #16
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Quote:
Originally Posted by keithl View Post
Thanks!
It actually does come on with the other lights. Will there be codes there even if the CEL isn't on? Does it sound like a flakey fuel pump if the CEL isn't coming on?
Was this resolved? I'm having a very similar issue with a 987.

I will shift (downshift or upshift, doesn't matter), and once in the new gear the car acts like the gas pedal isn't even connected. Like tonight at a green light I had it in first and it started moving then it acted like the gas pedal wasn't even connected, so I shifted to 2nd and it acted normal again. Seems shifting fixes it, but I don't want to always have to shift, it should have power in the gear I'm in. Happened in 5th too, I even floored it and pumped the peddle, just acted like the gas pedal was connected to nothing but I could hear the peddle hit the floor, but as soon as I shifted to 4th it behaved normal again.
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Old 03-06-2014, 11:13 AM   #17
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Porsche shop was finally able to reproduce the issue. They're saying it could be pedal sensor? Diagnostic computer did not detect anything when vehicle lost acceleration. Sensor is never suppose to fail so no dealers in area have on hand, will take a week to get one and installed.

I'll update if that solves the problem, I'm just glad they were finally able to reproduce the issue themselves because there is nothing worse than bringing a car to a shop and they say that they don't see anything wrong.
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Old 03-06-2014, 11:18 AM   #18
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Intermittent problems are the worst. They always disappear the moment the mechanic gets behind the wheel.
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Old 03-06-2014, 12:00 PM   #19
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Intermittent problems are the worst. They always disappear the moment the mechanic gets behind the wheel.
Completely agree.

Most people curse that check engine light coming on but they have no idea how much worse it is when something happens and a light does not come on.

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