evo462

iTrader: (27)

I just installed a stock LS1 P&P TB on my 2002 Z28. The install went fine but when I started it up and took it for a test drive, I noticed that it idled unusually high and after I revved it, it took longer than normal for it to "come down". It's idling around 1100+ RPM right now, normally it's around 8-900 RPM and returns to idle quickly after a rev.

I adjusted the "post" that the throttle arm rests on the throttle body housing and lowered it to where part of one thread was showing, similar to my original TB. When I rev it, it'll kind of hang around 1600 RPM for about 3 seconds, then quickly drop to 1100 RPM.

It's like the car thinks the throttle position is slightly open, and it's not idling right. There's a SES light which I haven't checked, but it came on earlier today prior for the EVAP system (PO400) so it's possible that is what its on for again.

Thoughts?

kmracer

iTrader: (1)

with the car running, tap the brake pedal rapidly 4-5 times. if you notice the idle jump, its a vacuum leak.

did you change anything else?

evo462

iTrader: (27)

thanks for the reply! nope...didnt jump up. same thing as before

Mart00SS

iTrader: (19)

Post a pic of the throttle blade closed. Its possible that whoever ported it took too much material off the side of the housing causing a leak between the blade and the housing.

evo462

iTrader: (27)

I'll have to pull it off in order to do that...which I might have to do if I can't get this worked out anyway. It looked like a tight fit to me.

eseibel67

iTrader: (10)

I made this mistake. It doesn't take much to make the hole too big for the blade.

Luckily, plugging the bypass hole in the blade cured it.

evo462

iTrader: (27)

What did you plug it with? A weld?

WS6nJAX

iTrader: (207)

plugging/covering the idle air hole is possibly a band-aid and not a fix. there are a couple other things that you can try prior to that. the are you sure you reinstalled the the o-ring on the iac sensor? do you know how to do a manual re-learn with the tps??

masterz28

iTrader: (8)

whats a manual relearn?

evo462

iTrader: (27)

Well I did disconnect the negative battery terminal for about 15 minutes if that's what you're referring to.

WS6nJAX

iTrader: (207)

the way i always suggest it be done is as follows...

with the key off, unplug the tps / throttle position sensor
turn the key on / forward in the on position for 10-15 sec
turn the key off
reconnect the sensor, start her up and see how she acts

still tho, double check the o-ring for proper install and damage.

Mart00SS

iTrader: (19)

All you have to do is take the lid and bellow off and take a picture.

like this

raidernation3017

iTrader: (1)

I had the same problem and the manual relearn worked for me

evo462

iTrader: (27)

You're right...all I have to do is remove the air intake haha. Anyway, here it is. The TB looks straight and the seller was great to deal with, so I am certainly not trying to slight them.

WS6nJAX

iTrader: (207)

the idle air hole is drilled larger than stock. thats most likely the problem.

evo462

iTrader: (27)

Just tried it - it *might* idle 50 RPM lower but it's still sitting at 950 RPM idle and still does the "hang" after a rev around 1500 RPM, then rapidly drops to idle.

I dunno. Maybe the TPS or IAC is crapped out and my fondling it during the swap finally made it go kaput. I guess I can have O'Reilly's scan it tomorrow and see if it pulls up anything suspicious.

WS6nJAX

iTrader: (207)

nothing i suggested is gonna work. the idle air hole is WAY larger than stock my friend.

evo462

iTrader: (27)

I guess my untrained eye didn't even notice. Thank you for your input.

I certainly don't feel comfortable putting a bolt through that hole so I guess I'll just take the TB off.

*edit*

I just went out and tried covering up the hole...yep...idled like normal with just the smallest amount of the hole covered up. After comparing the two, the ported TB's hole is a tiny bit bigger which I guess makes all the difference. It's too bad it won't work for me, it felt great at WOT.

Mart00SS

iTrader: (19)

hes right. THe idle hole is drilled out bigger than stock. Also I cant tell if the top of the blade might not be making a nice seal or it could be a shadow.

evo462

iTrader: (27)

I couldn't tell at first until I looked at the "grid" made by the lines etched into the blade and the hole does look bigger.

I'm going to swap my stock blade back on and see what happens.

Thanks for everyone's help!