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Old 09-22-2012, 11:52 AM   #1
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slow rpm drop in neutral and bad gas mileage

I have an 03 Boxster S.

I'm still trying to figure out what's wrong with my car, I had a bad idle which is almost completely gone after cleaning my throttle body, but sometimes the idle will fluctuate a little.

Lately, I've notice my gas mileage around town to be 5 lower than it usually is with the same type of driving. I'm getting 14-15 when I use to get about 18-19. The highway miles I'm still getting 26 -27. My car threw a P0171 code last week after I cleaned thr throttle body, I cleared it and it hasn't come back since.

When my car is in neutral, and i step on the gas, it seems like the car is taking longer than usual to drop back down to 800rpm.

Thoughts?

Last edited by ohhh my; 09-22-2012 at 01:19 PM.
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Old 09-22-2012, 06:30 PM   #2
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need to do mine. was throttle body cleaning difficult? is it hard to reach and disassemble to clean? how many hours did it take you? thanks.
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Old 09-22-2012, 07:30 PM   #3
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I'm no expert, but I'd start with the vacuum lines, sounds like a leak?

When you cleaned the throttle body did you replace the gasket?
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Old 09-22-2012, 08:21 PM   #4
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Originally Posted by tuanle16 View Post
need to do mine. was throttle body cleaning difficult? is it hard to reach and disassemble to clean? how many hours did it take you? thanks.
I would say it's easier than changing oil on a boxster. It will probably take you less than an hour with the right tools. Only special tool needed is a torx set to remove the throttle body.
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Old 09-22-2012, 08:23 PM   #5
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I'm no expert, but I'd start with the vacuum lines, sounds like a leak?

When you cleaned the throttle body did you replace the gasket?
You are probably right. Matter of fact, I don't even recall a gasket.

Dumb question, but which one is the vacuum line? Thanks!
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Old 09-23-2012, 07:18 AM   #6
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Just because it is easy to do, reset your egas by:

With both feet on the floor and nothing touching the gas pedal:

Turn key to the run position (not the cranking position)

Wait until about a minute until you throttle motor run.

Turn key off for 20 seconds or so.

Start car.
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Old 09-23-2012, 03:56 PM   #7
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Paul,
I thought you had to first disconnect the battery (to unlearn what's in the memory) before you reset the e-gas......
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Old 09-23-2012, 04:37 PM   #8
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Nope, but it should be done anytime the battery is disconnected.
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Old 09-23-2012, 04:56 PM   #9
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I tried to remove my TB, but the intake was too hard to remove . How did you remove it?
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Old 09-23-2012, 05:48 PM   #10
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You are probably right. Matter of fact, I don't even recall a gasket.

Dumb question, but which one is the vacuum line? Thanks!
Here's the link for the gasket...
http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=996-110-310-50-M100&catalog_description=Idle%20Control%20Valve%20Gaske t%2C%20Boxster%2FBoxster%20S%20%28%31%39%39%37%2D% 30%34%29%20
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Old 09-23-2012, 09:00 PM   #11
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I tried to remove my TB, but the intake was too hard to remove . How did you remove it?
Which part are you stuck at?

Remove the 4 torx screw on the throttle body itself.

Then loosen the 4 hose clamps. After the hose clamps are loosened, slide them as far out towards the outside of the car as possible. This will give you room to remove the throttle body.
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Old 09-23-2012, 09:31 PM   #12
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i was stuck at just removing the intake hose. i was pulling on it to the point that i feared ripping it. then, i thought to myself, if i can't even get this thing off, how am i going to put it on if i do manage to remove it.
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Old 09-23-2012, 09:34 PM   #13
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i was stuck at just removing the intake hose. i was pulling on it to the point that i feared ripping it. then, i thought to myself, if i can't even get this thing off, how am i going to put it on if i do manage to remove it.
I removed the end that is connected to the intake box first. This will give you leverage to remove the end that is connected to the throttle body. It's fit on there pretty snug, just pull and it will come off.

When I reinstalled everything, I actually connected the intake tube to the throttle body first before I slid everything back in because I found it too hard to push it back in when the throttle body was in place.
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Old 09-23-2012, 09:37 PM   #14
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thanks. i'll try that.
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Old 09-24-2012, 11:18 PM   #15
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yeah the intake pipe was a PITA on mine. came off easy, took forever to push back on.
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Old 09-25-2012, 06:04 AM   #16
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What does "throttle motor run" mean? Thanks
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Old 09-25-2012, 04:22 PM   #17
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the throttle plate in the throttle body is controlled by a small electric motor. when you do the procedure above, the ECU tells the throttle plate motor to run open and closed so that it can learn how far it travelled with a given input. this is your "throttle body basic settings".

with a durametric or factory scan tool, there should be a command to force it to do this.
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