I have this problem with the 2008 Impala, V6, 3.5 liter
Currently throws code P0507, (Idle Air control system, Engine Speed Higher than expected)
For a while there was "engine power reduced" on and off
Yesterday, after "engine power reduced" massage, lost power and engine died, new massage was "starting disabled" and "service throttle"
Could not start immediately, but started after a few minutes.
Car came to me, I removed and cleaned throttle, there was some carbon but not much, checked throttle as much as I can do, including motor nad potentiometer (s)
Reinstalled, cleared the codes, it had P0128, P0172, P2122 & P2127.
Engine power message is not there but now, car has Idling problem.
Problem is that when started, it has about 1500 RPM, which drops after 10 to 15 second to normal 700 rpm or so, but
when you step on the accelerator and bring to 1500 or 2000 RPM and remove the foot from the pedal, it stays at high idle, 1500, sometimes after minute drops down to 1100 and then to normal 690 to 700 RPM, but not all the time. Turning it off nad starting brings the Idle to normal.
Removed the throttle and checked all again, can not see much wrong with throttle, can not see any hoses disconnected or else

Have this OBDII interface, so I can tell that at 700 RMP, Tp (position) is about 17%, MAF is 4.02 gm/s, when it is at high idle 1500 RPM, Tp is 25% and MAF is 9.26 gm/s.

This could be something simple, but I can not figure this out and need your help, which will be appreciated.

Thanks,

Ziggie

 

Hi,

Did some more reading, was looking for vacum leaks, suspected brake vacum buster or PCV system, (valve, hose)
Disconnecting the PCV hose and plugging it, disconnecting breake buster hose and plugging it, buth seem to fix idle problem.
Read more book, did the PCV system check, plugged fresh air intake, use oil dipstic tube for vacume gauge, no Idle problem, at 1500 RPM vacum slowly builds up in the engine, to about 10 inch, which book says is good.
I suspect this is combination, PCV valve lets too much air, probably breake buster too. Replaced some o-rings on PCV tube, seems to work now, no idle problem,
Go figure, I just do not know, just learning.
Buddy says that he replaced breake vacum buster about year ago.

Ziggie

 

Found post by EinST from 03-30-2011, suggests to do Throttle / Idle Learn Procedure, given link did not work, found TSB on the net, will try that tomorow, when my buddy brings car back to me, stil lhas idle problem

Ziggie

 

I think this is it, one of the TSB on Ilde Relearn,

http://www.google.ca/url?sa=t&rct=j&...5tvtGOpsHLbuZQ

Ziggie

 

Where would I get electrical (complete) schematic for this vehicle?

 

This was solved by replacing Gas Pedal, from the dealer, not aftermarket.

Ziggie

 

Wiring for this vehicle are available on Autozone site, free, need to register only.

Ziggie

 

Ziggie,


Did you ever get this High Idle figured out? I have the same problem with my 2008 Impala LS. Mine acts the same way you described but no engine light alarms or codes. I did notice that it only happens when the car is moving either forward or backwards more than 1 mile per hour. Seems like when the transmission is moving it kicks my engine into high idle even in neutral. Once the car has completely stopped for about 5 seconds it idles back down to normal around 800. If on a slight grade and I let the car start rolling in neutral or in gear it kicks into high idle. Can't understand why the transmission moving/rolling would tell the car to go to high idle.


Any feed back would be great.


Thanks!


Marc

 

sounds like you and I have the same car...any solution?