Can I manually manipulate my idle speed? (Page 7/10)
Kitskaboodle APR 24, 07:16 PM
Yes, the IAC gasket is there.
Oh, in case you think I forgot, I did Gumout quite thoroughly the IAC hole in the side of the throttle body after I took out the old one.
And as I said, I have 3 spare MAP sensors. I tried the GM one first but if it helps I can try the other 2, although they are off brand.
My throttle body butterfly looks like it’s in great shape with no corrosion like you mentioned. That and it is very clean with almost no carbon buildup.
Patrick, I’m still on the fence about messing with the idle screw….
Looking into a scan tool now……. Kit

[This message has been edited by Kitskaboodle (edited 04-24-2025).]

Romsk APR 24, 09:09 PM
Kit,

Too bad we aren't all just hanging over your engine with beers in hand, I bet it would be resolved by now [smile]. I see a lot of good advice tossed around here. You may be looking at multiple problems, but hang in there.

On a side note: I will be borrowing a 1985 V6 ECM to revamp my GUI. I know that is no help now, but I will try my best for the future.

Me? Personally, I am not convinced that suddenly plugging the TB inlet and the engine instantly stalling is a definite diagnosis that rules out vacuum leaks. There may still be a slight leak somewhere. I feel that choking off an engine that severely and suddenly will make any engine stall instantly (even with a small vacuum leak) - there simply is not enough time for the ECM to recover from such a sudden rise in manifold absolute pressure (loss of inflow of air). But, I could be wrong... I think I was wrong once.... once [laugh].

Forgive me if already asked, did the idle problem just appear one day, or did it creep up over time?
Romsk APR 24, 09:54 PM
All,

For any of you that use my GUI, I added a Toggle ALDL Mode feature (it will be released tomorrow). You select that feature and it continuously toggles between NORM and DMDIAG Mode every couple of seconds. With Key On Egine Off (KOEO), this will allow you to test the IAC Valve by removing it and watch it go out (closed) in DMDIAG Mode and back in (open) in NORM Mode. I have a feeling that is why GM made the IAC Valve go to the closed position in DMDIAG Mode - to check the IAC Valve because there is no direct feedback of its position to the ECM.

My brother is a Subrau and BMW mechanic. He thinks that DMDIAG Mode in KOEO may also actuate the EGR Solenoid. If that is the case, we should hear the solenoid click on and off in ALDL toggle mode.
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Kit,

I agree with Patrick, the CTS and IAT Sensor should read about the same abmbient air temperature after letting the engine cool overnight. If you can unplug each and measure the over night rest pre-start resistance of each, I can plug those into my code and tell you their temperature readings and if they are working (at least at ambient). This might be something you can do as you look for a scan tool.

Biff
Patrick APR 24, 09:57 PM

quote
Originally posted by Romsk:

...the CTS and IAT Sensor should read about the same ambient air temperature after letting the engine cool overnight. If you can unplug each and measure the over night rest pre-start resistance of each, I can plug those into my code and tell you their temperature readings and if they are working (at least at ambient).



Of course, the problem with doing this is that it doesn't help determine whether or not that sensor info is actually making it to the ECU. There could be a wiring harness issue. But yeah, it's better than not doing any sort of reading at all.


quote
Originally posted by Romsk:

Me? Personally, I am not convinced that suddenly plugging the TB inlet and the engine instantly stalling is a definite diagnosis that rules out vacuum leaks. There may still be a slight leak somewhere. I feel that choking off an engine that severely and suddenly will make any engine stall instantly (even with a small vacuum leak) - there simply is not enough time for the ECM to recover from such a sudden rise in manifold absolute pressure (loss of inflow of air).



Well, how about if Kit goes about it very slowly then? Seriously though, if the mouth of the TB was covered over bit by bit, until it was completely blocked, and the engine stalls... would that not then convince you that there are no vacuum leaks (at least not enough of a leak to account for the high idle revs)?

If Kit was a little closer to Vancouver, I'd definitely be hanging over his engine bay by now.

[This message has been edited by Patrick (edited 04-24-2025).]

Romsk APR 24, 10:09 PM
Patrick,

I trust your judgment, but slowly covering the TB might provide some more data points.

I am an old school gear head... spraying carburetor cleaner was the only definitive way for a shadetree mechanic to determine if there are any vacuum leaks. That is too dangerous so I don't recommend it. Now they have fog (smoke) generators that are safer.

Yeah, I need to grab a beer on this one.
Patrick APR 24, 10:11 PM

quote
Originally posted by Romsk:

With Key On Egine Off (KOEO), this will allow you to test the IAC Valve by removing it and watch it go out (closed) in DMDIAG Mode and back in (open) in NORM Mode.



Is that really a good idea? On one of my Fieros, I powered up the IAC valve while it was removed from the TB, and the pintle shot off into the lawn!
Romsk APR 25, 03:30 PM
Patrick,

Mine had a stop. It did not shoot off when I made a dual H bridge module and Arduino UNO bench test for it. Then I pulled the pintle out a couple of times as I was honing the code. I pulled it a little too hard, broke the internal stop, and it popped out.

So, I guess some have stops, and some don't, or someone in the past at least mishandled and broke a stop.

In my GUI help, I have details on these facts and to do it on a cool engine and to put the IAC Valve in a box in case the stop is broken or not even present. I may make a little fixture for it so the pintle can't pop out when removed from the TB.

So that GUI version is now posted on my web page for my whopping 20 users world wide [laugh].

Now I am modifying the ALDL Adapter with a tiny slide switch to select pin M 8192 Baud or pin E 160 Baud. I ran of I/O on the tiny $9 Trinket Microcontroller Board, so I have to switch the signal manually. The GUI sends mode commands to the Adapter, I have to add a command to detect 8192 Baud or 160 Baud timing. Then update the GUI code to handle the 5 different ECMs (and ALDL streams) that stock Fieros use.

My Adapter does not work like those simple adapters that try to treat the ALDL as an RS-232 data frame. Mine actually measures the pulses down to the micro second and determines if the ALDL data represents a logic 1 or 0 bit. Then the Adapter sends an ASCII '1' or '0' respectively over USB at a 500K Baud rate to the GUI. So, it will be able to convert 8192 Baud bit streams just as effectively - plenty of time between ALDL pulses.
fierosound APR 27, 09:23 AM

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Kitskaboodle APR 30, 12:34 AM
Thanks Fierosound for the FSM screenshot.
Good news is I just got my FieroStore Scantool in the mail today. Next step is to contact my friend who is giving me a free laptop. (mine is too old and missing the power brick besides) After we load the software we will get it up and running and report back with the real time parameters.

Patrick, I was thinking that same that I wish you were all physically here to assist me. Doing it by myself is kind of depressing and i feel all alone working on it by myself. Anyone have a tissue?😩
Kit

[This message has been edited by Kitskaboodle (edited 04-30-2025).]

Patrick APR 30, 12:52 AM

quote
Originally posted by Kitskaboodle:

Good news is I just got my FieroStore Scantool in the mail today. Next step is to contact my friend who is giving me a free laptop. (mine is too old and missing the power brick besides) After we load the software we will get it up and running and report back with the real time parameters.



I'm not familiar with that scan tool, I don't know what software is packaged with it and/or how the info is displayed.

With WinALDL, I found that Cliff Pennock's utility program, ALDLView, was a great help in seeing/understanding the data.


quote
Originally posted by Kitskaboodle:

I wish you were all physically here to assist me. Doing it by myself is kind of depressing and i feel all alone working on it by myself. Anyone have a tissue?😩



I usually work on my cars alone, with maybe just the cat for company. If only she had opposing thumbs, she could at least pass me the tools.