Wondering if someone can help.

I have a 406 SBC with the Accel Gen 7 setup and a Pro Ram single plane with a 4 barrel throttle body.

The car runs pretty good, made good power, but I've never been able to solve an IAC issue it had. I cannot get the IAC value below 20 in the target idle screen. I check it when hot, and the Accel instructions say that opening the throttle blades lowers the IAC value. Whats odd is that it seems to act the opposite of that. This engine always needed a ton of idle air with a carb, so I wonder if that is affecting whats happening here. I've heard talk of drilling throttle blades, but want to make sure its just not me thats doing something wrong before drilling. I've also always opened the secondary throttle blades on Holleys to get more idle air instead of drilling and it worked well also.

So should the IAC values change "real time" as I adjust the throttle blades? Or is there more to it? It seems somewhat unresponsive when adjusting.

Sorry for rambling, just hoping to dial in the last couple quirks I have. Thanks for any thoughts!

 

I've had my Accel Pro-Ram and their 1200 CFM 4 barrel TB over four yrs now with no issues. Are you using an Accel TB? If so you should be able to adjust your secondaries because they all have progressive links just like your holley. Then you should see your IAC counts going down. But if your trying to adjust them the way Accel said too, you will need to reset your TPS voltage as well.

 

Yup, I'm running the Accel 1200 TB also.

So are you saying that I need to reset the TPS every time I make a small adjustment on the primary throttle blades to see the IAC change on the laptop? What are your IAC values? I'm wondering also if mine are just gonna need to be higher than Accels 5-8 recommendation because of the cam being a bit choppy.

Maybe it would work out best to open the secondaries a bit to get a rough adjustment, then fine tune with the primary side. Pulling off the TB to adjust the secondaries every time would be a pain in the butt.

 

Thought about it a little more and I now understand that the low TPS will need to be reset every time even a small adjustment is made at the throttle blades(primary only). That way the ECM sees it as a closed throttle (idle) position again rather than open throttle. Will the TPS reset affect the IAC value?

 

I don't know about pulling the TB to make adjustments to the secondaries. My TB is 5 yrs old and it has an allen screw on the secondary to make adjustments for fine tuning you may have a later model TB than I do. To answer your question about how many IAC counts I have? I have 0 counts at idle, but when in gear it's about 5-10 because you have a load on the motor and it's working against your convertor. That's where it needs to, but make sure you give the motor what it wants to run smoothly not what you think it wants. So get to tuning. By your TPS volts will increase if your making your adjustments with primary there for your iac counts will rise as well that's why you need to reset them to .56 to .60.

 

Messed around with it some tonight and made a little progress. Opened the secondary blades a bit (gotta pull the TB on this one), and when I fired it up it was right at 5 for IAC counts. Problem is that it was idling at 1600 RPMs. Closing the primary blades to get the idle down drove the IAC back up to 13 though. Reset the TPS at .57 after it all also. Little confused how to correct that.

Its surging bad in gear again now and the idle isnt very consistent. Gonna have to go back to the drawing board a bit here. Any tips?

 

If that's the case then reset the secondaries because if you have to remove the TB to make an adjustment then it's not worth the time or trouble just start from scratch. The reason why your car is surging because you are adjusting the primary blades in conjunction with the TPS to achieve .57 volts. The TPS needs to be adjusted by itself.


The process is too adjust the primary first and then reset the TPS volts to .57 by loosening the two screws on the side of the TPS, when doing this make sure the ignition is in the ON position and the car in not running. Once complete return the ignition to the off position wait a few seconds and start the car. You will repeat the the process until you have reached the desired Idle RPM / IAC counts with the car in gear and without idle surge. If done correctly all the surge should be gone. And that's what I meant when I said to give the car what it wants not what you think it's wants. Good luck!

 

I'm a little confused now. Maybe I wasnt very clear in how things were going.

Are you referring to the TPS when you say IAC? As in adjustment?

The method I originally tried to use was adjust the primary throttle blades to lower the IAC numbers, then afterwards would reset the TPS voltage and record the low TPS setpoint in the DFI.

Is that correct?

 

Yes. Oh my goodness, I can't believe I just posted all that info to tell to adjust your IAC. I know you were scratching your head. My bad man!!! I'll fix my post. But yes that's what I was referring too. I was up late that night before installing a LT4 hot cam in a 94 z28, headers, and a stall. So I was pretty tired after work.

 

I'm an Accel EMIC, if I may, you can't shoot for a specific TPS value, they're all not calibrated the same.

Open the primaries a little at a time. After each adjustment go to "Calibrate TPS", then reset low setpoint. Just make sure it's over .5. Then go to "Idle Configuration", make sure you have about 1-2% in the TPS settings, otherwise it will either try to stay in idle mode too far into the throttle (might be causing your surging) or won't have enough range to stay in idle mode after small adjustments.

Then if your idle is O.K. but still somewhat unstable go to "Idle spark compensation" and play with those advance/retard settings.

Also check to see that your Acceleration threshold is set high enough that it's not try to add fuel during idle.

I've found that if you have a bigger cam a lower IAC number is beneficial. Remember it's trying to respond to airflow changes that have already happened. I usually set the IAC low and stabilize the idle with the "idle spark compensation".

Email me your cal if you want
fastone01@hotmail.com

It's still the best system on the market imo. Anyone else hold patents like they do? Nope.

 

Thanks for the responses, and sorry for the delay.

I actually solved a little bit by finding and understanding the start up term. It was set for +13* at 190* coolant, so it was adding a ton of timing when trying to restart when hot. My timing curve is pretty agressive, so I flipped it to -10* and it helped.

One question though, I did more reading again in the manual tonight and think I had something mixed up. When restarting hot sometimes, it acts flooded, so I have the starting fuel coefficient almost bottomed out. I always though the after start coeff. VS. ect was related to decay, but now I dont believe so. Is the starting coeff. strictly while the engine is cranking, and the after start coeff. the absolute second it fires? I'll play with it tomorrow, but maybe I need to just try taking a big whack out of the after start and try that. When it acts up starting hot it'll fire, then huff a couple times and die. I need to hold it wide open to refire. Refires almost instantly and idles perfect again.

EFIguy, I will certainly send you my calibration to check out if it isnt too much trouble. I'll follow your directions for setting the IAC tomorrow and see how it works.

One last thing, I cannot find it anywhere in my manual. What are the IAC feedfwd counts in the idle configuration page?

 

Try control C.