i just installed a lingenfelter cai on my z, and while i was at it, i took the throttle body off and cleaned it really well. it was pretty funky. it took about 30 minutes to get it all silver, but it looks good as new now.

i checked and all the vacuum lines are good, i made sure to connect everything back the way it was.

i just replaced the IAC about 3 or 4 weeks ago.

the car is idling at an indicated 1200 rpm when in park or neutral, whether it's warmed up or not.

at first i thought maybe it was the enhanced airflow and the computer would just take a while to learn to tone it down a bit.

but then today the SES light came on. so i knew something wasn't right. i disconnected the PCM fuse for a few minutes and put it back, the SES light is gone but it's still idling high.

literally, i can let off the brake on a level road, and it'll idle forward at 25 mph.

it doesn't move up and down. i thought maybe the throttle stop screw needed backed off, so i did that, and it brought it down a little bit. from 1400 rpm to the current 1200. i've still got some more slack to back it off, but only about 1 mm more until it would be flush with the TB housing.

so could it just be the new cleaner throttle body? i mean, this thing was so gunked up there wasn't any room for air to get through when the butterflies were closed, now there's a .5 mm all around.

btw, it's a 97 z28.

thanks.

 

Doesn't seem a super clean tb & slp cai should give 1200rpms. My m6 idles ~900
Cleaning the tb may have pushed gunk into your recently replaced iac or the pintle may be misadjusted. Otherewise I'd check for leaks in the cai & maf connections.

my guesses, Brian

 

Did you forget to plug something back in, or maybe broke something by accident or without knowing. Is the TPS sensor in tact? Just check everything all over again. Another option is to replace your factory intake and see if it makes a difference, although I doubt it will. I can't imagine just a clean TB would make your car do that. Go to autozone and see what made the SES light come on, that might point to it. They will scan for free.

 

Is the TB to intake manifold gasket in properly? Did you reconnect the vacuum line for the EEC purge solenoid? Is the cable allowing the blades to close fully? Did you disassemble the bottom plate from the TB to clean it? If so, is the plate on tight with the gasket in correctly? Did you put the foam seal back in the TPS sensor?

You are getting air into the engine from somewhere other than the IAC passages.... you need to find the leak.

 

thanks for all the advice, i'll go over it and check for any leaks, i'm pretty sure i put all the connections back securely and the throttle body - intake gasket on right. i've taken it off before (to replace the IAC) and put it back the exact same way...

if i figure it out, i'll let you know what the problem was.

 

you might want to try getting a hold of a stock TB and seeing if that solves your prob. if so then you screwed up ur TB when you cleaned it.

 

well, i went over and checked all the connections. they all seem fine.

i've taken the TB off about 4 times and only replaced the gasket the first time, (because it crumbled).

could it be the re-torquing multiple times? causing a little bit of a leak?

i guess i'm just gonna wait til the SES light comes on again and take it to autozone.

 

Are you sure the intake elbow isn't torn or maybe it is not completely on the TB?

 

it just decided to work properly now.

i dont know what was wrong....but now it's idling fine.
atleast i'm assuming it's fine, it idles at about 900, maybe 875 or so, when it's completly warmed up, and in park. this is normal right?

about 600 or so in drive. is that good?

 

Its the PCM learning the airflow or somthing. Mine did the same exact thing. It also just died on me, when I was driving. Did it on 3 occasions, each times I installed/uninstalled the CAI.

But its normal dude. I would worry If I were you.

 

Check this closely with a mirror if you can. It is very common for the underside to "fold" under and you'll experience a vacuum leak here if this happens. I've seen it on several cars so check this one good!

 

you would worry? or wouldn't?

well, like i said it's gone now. just fixed itself.
what i don't understand, is if the PCM has to learn it, how come when i unplugged the PCM fuse, and put it back, it didn't reset itself and learn right away. it still took a few miles.

and i did check the under elbow , i actually bought a telescopic mirror from autozone for that purpose the other day....that and changing my window motor.

anyways. thanks for all your help.

 

i think i've read somewhere on the board that it takes 5-10min of constant idling for the pcm to re-learn, maybe that was it

 

I'm almost certain its the TPS sensor if the SES came on, you can buy a new one at pep boys or wereever for like 26 dollars, I work at a fuel injection shop and its a porb with all gm TPS's once you take them off they dont go back on right. I also had the same problem when i cleaned my Throttle Body, SES showed .004 at the TPS and normal is .4- .6 i believe at idle.