Idle problem

[srietscha]

I had a valve problem on #7 that I got fixed. Ever since I put the motor back in the idle has been messed up. The car is kicking out P1504 Manufacturer contolled vehicle speed, idle control and auxilary inputs. I also get a P1506 code which was similar. I've replaced the Throttle position sensor, IAC, and checked for vacuum leaks using ether. I also tried a different computer. Right now the idle just bounces around all over the place. It will go anywhere from 400 to 1200 at idle. It runs great on the highway, but the idle speed is seriously messed up.

Whats the vacuum line from the air intake tube that connects with a vacuum from the front valve cover do to a fitting that bypassses the throttle body do? I'll get a picture when I can. I had to to replace a broken fitting and a couple dry rotted vacuum lines there and it seems to control idle speed somewhat.

 

[luigisho]

Get a picture. Could be the pcv from both valve covers that T together and go to the intake hose.

 

[SHOZ123]

Odd codes. Haven't seen these before personally.

DTC P0505, P1504, P1507 OR STARTS ONLY AT PART THROTTLE: CHECK VPWR TO IAC VALVE ASSEMBLY

DTC P0505 indicates that Self-Test has detected an IAC system malfunction.

DTC P1504 indicates that Self-Test has detected an IAC circuit malfunction.

DTC P1507 indicates that Self-Test has detected an IAC underspeed error.

Note: If EGR DTC P0402 was output during Quick Test, diagnose it first before continuing with this Pinpoint Test (Refer to Section 4A, Diagnostic Subroutines ).

Possible causes:

IAC circuit open.
IAC circuit shorted to PWR.
IAC circuit short to GND (P1507).
VPWR circuit open.
Air inlet plugged (P0505, P1507).
Air inlet leakage (P1507).
Damaged IAC valve assembly.
Damaged throttle body (P0505, P1507).
Damaged PCM.
Key off.
Disconnect IAC valve assembly vehicle harness connector.
Key on.
Measure voltage between VPWR circuit at the IAC valve assembly vehicle harness connector and battery ground.
Is voltage greater than 10.5 volts?


DTC P1506: CHECK FOR VACUUM LEAKS
Diagnostic Trouble Code (DTC) P1506 indicates Self-Test has detected an IAC overspeed error.

Possible causes:

IAC circuit short to GND.
IAC valve assembly stuck open.
Vacuum leak.
Damaged IAC valve assembly.
Damaged throttle body.
Damaged PCM.
Key on, engine running.
With the engine at idle, listen for vacuum leaks.
Inspect the entire intake air system from the Mass Air Flow (MAF) sensor to the intake manifold for damage or leaks such as:
Cracked or punctured intake air tube.
Loose intake air tube at the air cleaner housing or throttle body.
IAC valve assembly or gasket seal.
Intake manifold assembly or gasket seal.
EGR valve gasket seal.
Vacuum supply connectors and hose.
PCV valve, connectors and hose.
Are any leaks detected in the above areas?

 

[Silvapain]

Could also be a pinched IAC control wire.

 

[srietscha]

Thanks for the help. I'm thinking I may have a vaccum in the wrong location. I'm not sure where the vacuum hose from the rear valve cover is. It doesn't look like the two valve cover vacuum hoses are tied together.

 

[srietscha]

Does anyone have a good vacuum schematic? I have a shop manual, but it isn't real clear to me.

 

[luigisho]

v8sho.com can be useful
here are some pictures for ref.

http://v8sho.com/SHO/RearCOPReplacementPhotosandHowTo.htm

So note that in picture #1 the vacuum hose from the front valve cover is just behind the thick loom in front--- in front of the intake runner furthest to the right. You can barely make out the 't' fitting that runs from a hose (connected to the exact looking counterpart fitting from the rear valve cover) underneath the metal bracket with 3 fasteners that has a thicker hose routed over the top of said bracket.
The "2" valve cover pcv openings merge and are attached to the hose that runs and attaches to the intake hose, before the throttle body, the hole closer to you facing the motor. Any of that make sense at all?

 

[srietscha]

Thanks Luigisho. That does make sense and the pictures are helpful. I'm at work right now, but I'm pretty sure that's where my problem is.