Ported TB - high rev on startup?
Thread Starter
Pro
Joined: Jun 2000
Posts: 572
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From: kansas city KS
Ported TB - high rev on startup?
I installed ported TB over the weekend, have started and drove the car a couple of times.
When I start the car now it initially revs really high. Within a couple of seconds, it settles down to normal level and idles smooth. It's been bad weather around here so haven't gotten on it - but it drives just fine after the initial rev.
Is this typical - thoughts on cause? I'm not liking the high rev on initial startup w/no oil pressre...
thanks,
Cliff
Melting Slicks
Joined: May 2003
Posts: 2,851
Likes: 1
From: San Bruno Ca
Re: Ported TB - high rev on startup? (cliffkh)
The high idle syndrome happened to my car also, but after a drving it a few times it went away. No doubt the computer adjusted itself to the newly ported TB.
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Team Owner
Joined: Sep 2001
Posts: 23,283
Likes: 906
From: Lake Elsinore, CA
Re: Ported TB - high rev on startup? (cliffkh)
The PCM may eventually adjust but it can be fixed immediately through tuning. A buddy and I had the same issue with our h/c and ported TB and tuned it out using LS1 Edit. We didn't want to wait the number of cycles it might have taken to let the computer learn and log all those low pressure/high rpm starts.
Instructor
Joined: Sep 2003
Posts: 104
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Re: Ported TB - high rev on startup? (cliffkh)
You might try the idle relearn procedure. Otherwise it may get better with some more running time. Search or ask your TB porter for the procedure.
With an A4 Vette especially, final idle speed can be effected by porting. My A4 has porting specifically for A4 and it idles at 550-600. If I put a TB ported for an M6 on it, the idle goes up a little and the A4 car creeps a lot more at a light. I didn't like this, so I changed to the "A4 porting". It's not from a sponsor on this board.
With an A4 Vette especially, final idle speed can be effected by porting. My A4 has porting specifically for A4 and it idles at 550-600. If I put a TB ported for an M6 on it, the idle goes up a little and the A4 car creeps a lot more at a light. I didn't like this, so I changed to the "A4 porting". It's not from a sponsor on this board.
Thread Starter
Pro
Joined: Jun 2000
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From: kansas city KS
Re: Ported TB - high rev on startup? (cliffkh)
thanks to all for the replies -
re: LS1 edit tuning - I have access to edit - what tables do I need to look at? Is there a documented procedure for idle tuning? thanks.
re: LS1 edit tuning - I have access to edit - what tables do I need to look at? Is there a documented procedure for idle tuning? thanks.
Drifting
Joined: Aug 1999
Posts: 1,278
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From: Amelia ohio
Re: Ported TB - high rev on startup? (cliffkh)
thanks to all for the replies -
re: LS1 edit tuning - I have access to edit - what tables do I need to look at? Is there a documented procedure for idle tuning? thanks.
re: LS1 edit tuning - I have access to edit - what tables do I need to look at? Is there a documented procedure for idle tuning? thanks.
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Instructor
Joined: Sep 2003
Posts: 145
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From: Scottsdale Arizona
Re: Ported TB - high rev on startup? (cliffkh)
Start by reducing the IAC park position from 310 down to about 250. See if this helps. Depends on how much porting was done. You may have to go to the park position values and reduce those as well. Whats happeming is that more air is coming in and the PCM takes a few seconds to close the throttle blade to reach the desired idle speed.
Melting Slicks
Joined: Feb 2002
Posts: 2,613
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From: Winston Salem NC
Re: Ported TB - high rev on startup? (goodhands)
Pre A4 porting for TB's I tried lowering the "Reset IAC" from 310 to 250 and it made no difference. I just read the Edit description and it says it's the default value after a power reset of the PCM. Has anyone lowered the value and disconnected the battery? I did not and maybe that's why it didn't work for me. I have the A4 throttle body from Bauer and it works great with stock values. All that needed changing were the idle settings. I'm curious about if disconnecting the battery helps. As goodhands points out, lowering Park Position table values works too. Lower those in small increments, like .05 at a time. If you go too far it will cause the car to stall at startup. Just raise them some then.
Thread Starter
Pro
Joined: Jun 2000
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From: kansas city KS
Re: Ported TB - high rev on startup? (2C5only21)
good question - on most h/c + full bolt on cars it is often 5-8 rwhp per my research. Also depends on quality of the port job - it can do more harm than good. I've seen everything from 0 to 12 posted.