therealcreeper

iTrader: (37)

I've been throwing P0507 for a while now (high idle). I've replaced the IAC motor, all PCV lines & valve, checked the throttle body gasket and still have it.

I currently have ALL vacuum lines coming off the back of the intake plugged (as in the main nipple plugged, no lines come out of it) I don't have AIR or EGR and the line running to the HVAC system cracked so I just plugged the rear of the intake completely.

any ideas what it could be?

ttranssam

iTrader: (10)

your sucking air in somewhere...take starter fluid and spray around the intake and if the idle vhanges then you got a vaccume leak

MyFirstLS1

iTrader: (8)

you said you replaced the pcv lines does this include that "y" piece that connects the two vavle covers to your pcv valve. Mine was all gummy and disintergrated (sp).

after saying that do what he said spray around the mating surface where the intake meets the head. Wonder if it possbile that the intake is cracked from over torque if you have ever had it off.

therealcreeper

iTrader: (37)

I replaced that Y, yes

I have had the intake off twice but both times torqued it in proper sequence and with proper in/lb specs

LS6427

iTrader: (2)

Unplug the PCV vacuum line from the intake vacuum port. Cap it off. If you still have the code that will rule out the entire PCV system.

Check the little black plastic "T" fitting near the PCM that runs the A/C vent system. See if its cracked.

And of course, make sure that line coming off the "T" is still connected to the back of the intake.

Do you "actually" have a high idle along with that code?

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therealcreeper

iTrader: (37)

the back of the intake is completely plugged off, but the line that used to come off of it (to HVAC) is open. I figured it didn't re-enter the system anywhere so I didn't need to cap that.

I'll try to cap off the PCV at the intake but the high idle is very inconsistent so I don't know if I'll be able to tell. safe to run it for a few days with no PCV system?

LS6427

iTrader: (2)

Perfectly safe. I ran 100% without a PCV system for 6 months on my 427ci....zero difference with anything at all. PCV systems are partially BS.

If its inconsistent, maybe the intake has a crack that opens and closes slightly with heating and cooling off cycles.....

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therealcreeper

iTrader: (37)

sprayed around EVERYTHING with not even a blip in idle speed

put a predator on it to watch idle speed:
with PCV system installed regularly: 780-800rpm (looks like 750 on the stock tach)
with PCV capped off at intake mani: 720-740rpm (looks like 600 on stock tach)

rpm's definitely hang a lot longer with the pcv system hooked up after revving, but I pulled the whole thing off and inspected every inch of it with no problems. also tried a different valve and no difference.

is it possible for a bad o2 sensor to be messing with the idle? I would think it would throw a code but I had one in the past that I cleared and never came back and I had a bad exhaust leak at the passenger side header recently which may have been throwing off its reading

LS6427

iTrader: (2)

No, 02 sesnors can't do anything to let more air into the TB so it can rev higher than normal.

3 ways only:
vacuum leak somewhere
IAC must open
Throttle blade must open


Is the TB blade closing all the way, maybe crudded up and dirty. Maybe the cable is binding when its closed or has lost some tension. Make sure its solid as a rock when opening and when its closed. No play at all.

Maybe a crack or hole in the brake booster hose that leads to the back of the intake.

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therealcreeper

iTrader: (37)

I had a similar problem a while back and it was the IAC motor O-ring being missing, so I bought a new one and it went away. I inspected the throttle body and put some silicon around the O-ring to be sure it wasn't that as soon as it started happening and still nothing.

I also sprayed the brake booster hose when I was searching as best I could with no effect, but if it's way in the back it's possible I missed it

therealcreeper

iTrader: (37)

update: I was still convinced it wasn't a vacuum leak and was something that sends a signal to the IAC, so I unplugged the MAF and TPS and now it idles normally. It always hesitated around 1k rpm before coming back to a normal idle but now it revs up and comes right back down normally

I'll replace one and then the other and update which ended up being the culprit

MyFirstLS1

iTrader: (8)

interesting, thanks for the update i have been watching this.

Xtreme57

iTrader: (6)

Updates here? Same problem and no one seems to ever come back to say WTF happened with this. It is one of the most frustrating problems I've had with this car so far...