C5 idle problem/question
Thread Starter
Cruising
Joined: Feb 2009
Posts: 12
Likes: 0
From: Olympia WA
C5 idle problem/question
I have a '99 FRC (6-speed), it's stock other than the Blackwing air intake. The issue I'm having is that when I come to a stop while driving, the idle hangs at about 1500rpm for 5-10 seconds before it falls back to the normal 800rpm or so. It's more of an annoyance than anything else, but I don't think it should be doing it. I'm thinking maybe the throttle body needs cleaned, or maybe a small vacuum leak - has anyone had this problem before? Back in 2000 I bought a new Firebird with the LS1 and 6-speed. With about 20,000 miles it started occassionaly doing the same thing but I turned it back in on the lease without ever fixing it - is this a common LS1 thing? Thanks for any information that could be shared with me.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Take a look at the PCV valve to the intake connection tube. They can and will develop a hole on the bottom of it sort of out of sight yet cause some problems like this. You may also need to do an Idle Relearn.
Thread Starter
Cruising
Joined: Feb 2009
Posts: 12
Likes: 0
From: Olympia WA
I noticed in another post someone said they had purchased a ported throttle body and it had a hole drilled in the butterfly....everyone is saying that is not stock and really not needed, someone also mentioned that could make the idle hang, like mine is doing - when I looked at the throttle body today I noticed it had a hole in the butterfly, I assumed that was a stock configuration, maybe I need to plug that hole and see what happens.
Team Owner
Joined: May 2001
Posts: 36,836
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From: Dear Karma, I have a list of people you missed.
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16
I noticed in another post someone said they had purchased a ported throttle body and it had a hole drilled in the butterfly....everyone is saying that is not stock and really not needed, someone also mentioned that could make the idle hang, like mine is doing - when I looked at the throttle body today I noticed it had a hole in the butterfly, I assumed that was a stock configuration, maybe I need to plug that hole and see what happens.
If you don't find anything obvious, find a GOOD tuner to look into this. When my '99 was stock with bolt-ons only (Blackwing, headers and Z06 intake) it did not do this.
Drifting
Joined: Mar 2005
Posts: 1,737
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From: Northern VA
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Burning Brakes
Joined: Mar 2003
Posts: 1,156
Likes: 2
From: Arlington VA
As previously posted, sounds like unmetered air entering the intake. Check all the couplers and connections coming from your Blackwing to the TB and make sure the are straight and tight. Check the back of the Intake manifold and see if one of the vaccuum lines has become disconnected. Good Luck.
Thread Starter
Cruising
Joined: Feb 2009
Posts: 12
Likes: 0
From: Olympia WA
Thanks for everyones advice - I ended up removing the throttle blade and had the hole welded up and then also replaced the PCV valve with a different one that allowed me to just run 3/8 hose from the plastic line to the throttle body, eliminating the original rubber boot that held the pcv valve(the boot didn't seem to have a very good seal to the pcv valve). It seems to have taken care of the idle hanging at stops, I will say that the car did idle a bit smoother with that hole in the throttle blade though.