Fitech IAC Steps Issue

[ChrisC74]

I played with making some adjustments to my Fitech system today. Overall I am happy with the way it is running right now but I think it can be better.

I keep seeing that the IAC steps need to be set between 6 and 10 for it to run properly. After it is warmed up I can get the idle set at 850 and the IAC around 8 or 10. This is done by making minor adjustments of the front and back adjustment screws on the throttle body and turning the truck off after each adjustment to let it recalibrate the TPS, etc.

The problem comes when I go drive it. I let off the gas and it drops to zero or one. It only rarely settles back to the eight to ten setting.

I can not figure out why it will not hold this setting. I get home, let it sit for fifteen or twenty minutes fire it up and it is back where it should be.

I am fighting a strong exhaust stink when I come to a stop or quick decel. On the few times the setting has stayed the smell was not there.

Anyone watch their IAC while they drive? Does your IAC number always return to the proper set point when you stop at a light or stop sign?

Thx,
Chris C74

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[.94 OR]

Mine has been showing 16. I also get the stink especially when I get home and let it idle in garage for a moment before I shut it off.

Any luck with the Logging feature? I was hoping to get a readout on mine so I could visualize what it is doing on paper.

 

[ChrisC74]

I have not tried logging. I will give it a try this week. So are you setting it in the 6 to 10 range and it is creeping up to 16 or are you steady on 16.

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[.94 OR]

I haven't set it, but it fluctuates and I have seen 16 at different times. That is one reason I was hoping for a read out so I could identify when these things are happening since the screen will only show so many parameters at a time.

 

[ChrisC74]

I haven't set it, but it fluctuates and I have seen 16 at different times. That is one reason I was hoping for a read out so I could identify when these things are happening since the screen will only show so many parameters at a time.

Setting the IAC steps is one of the first things you need to do out of the box. The thing that I have found is that you want to make very small changes and only change one thing at a time. If you try to make multiple changes at the same time then you will be forever chasing your tail.

If the idle is where you want it them make small adjustments - like a quarter turn or less on the back adjustment screw - to adjust the numbers down you need to open the throttle blades. Make a small adjustment, turn off the truck, let the screen blank out and then restart. This will reset everything to the new setting.

This is one of the first things they will have you set if you call them for trouble shooting.

 

[ChrisC74]

I talked to FITECH and all they came back with was that it is AFR related. So i am going to play with those settings tonight.

I would really appreciate it if someone here who is running the Fitech could take their truck for a spin and watch the following. What are your IAC steps doing at startup? What are they doing once the system has reached operating temperature. And the big one - if you stop at a stop light, stop sign, dump the clutch, etc. do your IAC steps drop to 0? Do they say close to the original setting? If they drop to 0 how long does it take to recover to your proper setting of 6 to 10?

Thx,
Chris

 

[JWMcCrary]

First, I have no experience with Fitech, but I will pass along my experience with similar on the Holley Terminator.

I was having the same thing happen after full temp and driving, IAC would be 0. I set mine to be 3 to 5 warmed up idling and backed off the throttle blades an additional 1/4 turn, since then it has stayed 1 or above but under 10 after driving. Hope that helps you, both systems probably use same IAC motor.

 

[ChrisC74]

First, I have no experience with Fitech, but I will pass along my experience with similar on the Holley Terminator.

I was having the same thing happen after full temp and driving, IAC would be 0. I set mine to be 3 to 5 warmed up idling and backed off the throttle blades an additional 1/4 turn, since then it has stayed 1 or above but under 10 after driving. Hope that helps you, both systems probably use same IAC motor.

Thanks - make sense. I will give it a try.

 

[.94 OR]

Setting the IAC steps is one of the first things you need to do out of the box.

How was I to know this was the first things to do? I read what was available and am still scratching my head on steps to tune this thing besides driving it for 300 miles and letting it self learn.

If my hot and cold start were better I wouldn't mind driving it somewhere, shutting it off, then coming back but I have had a couple times when it wouldn't re-start hot so I only make laps back to the house with mine so far.

 

[ChrisC74]

How was I to know this was the first things to do? I read what was available and am still scratching my head on steps to tune this thing besides driving it for 300 miles and letting it self learn.

If my hot and cold start were better I wouldn't mind driving it somewhere, shutting it off, then coming back but I have had a couple times when it wouldn't re-start hot so I only make laps back to the house with mine so far.

I understand your frustration. I think this is a good system but the written documentation is terrible. Add to that you can call their tech line and get different answers to the same question depending on who you talk to.

There are several good tech forum write ups on this system. If you google Chevelle Fitech Tips you will come to their forum. It is up to about 68 pages now of back and forth, tech tips, etc. they welcome all Fitech users - there are folks with mustangs, etc. all commenting and helping each other.

Supposedly Fitech is going to start a forum and is working on a better manual but i would not hold my breath.

Can you post up some info on what you have - which Fitech, what engine, trans, ignition, etc. and maybe we can help.

I took out my Howell TBI and went with this system b/c I wanted to be able to make changes and tweaks myself. It is a little overwhelming but even with my issues my truck is running better than it ever has.

-Chris

 

[bannind]

Chris - any progress on the smell during hard stop/decell?

 

[ChrisC74]

Chris - any progress on the smell during hard stop/decell?

I played with it a little today. Since my software was a year old Fitech sent me the new version. I loaded it this morning and have to start over with the settings from scratch.

I also properly adjusted the IAC steps from the front and then adjusted the rear screw to just touch the blade.

Drove for a bit and I think it is a little better. Tomorrow I am going to go back in and put in all of the decel suggestions and see what happens.

I can tell you that by accident today I put the truck in neutral coming up to a stop and slowed to a stop with just brakes and had NO SMELL. Then on the way home I have a long down hill that slows to 25 mph and has some quick curves. This is a place where I would always down shift from third, to second and let the engine slow me down. It was a consistent place for me to get a good dose of the smell and sometimes popping like it was lean. Today, at the top at about 40 mph I put the truck in neutral coasted down the hill applying brakes where I needed to down to about 15 mph and NO SMELL, NO POPPING. I did this twice, no smell and then a third tim with downshifting and had the smell.

So I am pretty sure with all of the standard and pro tune settings on this thing that I can turn it out. It is just going to take time.

I will try some more tomorrow.


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[ChrisC74]

Chris - any progress on the smell during hard stop/decell?

Bannind - just to follow up I got a reply on the Chevelle forum - a guy over there is running a NV3500 trans (I have an NV3550) and he is getting the same stink. He said he was told to adjust the DFCO but he has not done that yet - he said he just throws it in neutral and coasts.

So obviously it has some thing to do with the fuel cutoff when downshifting and off throttle...

I will circle back with you once I try to make some adjustments.

-Chris

 

[Digger556]

I don't own an FItech unit, but I do have a TBI megasquirt setup. I strongly suspect you are are experiencing the typical enrichment that occurs when the throttle is shut at high rpm. (Anything above idle) This is what I'm dinking with on my setup right now.

I don't know if the FItech unit has an equivalent, but the Megasquirt/Tunerstudio software has settings for what is called Enhanced Acceleration Enrichment or more commonly known as X-Tau. Basically it's a set of features that help account for the film of fuel that accumulates on the walls of the intake manifold.

Right now I suspect that as you shut the throttle, the pressure in the manifold drops quickly and the accumulated fuel is evaporating and adding to the fuel already being pumped into the cylinders until the wall film reaches equilibrium again. Thus making the mixture rich and stinky.

You could help the situation by cutting fuel more aggressively on decel. The proper solution is for the computer to scale back fuel under falling rpm/manifold pressure situations so the total fuel being fed into the cylinders remains balanced.

 

[ChrisC74]

I don't own an FItech unit, but I do have a TBI megasquirt setup. I strongly suspect you are are experiencing the typical enrichment that occurs when the throttle is shut at high rpm. (Anything above idle) This is what I'm dinking with on my setup right now.

I don't know if the FItech unit has an equivalent, but the Megasquirt/Tunerstudio software has settings for what is called Enhanced Acceleration Enrichment or more commonly known as X-Tau. Basically it's a set of features that help account for the film of fuel that accumulates on the walls of the intake manifold.

Right now I suspect that as you shut the throttle, the pressure in the manifold drops quickly and the accumulated fuel is evaporating and adding to the fuel already being pumped into the cylinders until the wall film reaches equilibrium again. Thus making the mixture rich and stinky.

You could help the situation by cutting fuel more aggressively on decel. The proper solution is for the computer to scale back fuel under falling rpm/manifold pressure situations so the total fuel being fed into the cylinders remains balanced.

Thanks Digger. I think you are exactly right. There are some basic tuning settings available like decel fuel cutoff, etc. if it needs to get deeper than that the unit can with some protuner software but it is probably over my head. I am going to try to work with what I can for now and then see if I need to dig deeper.

Thanks again,
Chris

 

[ChrisC74]

Here is an answer to my post asking about the fuel stink on decel over on the Chevelle forum.

I will not have time to test any of this until closer to the weekend but looks like good, specific suggestions on where to adjust.

-Chris

QUOTE=prj daily driver;9120458]Chris C74,

Try this below.

The popping may never go away - mine was so bad I wanted to go back to the carb. But perseverance pays off and I have very little popping now. It still pops a little but rarely. The throttle body does keep adapting and learning. I have over 700 miles on mine now and it's manners keep improving.
Your decel setting at -36 is good. You can bring it lower, more minus, but -49 is probably too low. I tried mine at -69 but now it is set at -35.

Bring the Loop Rate Up to 30-35 start by trying 33 and see where this takes you. As well, in Idle Control in the Pro-Tuning section go down to Decel RPM decay and Decel IAC decay. These settings are a ratio - if you go up 3 numbers on top then it's only 1 value number for the IAC below it. The RPM range is 0-15 and the IAC range is .1-.9. My settings are 9.4 on top value and .6 for the bottom value. Don't be scared to play with the lower setting. Try going 1 value higher or lower on the Decel IAC decay. You should see the rpm value move better to stabilize idle. This will take some time and experimentation. By balancing the Loop rate up/down and the Decay RPM/IAC your idle should even up.[/QUOTE]

 

[bannind]

Chris,

Thank you for keeping this updated. I know it will be a huge help to myself when I get the time (and money) to convert to EFI.

Thanks,
dan

 

[ChrisC74]

Chris,

Thank you for keeping this updated. I know it will be a huge help to myself when I get the time (and money) to convert to EFI.

Thanks,
dan

No problem. I figured you were fighting the same problem.

I will keep it updated on what works and does not work for me.



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