High idle - need help figuring out what to do next

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xourque
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Joined: Wed Jul 29, 2015 10:01 am

High idle - need help figuring out what to do next

Postby xourque » Wed Jul 29, 2015 10:17 am

Hello, all!

I have been dealing with the P0507 high idle code for a few months now.

There are plenty of possible problems and associated solutions, but I'm trying to my best to this intelligently, and not "just do a bunch of things" to try and fix it. Keep in mind I've tried doing the relearn process many times. It will seem like it's ok until I drive it around for more than 5 minutes and the idle speed will go back up and the code will go again.

SYMPTOMS TO NOTE:
- It idles between 850 (warmest) and 1,100 RPM (coldest) - never any higher than that.
- When I turn the car on, the tachometer bounces up above 1,500 rpm before going lower. Makes me think it's a vacuum leak...
- I've been hearing some awful pinging noises SOMETIMES when accelerating hard - only when I have the windows down can I hear it.
- Gas mileage seems normal.
- Performance seems normal.
- I don't detect ANY problems with my throttle, it has been responsive and absolutely fine the whole time.

In reading many forum postings around the internoodles, it seems like it ends up being either:

1) A vacuum leak
2) A throttle position sensor / whole throttle body problem
3) The Idle Air Control Valve

Here's what I've done so far to no avail:

- Cleaning the MAF sensor with MAF cleaner - it didn't look dirty at all.
- Cleaning the throttle body with seafoam - it looks quite clean.
- Running some seafoam into the brake booster line - it didn't fix it but my car definitely runs smoother.
- Looked everywhere for a vacuum leak but couldn't find a darn thing wrong.

Clues/background:

- MOST IMPORTANT CLUE: Months ago before THIS problem started, whenever I'd start the car, it'd nearly die but then idle absolutely fine/happy. Just after starting the car it'd idle extremely low and either die or come back up to normal 750 rpm operation. This randomly went away - and now I have the high idle P0507 issue.
- Between the time it would start and almost die and now, is I had the brake system serviced - they flushed the fluid, replaced front rotors and pads, and repacked the front wheel bearings.

So....I NEED HELP!! What do you think it is? What should I try next?

Other details to note:
- 160k miles
- 60k miles on the current set of spark plugs
- I use a K&N air filter
- O2 sensors are all still original - haven't ever replaced them
- I recently replaced the rear trailing control arms because the bushings were awful - I also put on a set of four new shocks
- No other symptoms or problems with the car...it drives great for its age!

Thank you ALL in advance for your time!!


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