tuning for ported tb help needed
tuning for ported tb help needed i just put a ported tb on my truck and can't seem to get rid of the hanging idle and high rev when it starts. when i start it the idle goes to like 1200. when i take my foot off the gas the idle doesn't drop back down as fast as it should. what do i do to adjust it?
I actually just fixed/ am working on fine tuning the fix for this. My problem was that the set screw was set too high, causing the TPS to read higher than it should have at idle, once I adjusted the set screw so that the TPS was back to the idle voltage, and then just adjusted the airflow table. The hanging idle has been almost completely taken care of ... so maybe check your TPS voltage, and see if its alil higher than it should be at idle.
Which tuning program are you using?
Which tuning program are you using?
mine did this but after a few restarts it went away. check out the tps % at idle, its possible the port work went too far back and maybe the iac motor is already closed so it take a while to get down
the voltage is 0.54 or something like that. I'm assuming it's just a bad porting job. I can see daylight around the blade. I'm getting a NW 90mm soon I think so I might just put the stock one back on.
You should only see just a crack of daylight around it if its a cable type. If its a DBW TB then its gonna hang open naturally but should still be pretty tight to the housing on the bottom part of the blade.
it's the cable type and i see just a crack of daylight. i haven't touched the idle screw. i tried to do the tps reset 2 different ways. one was to turn the key on, turn it off, unplug the tps, turn it on, turn it off, plug it back in, turn it on.
the other was to let it idle for 15min in gear with ac off, then turn ac on, then let it idle in gear, then drive. NOPE, neither worked. hmmmmmmmmmmmm
the other was to let it idle for 15min in gear with ac off, then turn ac on, then let it idle in gear, then drive. NOPE, neither worked. hmmmmmmmmmmmm
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo I give up. This is the 3rd ported tb i've tried over the past year or so and they have all done the same thing and i could never figure out how to fix it. One was a Shaner's which is supposed to be awesome. Maybe it's just me.
Originally Posted by Bo White
Yeah, somethings up if thats the case. If you dont mind, you can send it to me and Ill look it over for ya. Does the stocker do fine on it now?
i had the same problem when i drilled the hole in the throttle body plate bigger for it to idle after the cam install.. i drilled a 3/16 hole and i started it up and it idled at 1200 and never dropped down.. i read the tps voltage at idle and it was .9 and i lowered the set screw to .58v.. fixed the problem with that... stil doesnt want to idle right until i drive it around the block, it just hunts and hunts
redsupra's website points out....
If you have a bigger throttle body (FAST 90, or Nick Williams) you want to multiply your Effective Airflow Area by 48%. (put in 1.48, select the whole row, hit 'multiply')
actually, i find that ppl have different opinions on that, everything from multiply, divide, or even 'changes made to this table have no effect'. i don't have one myself to try it out on, so tread carefully. i meant to fix it on my site but haven't around to it.
i don't know what's going on. I keep getting that code and tonight when i tried to get on it from a dead stop, the truck started bucking hard. almost felt like the fuel pump was failling or something but the fuel pressure stayed where it should be. No idea what's going on.
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
Likes: 1
From: Sunny London, UK
You should retune your running air flow table so the engine knows how much air you need at idle.
With a TB that lets more air past you need to reduce the flow. Then the IAC will drop to reduce flow around it and should bring you back in line assuming your TPS is set to zero etc.
Whats you IAC counts at Idle with the new TB? If they are greater than say 10 then you have room to drop them down. Stock is somewhere around 30, if your TB is letting too much air through, then closing the IAC might be enough to sort the problem out. You might also need to mess with the IAC effective area table, but start with the RAF one.
Redhotsupra's website has details and a spreadsheet.
With a TB that lets more air past you need to reduce the flow. Then the IAC will drop to reduce flow around it and should bring you back in line assuming your TPS is set to zero etc.
Whats you IAC counts at Idle with the new TB? If they are greater than say 10 then you have room to drop them down. Stock is somewhere around 30, if your TB is letting too much air through, then closing the IAC might be enough to sort the problem out. You might also need to mess with the IAC effective area table, but start with the RAF one.
Redhotsupra's website has details and a spreadsheet.