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Old 07-20-2005, 09:35 AM   #1
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guys, I have done the Chevron additive and gas, put in the new MAF and tightened up my intake making sure all is snug and no leaks. The idle regulator seems fine, I believe this to be true because when I have a cold start the car does not have the "hunting idle" issue until it warms up. anymore suggestions???
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Old 07-20-2005, 12:01 PM   #2
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Quote:
Originally Posted by psuball1
guys, I have done the Chevron additive and gas, put in the new MAF and tightened up my intake making sure all is snug and no leaks. The idle regulator seems fine, I believe this to be true because when I have a cold start the car does not have the "hunting idle" issue until it warms up. anymore suggestions???
Unfortunately you're getting to a point of replacing parts if you don't have any diagnostics tools. If you really want to get into it, the AutoTap does a great job with reading the sensors while the engine is running. They have two types, one that connects to a computer through USB and the other connects to a Palm device. Great product for $180. http://www.autotap.com It's not a miricle worker though. You have to take a little time to learn how to understand the readings it gives you.

There are several things that can cause the changing idle. Most often it's a vacuum leak or bad PCV valve. Next is O2 sensor. Next is bad MAF sensor. Basically sensors that adjust the fuel/air ratio. Then there are other sensors that are much less likely to cause that problem, like the knock sensor, but it is possible. The easiest way to figure it out is to plug it in and see what is changing as it goes up and down. Otherwise you just have to start swapping parts.

O2 sensor swaps can help and I think they are pretty easy to replace on the Boxster. If you decide to replace them, start with the ones before the cats. Buy just one and pick the one to replace. Keep the old one and see if it takes care of the problem. If not, swap the one you took out with the next one. If neither fixes it, go to the O2 sensors after the cats and do the same thing. Check because I think the after sensors are different from the before. If none of that works, don't worry, O2 sensors only last about 100K miles so you have replacements for the future.

Other than that, without any kind of readings it's a guessing game.

Good luck!
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Old 07-21-2005, 10:15 AM   #3
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The O2 sensors are next on the list. If the check engine light does not come on is it still possible to have a defective O2 sensor? Is there a way to check them?
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Old 07-21-2005, 11:35 AM   #4
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Quote:
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The O2 sensors are next on the list. If the check engine light does not come on is it still possible to have a defective O2 sensor? Is there a way to check them?
Yes, it is possible. The only way to check the sensor is to plug into the OBD system and read the output of the sensors. They change their voltage output to change the volume of air in the fuel/air mix. You have to see if the output voltage is going up and down along with the up and down changes in the idle. AutoTap does those readings.
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