IAC tuning. Am I crazy? (Solved!)

Philip Lochner · Post by **Philip Lochner** » Mon May 01, 2006 11:16 am

grippo wrote:One other thing that may be causing confusion is the time based after start. What this means is...

Dear Mr Grippo

I know I'm blonde but now you have REALLY confused me...for one...

The way you present "time based after start" here seems (!! to me !!) quite the opposite of the way the feature is presented in the "Tuning your MS-2" manual - which seemed most sensible to me (except that I can't seem to get "time based after start" to work) but now... sigh

Are you saying that "Time Based after start" only becomes active AFTER the "cold temp" value, ie, at HIGHER TEMP values than the "cold temp" value? If this is the case then surely to totally "disable" this feature one should enter a "cold temp" value of MORE than the HIGHest temp the engine will ever reach ie not "0" but say, "250F".

Based on the manual, I interpreted this "Time based after start" feature as follows:

It is useful for when the engine is REALLY cold, allowing one to crank the engine with a VERY open IAC say (50 of 200 = > Cranking pos), then because the engine is COLDER than "Cold temperature", IAC would go from the "Cranking position" to the "cold position" (say 80 of 200), allowing one to have the engine "idle" rather high immediately after the engine fires, say 1300rpm, but THEN reduce the RPMs rather quickly over the "cold taper time" period (say 5 sec), to the IAC position specified by the temp table - a period over which CLT temp variations would be too small to allow for sensible temp table based IAC control. In my mind it would then make sense to have the temp table START at this value of 80 and ending at 200.

If CLT is above "Cold Temp", IAC would jump from cranking position straight to the temp table (This is what mine does ... when it does not "jam" in the open position)

Post by **grippo** » Mon May 01, 2006 12:03 pm

There are 2 separate features. The time based works like this:

1. it only applies when the startup coolant is < user input
2. The ECU provides steps from the coolant vs step table up until a user input step position that should be below the close position, that is more open than the close position. When it gets to this point, the steps no longer come from the table - they are calculated from a straight line from the position at start of time-based to the close position, over the amount of time you want to take(another user input). This will very rarely be used because most people only need enrichment until warmup temperature is reached. But on very cold days, some people may require longer than this before they can close the stepper. To get rid of it, you can specify a very cold startup temp. (You could also fool it by a step position > close, or by a tape time of 0.

The second feature, which is much more useful, is to leave the stepper position open to at least as much as <user input> during cranking, regardless of how hot the coolant may be. Once cranking is done this will taper into the regular table driven step postion over a period of <user input>. To get rid of it set a cranking position > max steps, that is fully closed. (Fully open is 0 steps.)

bluetrepidation · Post by **bluetrepidation** » Mon May 01, 2006 4:18 pm

OK got the new processor in today. Jumped large resistors. Flashed with 3.35 code. Set to 15 min IAC. I had a little time and I did notice the "noise" I was feeling on the motor was gone. Because the resistors where jumped I assume. When I get more time I'll be sure to observe the motor movements from a cold start and get back to you.

A.J.

Post by **grippo** » Mon May 01, 2006 7:27 pm

I tested some more tonight and am able to consistently move my motor through a very slow warmup (on the stim) all the way to fully closed even with the Moving Only option. However, I did create a new test code version which only moves the stepper after at least 4 requested steps have accumulated. This appears to work equally well for me so I am attaching a download file if anyone wants to test it. It is version 2.35 with only the 4-step min modification.added. If this works we can refine it a bit and make the 4 step min a user input. This may end up with 3 less than the max number of steps when fully closed, but this value should always be chosen about 10 or 20 steps more than required for full closure, so it won't matter.

If anyone needs a 2.67 version, I can make that available also.

krisr · Post by **krisr** » Mon May 01, 2006 7:40 pm

I'm using 2.54 at the moment (want to test AMC), would it be possible to get it added into that and i'll give it try one night this week?

Cheers

Post by **grippo** » Tue May 02, 2006 7:03 am

v2.54 was kind of an intermediate version which I moved into v2.6 and started adding from there. The 2.6 series is totally back-compatible with the 2.5 series - and new features are turned off by default, so I believe you should be able to run with v2.6x. I already made a test version of this so I'd like you to try it. If you have compatibility problems (but ignore any warning in MT that you have the wrong version no.) I will make a 2.5 version and send it to you.

Post by **Bruce Bowling** » Tue May 02, 2006 7:53 am

One thing also I want to have everyone verify is the motor wiring. Take 30 seconds with an ohmmeter and verify that the 2 stepper coils come out of the IAC pins in the correct place. Out of the 4 pins there are two separate coils, verify the arrangement with the ohmmeter. I want to make sure it matches what we have on the list, just to eliminate this as a potential issue. Measure it directly and let us know the image in the documents matches what you measure - this is very important.

I know from having a mis-wired stepper that there are mis-wiring arrangements that will yield motor movement but wll also act flaky at the same time.

- Bruce

JSC · Post by **JSC** » Tue May 02, 2006 12:38 pm

A.J.

Here are the waveforms I promised. These were taken as I started the truck, the retract was after key on while the IAC was going to the home (0) position and the extend was going to low idle. The half step you were seeing must have been something on your board.

Bruce & Al

Myself and my MS buddy here have IAC's that have been working very well. As I've stated in posts above, we've changed the RC components for the stepper driver and have no jumpers on the resistors. We are running a 5.0 ms step size. I'll try 2.5 and report back. I'm at somewhat of a loss as to what I can do to help now that mine is working. If you think of something, let me know.

My setup; MSII, V3, 2.35, GM O-ring IAC.

Buddy setup; MSII, V2.2, 2.32, GM square IAC.

Scott

BottleFed70 · Post by **BottleFed70** » Tue May 02, 2006 7:35 pm

grippo wrote:I tested some more tonight and am able to consistently move my motor through a very slow warmup (on the stim) all the way to fully closed even with the Moving Only option. However, I did create a new test code version which only moves the stepper after at least 4 requested steps have accumulated. This appears to work equally well for me so I am attaching a download file if anyone wants to test it. It is version 2.35 with only the 4-step min modification.added. If this works we can refine it a bit and make the 4 step min a user input. This may end up with 3 less than the max number of steps when fully closed, but this value should always be chosen about 10 or 20 steps more than required for full closure, so it won't matter.

If anyone needs a 2.67 version, I can make that available also.

Hi Al,

I gave the 2.35x1 code a try today with mixed results.

For some reason this code didn't work? The IAC was not moving in 4 step intervals. Luckily I datalogged the warmup, and you can clearly see in the datalog that it was moving in random steps from 1 to 4. 1,2,and 3 step movements were the most common, but it did take a few steps of 4. Please see the attached datalog.

The good news was that when it did move in 3 or 4 step intevals I believe I was actaually able to hear the engine RPM drop slightly, although it was hard to tell. Also, in the end my idle was lower that it normally was..so I believed the IAC moved further this time, but still not enough.

I've also attached a 2nd datalog of a warm start in order to demonstrate the difference. This 2nd datalog was taken only seconds after the 1st.

BottleFed70 · Post by **BottleFed70** » Tue May 02, 2006 7:46 pm

Bruce Bowling wrote:One thing also I want to have everyone verify is the motor wiring. Take 30 seconds with an ohmmeter and verify that the 2 stepper coils come out of the IAC pins in the correct place. Out of the 4 pins there are two separate coils, verify the arrangement with the ohmmeter. I want to make sure it matches what we have on the list, just to eliminate this as a potential issue. Measure it directly and let us know the image in the documents matches what you measure - this is very important.

I know from having a mis-wired stepper that there are mis-wiring arrangements that will yield motor movement but wll also act flaky at the same time.

- Bruce

Hi Bruce,

I checked my wiring today and I seem to have the "o-ring style" GM IAC with the inline 4 pin connector. I measured coil resistance of approx 47ohm/ Please see the attached picture as to how I have it wired into my relay board. I believe I jumpered everything properly during the build, but I must admit I found some of the IAC wiring instructions a little confusing.

One thing I couldn't tell from the picture was wether I'm supposed to be looking at this from the perspective of looking at the IAC pigtail connector or the IAC itself. Perhaps I have the polarity of both coils backwards? I took it from the perspective of looking at the IAC.

I'd love to do a continuity test from the IAC pigtail connector to the MSII daughter card(or elsewhere on the ecu) if you can give me some instructions on what I'm looking for? (IE which IAC pin should go to which MSII pin).