IAC Adjustment Procedure

[MCH86GN]

I reset my IAC according to the procedure from GNTTYPE.org and then I got my car up to operating temperature so I could try and adjust the IAC because my idle is too high. I then realized that with the 6.0 TT chip that the engine control at idle is open loop and the adjustment procedure from gnttype.org calls for the engine control to be closed loop. Well, I have open loop idle, so is this procedure still valid as long as the engine is at operating temperature?

1. Warm the engine to normal operating temperature. This is important ... the car needs to be in closed loop.
   
2. Connect scan tool. Verify it's in closed loop.
   
3. Put the car in park and wait a couple seconds for it to settle into a regular idle.

The engine was running fine and had a smooth idle, then the vacuum line popped off the PCV. After that the idle was really rough. I popped the hood and I could hear that there was a vacuum line off so I put the line back on and initially the problem seemed corrected. However, after a drive it was really bad with IAC over 150 in park. I figured the IAC got out of whack and that is why I was trying to reset and adjust it. I may need to check and make sure I have no other vacuum leaks and I will check it out as soon as I can. Although I figured that if I had any other vacuum leaks the IAC would go to 0. Sometimes it is at 0, but it does start incrementing.

 

[turbodave231]

Charles,

Loop status should not matter to get the minimum air rate correct. You do need to get the engine full warmed up. To set minimum air rate:

1. Warm the engine to full operating temps
2. Turn engine off and then turn the key back to ON
3. With the IAC connected, jumper pins A and B at the ALDL.
4. Wait 30 seconds and unplug the IAC
5. Remove the jumper at the ALDL
6. Start the engine
7. Adjust engine RPM to 500-550 in Drive using the throttle stop screw on the throttle body.
8. Shut the engine off and plug the IAC back in.
9. Restart the engine
10. Set TPS to .40-.44 volt or whatever your chip manufacturer specifies

At full operating temps, the IAC counts on a scanmaster or scan tool should be somewhere in the 20-40 count range at idle. The IAC counts go up as you open the throttle (throttle follower function)

If you have a vacuum leak, you may not be able to obtain a low enough idle speed during the above procedure. Air is entering the intake manifold and not going through the throttle body.

 

[MCH86GN]

Charles,

Loop status should not matter to get the minimum air rate correct. You do need to get the engine full warmed up. To set minimum air rate:

1. Warm the engine to full operating temps
2. Turn engine off and then turn the key back to ON
3. With the IAC connected, jumper pins A and B at the ALDL.
4. Wait 30 seconds and unplug the IAC
5. Remove the jumper at the ALDL
6. Start the engine
7. Adjust engine RPM to 500-550 in Drive using the throttle stop screw on the throttle body.
8. Shut the engine off and plug the IAC back in.
9. Restart the engine
10. Set TPS to .40-.44 volt or whatever your chip manufacturer specifies

At full operating temps, the IAC counts on a scanmaster or scan tool should be somewhere in the 20-40 count range at idle. The IAC counts go up as you open the throttle (throttle follower function)


If you have a vacuum leak, you may not be able to obtain a low enough idle speed during the above procedure. Air is entering the intake manifold and not going through the throttle body.

Turbo Dave, thanks for the input. Essentially my question was, would this procedure work in open loop idle. Because the procedure calls for closed loop idle. Believe it or not I worked in Powertrain Engine Engineering at Ford Motor Company for 4 years. I did an abstraction of the engine control software referred to as high-level drivers. I worked with O2 drivers, reading the A2D inputs and PWMing the sensors to heat them up quicker to achieve closed loop fueling quicker. I did the drivers for the fuel subsystem, which included fuel pump and its diagnostic feedback and the fuel injectors. So I had a lot of day to day contact from the open loop control system feature engineer and the closed loop engineer. My fuel high level driver was supposed to be simple, take a fuel mass and convert it into an injector time on, then write the value to a device called a TPU, Time Processor Unit, and that would in turn, control the injectors. Well, it wasn't that simple and my fuel high level driver turned out to be a mammoth of a driver. I learned a lot from it. I even submitted an ROI, record of invention, for an algorithm that would eliminate the daunting task of selecting the first cylinder to receive a sequential pulse when transition from simultaneous fueling via calibration. My algorithm removed the calibration. It was really called trickle fueling and the algorithm was used at really cold temperatures and the first vehicle it went into production on was the CD338 I4 and v6, AKA 2006 Ford Fusion. BTW, I didn't get a patent that I applied for because I left the company. Bummer.

 

[turbodave231]

Charles,

I didn't know your level of understanding! On this board we try to help everyone. I am fairly sure that the ECM's used in our cars are not nearly on the level of the software you have developed.

I beleive the reason for the Closed loop requirement is to ensure the engine is at full operating temps. Bob Bailey might be able to give us a better answer.

 

[Eric Stage I]

Dave is correct. No need for closed loop. Just make sure it's warmed up (160 or above).

Also, the 500-550rpm in the procedure was based on factory idle speed, which was pretty low. You might want to use a number that is 100-150rpm under the commanded idle speed of the chip, or just shoot for IAC around 10-20.

Regards,
Eric

 

[jlat]

hello people; And hello to the TT guy. What happens if you can't get the numbers you say to shoot for?. I forget the numbers I have but it's not in the 10-20 range.
IBBY

 

[MCH86GN]

hello people; And hello to the TT guy. What happens if you can't get the numbers you say to shoot for?. I forget the numbers I have but it's not in the 10-20 range.
IBBY

Find out what your numbers are at warm idle. My problem is I started off with a vacuum leak and that seemed to really mess my idle up. I hope it is just an idle air/speed control problem.

I also attached a pdf file Idle Speed Control that I downloaded from Eric's website. It does have some basic information in it that might be of value. However, it does go in depth into the ECM code and start talking about register addresses, look-up tables and also what type of method that is used to control the engine idle speed. Unless you have ever implemented a PID controller or had a class in control theory, it might tough to pick up on the engine idle speed control method. Although it isn't worded too technically and the author doesn't use a bunch of equations, but it is definitely beyond the scope your asking.

 

[278cikiller]

Charles,

Loop status should not matter to get the minimum air rate correct. You do need to get the engine full warmed up. To set minimum air rate:

1. Warm the engine to full operating temps
2. Turn engine off and then turn the key back to ON
3. With the IAC connected, jumper pins A and B at the ALDL.
4. Wait 30 seconds and unplug the IAC
5. Remove the jumper at the ALDL
6. Start the engine
7. Adjust engine RPM to 500-550 in Drive using the throttle stop screw on the throttle body.
8. Shut the engine off and plug the IAC back in.
9. Restart the engine
10. Set TPS to .40-.44 volt or whatever your chip manufacturer specifies

At full operating temps, the IAC counts on a scanmaster or scan tool should be somewhere in the 20-40 count range at idle. The IAC counts go up as you open the throttle (throttle follower function)


If you have a vacuum leak, you may not be able to obtain a low enough idle speed during the above procedure. Air is entering the intake manifold and not going through the throttle body.

What happens when you don't have the ALDL port under the dash to jump the A & B pins ? The reason i ask i have a 1982 regal with the Stage II motor in it.

 

[turbodave231]

I use a tool made by OTC. This test tool allows me to take complete control over the IAC motor. Unplug the IAC motor and plug in the tool. A toggle switch allows me to directly control idle speed. The tool tests the range of the IAC and drives the pintle it to its seat. I like this tool because I can verify that the IAC works smoothly and is also great for setting minimum air rate after cleaning the TB.

 

[278cikiller]

I use a tool made by OTC. This test tool allows me to take complete control over the IAC motor. Unplug the IAC motor and plug in the tool. A toggle switch allows me to directly control idle speed. The tool tests the range of the IAC and drives the pintle it to its seat. I like this tool because I can verify that the IAC works smoothly and is also great for setting minimum air rate after cleaning the TB.

View attachment 179327

That,s a lot to bi just to set the IAC. Thank's Is there another way to a just it?

 

[mgmshar]

MCH86GN: As someone who worked in the OBDII calibration group at one of the OEM's (back in the late-90's), one of the first things I had to learn is that the code and processing power in these cars is orders of magnitude simpler than the stuff we worked on. If you really want to see how simple, look-up the code dump from the stock ECU and PROM chip at the web site below. Remember, when these ECU's were in production, the Commodore-64 was the hot home computer (still have mine, still works, still play games on it once in a while, but I dirgress...). Look in the "ECM secrets revealed" and "Chip secrets revealed" to get an idea.

http://www.gnttype.org/techarea/ecmsensors/ecmpage.html

OTHERS: The bottom line is that your car needs to be fully warmed-up when you set the TPS and IAC. If you chip runs open-loop idle, it doesn't matter - just set TPS and IAC when the car is fully warmed-up on a average day. I put a procedure that I've used for years in the thread below (see Post 44). This procedure requires some sort of scan tool that can read TPS volts and IAC counts (Scanmaster, OTC-2000, PowerLogger, etc.). You do not need to ground the ALDL connector for this procedure.

http://turbobuick.com/forums/thread...ease-help-video-with-scanmaster.384772/page-3

The earlier-referenced procedure by TurboDave (Post #2) is a good way to get an initial IAC and TPS setting if you don't have a scantool of any kind (you can use a voltmeter to measure the TPS voltage at the end of the procedure). However, if you have a scantool, I believe it's better to follow the procedure that I wrote in the link above (which is essentially the same as the "with scantool" procedure on gnttype.org).

One other thing - keep in mind that your IAC counts at idle will vary quite a bit even if everything is perfect (no vacuum leaks, etc.). For example, if you set the IAC to be at 20 counts at idle on a hot day, they will be much lower (maybe even zero) when your car is idling on a cold day, because the air coming into the engine is denser. Therefore, less air volume is needed to keep the car idling, and IAC counts go down. Also, if your fans are running, A/C is turned on, headlights are on, etc. all of those will affect the load on the engine and affect how many IAC counts are needed to maintain idle speed. When my "ramchargers" fans kick-on, my IAC counts go up about 4 or 5 counts just due to the higher electrical load on the alternator. Bottom line - adjust your IAC and TPS to decent values when the car is fully warmed and idling "normally", and then don't be surprised when the IAC counts are different on different days.

HTH

 

[turbodave231]

Well said Mike!

 

[278cikiller]

MCH86GN: As someone who worked in the OBDII calibration group at one of the OEM's (back in the late-90's), one of the first things I had to learn is that the code and processing power in these cars is orders of magnitude simpler than the stuff we worked on. If you really want to see how simple, look-up the code dump from the stock ECU and PROM chip at the web site below. Remember, when these ECU's were in production, the Commodore-64 was the hot home computer (still have mine, still works, still play games on it once in a while, but I dirgress...). Look in the "ECM secrets revealed" and "Chip secrets revealed" to get an idea.

http://www.gnttype.org/techarea/ecmsensors/ecmpage.html

OTHERS: The bottom line is that your car needs to be fully warmed-up when you set the TPS and IAC. If you chip runs open-loop idle, it doesn't matter - just set TPS and IAC when the car is fully warmed-up on a average day. I put a procedure that I've used for years in the thread below (see Post 44). This procedure requires some sort of scan tool that can read TPS volts and IAC counts (Scanmaster, OTC-2000, PowerLogger, etc.). You do not need to ground the ALDL connector for this procedure.

http://turbobuick.com/forums/thread...ease-help-video-with-scanmaster.384772/page-3

The earlier-referenced procedure by TurboDave (Post #2) is a good way to get an initial IAC and TPS setting if you don't have a scantool of any kind (you can use a voltmeter to measure the TPS voltage at the end of the procedure). However, if you have a scantool, I believe it's better to follow the procedure that I wrote in the link above (which is essentially the same as the "with scantool" procedure on gnttype.org).

One other thing - keep in mind that your IAC counts at idle will vary quite a bit even if everything is perfect (no vacuum leaks, etc.). For example, if you set the IAC to be at 20 counts at idle on a hot day, they will be much lower (maybe even zero) when your car is idling on a cold day, because the air coming into the engine is denser. Therefore, less air volume is needed to keep the car idling, and IAC counts go down. Also, if your fans are running, A/C is turned on, headlights are on, etc. all of those will affect the load on the engine and affect how many IAC counts are needed to maintain idle speed. When my "ramchargers" fans kick-on, my IAC counts go up about 4 or 5 counts just due to the higher electrical load on the alternator. Bottom line - adjust your IAC and TPS to decent values when the car is fully warmed and idling "normally", and then don't be surprised when the IAC counts are different on different days.

HTH

Thank's for all your help guys.

 

[larry33kc]

How do you set it if you have an aftermarket ECM like Bigstuff 3?

 

[MCH86GN]

Mike,

Thanks for your input.

 

[MCH86GN]

Dave,

I hope you didn't take offense to my post, that wasn't my intent. You and Eric together answered my question. As long as the engine warm enough. Then Eric explanation about having a higher idle with the TT 6.0 chip than with the stock, is probably why I am not seeing my RPM after reset go to 500-550, it is more like 675-725.

I will try to reset and adjustment procedure when I get time. I did type up a reply to you and when I clicked post, it said I needed to log in again and I did without copying my post, so I lost my post and I didn't feel like retyping such a long post. Not sure if it is the browser or the site that is logging me out, but it has done it a couple of times.

Anyway, things have taken a different turn for me. When I was driving home Friday night, I stopped at a light in my 2000 S10 and my oil pressure went to 0! Likely a cam bearing wearing out. I did change the oil, it was time, and added some coolant and my oil pressure isn't going to o now at hot idle, but it is still lower than normal at hot idle than usual. So I might have to put my plans with my GN on hold, pending what I do with my truck. It has 160k miles on it and I'm not sure if I want to replace the engine or replace the vehicle.