IAC tuning. Am I crazy? (Solved!)

pb3 · Post by **pb3** » Fri May 12, 2006 3:30 am

Good question about the resisters. I did mine, but I think from the calculations done, see a good few posts back, it is probably not that necessary. The thinking was that the chip was current limiting and that is why steps were lost. As we now know that was not the issue and it was down to software.

If you do jumper them they are located on the MSII card, the small daughter board plugged into you V3 main board, they are the two big rectangles on the underside.

I have enjoyed the two and throwing on this thread, is it hardware, is it software, been there no end of times as a software engineer myself.

Many thanks to all those involved, it was driving my a little crazy as well.

Post by **grippo** » Fri May 12, 2006 5:32 am

As far as jumpering the resistors, I would try it without, but if it didn't work I would immediately jumper them. I found that, even with the 2.36 code fix, I still needed to jumper them to get mine to close all the way.

Post by **grippo** » Fri May 12, 2006 5:49 am

Ballistic wrote:Hmmm, I've now got a warmup idle that is 100-150 RPM lower than the idle speed on a restart. I increased step size from 2.5ms to 4.0 but it didn't seem to make a difference.

Do you have your steps set up so that when the coolant is at operating temperature the stepper pintle is fully closed, and you control your hot idle by cracking the throttle with a screw ? If that is your setup, then if it is a step inconsistency then your results imply that on a wam restart, the pintle doesn't fully close, but it does on a cold start. This is contrary to everyone's experience. The first thing is to do a data log and see if there is any difference in commanded steps between cold start and warm restart when you are at operating temp. If not and yet there is a difference in idle speed, then compare the enrichments, pulsewidth and timing advance. If there are differences, we can look at the log and your msq and see if we can find the reason for the differences. If there aren't, then try to see if there is truly a difference in the pintle opening. When you turn off the ignition, the pintle should remain in place, so examine its position to see if its truly closed. Then do a warm restart and re-examine.

TurboGt · Post by **TurboGt** » Fri May 12, 2006 8:47 am

Well my IAC is working much better, but I think I still need to jump my resistors because I still need a high start value to get the IAC to open all the way.

Could someone list which ones to jump for all the boards? Mine is a V3 board.

Thanks again to everyone who got this working.

Marq

bluetrepidation · Post by **bluetrepidation** » Fri May 12, 2006 10:53 am

The resistors are not on the board. They are on the bottom of your MS II daughter card. The two big black resistors. Jumper those and you should be good.

A.J.

TurboGt wrote:Well my IAC is working much better, but I think I still need to jump my resistors because I still need a high start value to get the IAC to open all the way.

Could someone list which ones to jump for all the boards? Mine is a V3 board.

Thanks again to everyone who got this working.

Marq

krisr · Post by **krisr** » Sat May 13, 2006 1:02 am

My IAC is still working perfect, no issues there, but has anyone else having RPM issues now with the new code by any chance? My car just then on a 150km round trip always kept dropping the rpm signal on me anywhere in the RPM range, recycle the ECU and it would start straight away again. It did this about 30 times in the trip.

I'm having a sneaking suspicion that another component in my VR circuit has gone dud again so i'll be building the LM1815 setup for a test.

Just thought i'd throw the question out there.

Kris

Ballistic · Post by **Ballistic** » Tue May 16, 2006 6:11 pm

Al, here's a warmup datalog and a copy of my .msq.

At the end of the datalog the idle was at 550, I turned off the engine and restarted, and the idle went to 850 with the same number of steps reported.

krisr · Post by **krisr** » Tue May 16, 2006 6:24 pm

Ballistic wrote:Al, here's a warmup datalog and a copy of my .msq.

At the end of the datalog the idle was at 550, I turned off the engine and restarted, and the idle went to 850 with the same number of steps reported.

Mine does the EXACT same thing. On warm up it's like it's out of sync with the steps but the minute you recycle the power after it's out of WUE, it operates perfectly.

Philip Lochner · Post by **Philip Lochner** » Thu May 18, 2006 12:48 am

grippo wrote:Hopefully this will solve the problem for many of you.

Got the car back from the gearbox shop. Tried 2.36 this morning. Seemed to work well. Certainly did not have the IAC "stuck" on wide open on the first start and did not have to restart. Even the bat was not too well after standing for longish time at gbshop.

Post by **grippo** » Sun May 21, 2006 7:56 am

Ballistic wrote:Al, here's a warmup datalog and a copy of my .msq.

At the end of the datalog the idle was at 550, I turned off the engine and restarted, and the idle went to 850 with the same number of steps reported.

I looked at the data log, msq and don't see anything fishy. It does seem the idle should be the same if the steps are the same. The only thing I see is that the IACStart steps is 355 but in the table the steps only go up to 290 at the highest temperature. The way this is meant to operate is that the last entry in the table should be the same as the IACStart value and the pintle should be fully closed. By making the max value a little larger than it needs to be you make up for any missed steps and can guarantee the pintle is fully closed. Then the idle is set by cracking the throttle plate. If you set the last table entry to 355 instead of 290 will you get a repeatable idle from cold and hot restarts ?

Also, I assume you have jumpered the large 1 Ohm resistors on the bottom of the board ?

As far as why the steps do not prove repeatable - I'm not sure at this point. We have verfied that the new software puts out proper steps on a scope, and it is showing the correct commanded steps in the data log. The only other thing I can think that might be a problem is the step velocity (step time). This definitely has an effect on motors which I have seen many times in work. I believe you tried 2.5 to 4.0 ms steps. Did it make any difference ? If not, did you try 1.5 ms ?