HP Tuner Question about IAC
Thread Starter
TECH Fanatic
iTrader: (15)
Joined: Jul 2002
Posts: 1,441
Likes: 1
From: Shelby Twp. Mich
HP Tuner Question about IAC Ok ,I have now got my Car starting great thanks to you guys and especially Billiumss 
Ok Now when car Gets warmed up 10 to 15 minutes of driving and it starts surging like crazy at a stop light
Do I play with Idle Airflow vs. coolant Temp vs. (Gear & PN)? Now How do I experiment with these numbers?Do I go Higher or lower?Maybe If I change the the numbers in gear at said Temps I could fix this problem? I just dont know which direction to go 
Thanks alot for all the Help...
Scott
Ok Now when car Gets warmed up 10 to 15 minutes of driving and it starts surging like crazy at a stop light Do I play with Idle Airflow vs. coolant Temp vs. (Gear & PN)? Now How do I experiment with these numbers?Do I go Higher or lower?Maybe If I change the the numbers in gear at said Temps I could fix this problem? I just dont know which direction to go Thanks alot for all the Help...
Scott
What are your IAC counts at? If they're too high, fix that first by opening the throttle more. If they're not you could add a little to the throttle cracker at the speed it's happening at.
After reading gameover's posts on IAC trims, it really isn't a big deal what you set the idle air flow at because it will change to maintain your idle rpm and remember the iac position it took to maintain that rpm. What I would do is look at your MAF readings at idle and put that number in the warm settings for your idle air cells. The reason is if you ever unhook your battery or something your car won't run like complete **** while it relearns the iac trims.
After reading gameover's posts on IAC trims, it really isn't a big deal what you set the idle air flow at because it will change to maintain your idle rpm and remember the iac position it took to maintain that rpm. What I would do is look at your MAF readings at idle and put that number in the warm settings for your idle air cells. The reason is if you ever unhook your battery or something your car won't run like complete **** while it relearns the iac trims.
The numbers I listed were IAC counts (or steps), you can get those by logging. IAC counts just let you know how far the iac is open. I think the 15 you're talking about is your idle airflow in grams per second. My warm idle airflows are set at like 7.3 grams per second.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
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
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Originally Posted by marc_w
FWIW, my surging is always associated with VE changes.
TECH Addict
Joined: Oct 2003
Posts: 2,620
Likes: 0
From: Central, MA
That's strange... Like I said in a few other posts around here, my truck runs the best off of a stock VE table. If I scale down the 400-800 columns more than 95% or so, I get nasty surging and stalling. It seems very sensitive to changes.
TECH Regular
Joined: Apr 2003
Posts: 413
Likes: 0
From: Atlanta, GA
Originally Posted by Pro Mouse
Hmmm ,so making changes can cause surging?Will it learn it out?
He's right about the surging or stalling in reference to the VE table, Not all cars can use the scale back by a percentage procedure posted on this forum. My car for instance ran very lean @ startup so I had to increase the lower VE tables to get it richened up enough to run correctly. When it would stall/surge it the A/F ratio was around 16.5 and it would clear up when the PCM adjusted it back down to 14.7-15.0
TECH Addict
Joined: Feb 2004
Posts: 2,826
Likes: 0
Originally Posted by monodax
He's right about the surging or stalling in reference to the VE table, Not all cars can use the scale back by a percentage procedure posted on this forum. My car for instance ran very lean @ startup so I had to increase the lower VE tables to get it richened up enough to run correctly. When it would stall/surge it the A/F ratio was around 16.5 and it would clear up when the PCM adjusted it back down to 14.7-15.0
TECH Regular
Joined: Apr 2003
Posts: 413
Likes: 0
From: Atlanta, GA
Originally Posted by Another_User
Soooo...why cars run better with an accurate VE table actually comes down to being within the 25% swing window for trims, and the closer the better because it gurantees faster "converge" times for any driving condition?
This is also more pronounced @ lower RPM ranges. If the RPM range is < 2400 RPM the PCM weights the Speed Density Calcs (VE Table) higher than it does the MAF input. So you would see more driveability issues with a VE table that is not as accurate @ Low RPM ranges. As the RPM increases the PCM uses the VE table more as a sanity check as the MAF sensor is more accurate @ higher RPM ranges.
TECH Addict
Joined: Oct 2003
Posts: 2,620
Likes: 0
From: Central, MA
Okay... I was running on what I thought was a "good" tune yesterday, and out of the blue I had surging and stalling problems. I also had bad cruise control effect.
My "good" tune, was my stock VE table. Any change I made seemed to effect the idle after about 45 minutes of driving.
I was driving on my stock VE for 75 miles at the time that this started to happen. About the longest I ran a single tune for since I dropped the cam in last weekend.
I went ahead with the common cam recommendation, and hit my lower VE table by 70, 80 and 90 percent. I reset my fuel trims, and then did an idle-relearn (I think). I did this by pulling a few ECM/VCM fuses, flicking the key on and off, inserting fuses, and letting the engine idle for 10 minutes, idle with AC on for 5, and then idle with AC off for another 5. I drove about 200 miles after that, and never once had any surging or stalling problems.
Previously running these same VE specs, I ran into trouble.... So my theory right now is that and idle relearn or fuel trim reset is needed after making VE changes...
My "good" tune, was my stock VE table. Any change I made seemed to effect the idle after about 45 minutes of driving.
I was driving on my stock VE for 75 miles at the time that this started to happen. About the longest I ran a single tune for since I dropped the cam in last weekend.
I went ahead with the common cam recommendation, and hit my lower VE table by 70, 80 and 90 percent. I reset my fuel trims, and then did an idle-relearn (I think). I did this by pulling a few ECM/VCM fuses, flicking the key on and off, inserting fuses, and letting the engine idle for 10 minutes, idle with AC on for 5, and then idle with AC off for another 5. I drove about 200 miles after that, and never once had any surging or stalling problems.
Previously running these same VE specs, I ran into trouble.... So my theory right now is that and idle relearn or fuel trim reset is needed after making VE changes...
TECH Fanatic
Joined: Mar 2003
Posts: 1,839
Likes: 0
From: La Porte, TX
Originally Posted by marc_w
Okay... I was running on what I thought was a "good" tune yesterday, and out of the blue I had surging and stalling problems. I also had bad cruise control effect.
My "good" tune, was my stock VE table. Any change I made seemed to effect the idle after about 45 minutes of driving.
I was driving on my stock VE for 75 miles at the time that this started to happen. About the longest I ran a single tune for since I dropped the cam in last weekend.
I went ahead with the common cam recommendation, and hit my lower VE table by 70, 80 and 90 percent. I reset my fuel trims, and then did an idle-relearn (I think). I did this by pulling a few ECM/VCM fuses, flicking the key on and off, inserting fuses, and letting the engine idle for 10 minutes, idle with AC on for 5, and then idle with AC off for another 5. I drove about 200 miles after that, and never once had any surging or stalling problems.
Previously running these same VE specs, I ran into trouble.... So my theory right now is that and idle relearn or fuel trim reset is needed after making VE changes...
My "good" tune, was my stock VE table. Any change I made seemed to effect the idle after about 45 minutes of driving.
I was driving on my stock VE for 75 miles at the time that this started to happen. About the longest I ran a single tune for since I dropped the cam in last weekend.
I went ahead with the common cam recommendation, and hit my lower VE table by 70, 80 and 90 percent. I reset my fuel trims, and then did an idle-relearn (I think). I did this by pulling a few ECM/VCM fuses, flicking the key on and off, inserting fuses, and letting the engine idle for 10 minutes, idle with AC on for 5, and then idle with AC off for another 5. I drove about 200 miles after that, and never once had any surging or stalling problems.
Previously running these same VE specs, I ran into trouble.... So my theory right now is that and idle relearn or fuel trim reset is needed after making VE changes...
That is correct...or at least a good 50 mile trip.
