Topic: High idle

[dexetr30]

I just replaced my cylinder head. Started it up for the first time a few hours ago. It ran a bit rough and then idled all the way up to 3k +/- a few rpm's. Won't drop back down to normal idle. I checked the codes and I'm getting P0505, IAC. Now, I put my hand over the throttle body and the idle doesn't drop. I don't hear a vacuum leak but the fact that the idle doesn't drop when I do this would indicate to me that there is indeed a vacuum leak. I sprayed some TB cleaner in and around the intake manifold and the idle drops significantly.

So, two questions:

1. Could a vacuum leak cause the computer to become confused and throw the P0505 code?

2. Would the idle dropping when I sprayed the TB cleaner indicate a bad gasket? It drops when I spray it near both the front and rear intake runners where the intake flange meets the head/gasket.

I tend to not believe the p0505 error code because it wasn't idling high prior to the cylinder head replacement.

[sharpxmen]

vac leak for sure.

something's not plugged in where it shoud or your intake manifold is not seated properly on the head. you can listen with a hose around the manifold runners where they meet the head, my first guess would be there, the other guess is some hose is not plugged in, could be the vac line for the brake drum, the CCV line or maybe even the t/b not seated. other one are the IAC not plugged or not working

based on what you said about spraying t/b cleaner and dropping in rpm the manifold is not seated (i suggest not doing that anymore, i'm not sure what's in that t/b cleaner).

[dexetr30]

Yeah, manifold isn't seated properly. I took everything apart and found the dowels for the intake manifold missing. So I'm assuming I didn't get things seated properly. I'm guessing the machine shop removed them. Do you know if the guide dowels are threaded or press in? If threaded, any idea what size. I can really get my head in there to see if there's threads in the holes or not.

Also, does anyone know where I may be able to get new manifold bolts? I looked all over online but nobody seems to have the o.e. style with the spring washers.

Thanks for the response.

[sharpxmen]

the washers are conical and not spring, you can use machine washers or whatever they are called (grade 10 and are thick, same as the ones you find on heavy duty u-bolts for large axles).

the dowel pins are not threaded as far as i know (i pretty sure they're pressed in but i can't confirm) - but it got me thinking how did they removed them, so maybe they are threaded.