Idle air vs IAC park position
05-15-2004, 05:04 PM
#41
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There's an Allen screw that is on the side of TB. You will spot it. Remove it and remove the small ball behind it. Be careful it is small. You need a voltmeter with a sharp point type end on the testing wire. With the key on find which wire from the TPS connector gives a reading. One full turn of the screw behind the ball is about .10V. When the allen screw is repaced use some blue caulk.
It seems that the blade seats based on the voltage. That's what we wanted to determine. You can see the change in the Blade position, with the key on only, as you make the changes.
Goodhands, the car's idle tune held up well until I drove it on the highway for a while. It then developed a 300rpm cruise. I had lowered IAC Reset and that worked to lower the startup rpm surge. No combo of values seemed to remove that one cruise effect. It just seemed that the PCM did well under stop and go conditions. It appeared to have been going back to some basic setting after prolonged driving at constant speed. It seemed the blade position could be the culprit. Looks like it was.
It seems that the blade seats based on the voltage. That's what we wanted to determine. You can see the change in the Blade position, with the key on only, as you make the changes.
Goodhands, the car's idle tune held up well until I drove it on the highway for a while. It then developed a 300rpm cruise. I had lowered IAC Reset and that worked to lower the startup rpm surge. No combo of values seemed to remove that one cruise effect. It just seemed that the PCM did well under stop and go conditions. It appeared to have been going back to some basic setting after prolonged driving at constant speed. It seemed the blade position could be the culprit. Looks like it was.
Last edited by gojo; 05-15-2004 at 05:15 PM.
05-15-2004, 10:14 PM
#42
Originally Posted by gojo
There's an Allen screw that is on the side of TB. You will spot it. Remove it and remove the small ball behind it. Be careful it is small. You need a voltmeter with a sharp point type end on the testing wire. With the key on find which wire from the TPS connector gives a reading. One full turn of the screw behind the ball is about .10V. When the allen screw is repaced use some blue caulk.
It seems that the blade seats based on the voltage. That's what we wanted to determine. You can see the change in the Blade position, with the key on only, as you make the changes.
Goodhands, the car's idle tune held up well until I drove it on the highway for a while. It then developed a 300rpm cruise. I had lowered IAC Reset and that worked to lower the startup rpm surge. No combo of values seemed to remove that one cruise effect. It just seemed that the PCM did well under stop and go conditions. It appeared to have been going back to some basic setting after prolonged driving at constant speed. It seemed the blade position could be the culprit. Looks like it was.
It seems that the blade seats based on the voltage. That's what we wanted to determine. You can see the change in the Blade position, with the key on only, as you make the changes.
Goodhands, the car's idle tune held up well until I drove it on the highway for a while. It then developed a 300rpm cruise. I had lowered IAC Reset and that worked to lower the startup rpm surge. No combo of values seemed to remove that one cruise effect. It just seemed that the PCM did well under stop and go conditions. It appeared to have been going back to some basic setting after prolonged driving at constant speed. It seemed the blade position could be the culprit. Looks like it was.
Great info. What is "blue caulk" - my stupidity always amuses me
?I sent you an email/files.
The screw adjusts the base voltage to the Tb Blade - right? The voltage holds the blade open a given amount - for a given voltage. This is the baseline opening of the Tb Blade?? At zero volts is the blade closed?? Is this basically the same as a throttle stop set screw on a cable setup -fbod.
I think I told you I Edited my PCM just before leaving on a 200 mile trip. After about 1 1/2 hrs. I pulled off the interstate for gas and it "cruise controlled". I thought it was because I neglected to do a relearn.....I think I need some blue caulk.
Thanks !!!
joel
05-15-2004, 11:01 PM
#43
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I should have said Blue Loctite. It happens a lot these days.
The Voltage reading on mine, with the key on, is now .48. I believe it's a little higher on a stock TB. I would guess that 0 would close the TB completely. This sets the position slightly open. It seems to be very sensitive to where it's set. Not a surprise. Before trying these settings, I would have guessed that the IAC reset did this. Reset does set the blade position at startup, but it looks like the Voltage sets the blade position for cruising as well. It seems to be a permanant resting place, whereas the reset is for start only. If these findings are right, cruise would always come back in those cases where voltage is too high. Obviously I have not figured it all out. Raf's make sense, but what do the IAC's do? Is it a matter of getting the Voltage and IAC's in sync?
I got the files. thanks. I'm planning to look at them tomorrow.
The Voltage reading on mine, with the key on, is now .48. I believe it's a little higher on a stock TB. I would guess that 0 would close the TB completely. This sets the position slightly open. It seems to be very sensitive to where it's set. Not a surprise. Before trying these settings, I would have guessed that the IAC reset did this. Reset does set the blade position at startup, but it looks like the Voltage sets the blade position for cruising as well. It seems to be a permanant resting place, whereas the reset is for start only. If these findings are right, cruise would always come back in those cases where voltage is too high. Obviously I have not figured it all out. Raf's make sense, but what do the IAC's do? Is it a matter of getting the Voltage and IAC's in sync?
I got the files. thanks. I'm planning to look at them tomorrow.
05-15-2004, 11:45 PM
#44
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A couple of questions gojo. (my ignorance knows no bounds)
Where the hell is this "screw on the side of the TB" is it on B1 or B2 side. Do have to take something off first to see it? I must be freakin blind all I see are the screws holding the black sensor on B2 side of the Tb and the ETC motor or whatever that is on B1 side. What was your voltage before making any adjustments? I am experiencing some rpm drop off when rolling up to a stop. It seems like the blade is closing to much then the PCM compensates/corrects. Do you think adjusting the tps voltage upward may help this? Thanks for the info.
Where the hell is this "screw on the side of the TB" is it on B1 or B2 side. Do have to take something off first to see it? I must be freakin blind all I see are the screws holding the black sensor on B2 side of the Tb and the ETC motor or whatever that is on B1 side. What was your voltage before making any adjustments? I am experiencing some rpm drop off when rolling up to a stop. It seems like the blade is closing to much then the PCM compensates/corrects. Do you think adjusting the tps voltage upward may help this? Thanks for the info.
05-16-2004, 12:13 AM
#45
goodhands - looks like about a 3-4 mm set screw. On the front of the B1 side??? If memory serves me right ( we're on thin Ice!)
gojo - my previous understanding was that "Reset IAC Park Position" was the default position of the blade after power interuption to the PCM - battery disconnect or reflash. "IAC Park Position" - was the Position of the blade at Start up/Cranking. So after a reflash mine would start at 310 steps then swing to 124 steps.
I noticed that the blade NEVER dropped below 0.4% TPS - during surging etc. it never fell below 0.4%. Do you think the blade voltage you've measured coincides with this 0.4%?? It would make sense that it does. But then how does the PCM zero it out at start up?? (GM manual says TPS voltage output is basically zeroed at start up - that's why it's not important that our TPS output voltage read 0.00 volts at 0% TPS. If it was at 0.49 volts, at closed throttle, this would be the 0% TPS- GM pid? The SAE and GM TPS% Pids are different.) ....or is it the TAC system that zeroes it?? I guess it would make sense that the TAC system would interpret and integrate the voltage - Not the PCM?? TAC is a 0-5 Volt referenced system, triple redundant, I think?
I have Blue Loctite now all I need is my car!!
gojo - my previous understanding was that "Reset IAC Park Position" was the default position of the blade after power interuption to the PCM - battery disconnect or reflash. "IAC Park Position" - was the Position of the blade at Start up/Cranking. So after a reflash mine would start at 310 steps then swing to 124 steps.
I noticed that the blade NEVER dropped below 0.4% TPS - during surging etc. it never fell below 0.4%. Do you think the blade voltage you've measured coincides with this 0.4%?? It would make sense that it does. But then how does the PCM zero it out at start up?? (GM manual says TPS voltage output is basically zeroed at start up - that's why it's not important that our TPS output voltage read 0.00 volts at 0% TPS. If it was at 0.49 volts, at closed throttle, this would be the 0% TPS- GM pid? The SAE and GM TPS% Pids are different.) ....or is it the TAC system that zeroes it?? I guess it would make sense that the TAC system would interpret and integrate the voltage - Not the PCM?? TAC is a 0-5 Volt referenced system, triple redundant, I think?
I have Blue Loctite now all I need is my car!!
05-16-2004, 07:50 AM
#46
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Goodhands,
On the drivers side, run your fingers under the front of the TB. To set it requires removing the TB. I think stock is about 5v. I don't think it should be used for tuning. But I would check the voltage to be sure it's set right. The blade will open at full throttle with the key on to almost full. Maybe 1/8 shy of full.
Joel,
I tested the IAC reset by going down to 250, which brought the start rpm's way down and caused the car to stall on startup. 300 dropped my start rpm's from 1400 to 1200. Do you think the reset position affects how high the idle goes right at start and IAC's is where the blade settles. It required doing the hard reset for the changes to take effect. None of my start files show TPS being 0'd at start. It again sounds like all must be in sync.
I would be interested in getting some info from someone that can explain the system.
On the drivers side, run your fingers under the front of the TB. To set it requires removing the TB. I think stock is about 5v. I don't think it should be used for tuning. But I would check the voltage to be sure it's set right. The blade will open at full throttle with the key on to almost full. Maybe 1/8 shy of full.
Joel,
I tested the IAC reset by going down to 250, which brought the start rpm's way down and caused the car to stall on startup. 300 dropped my start rpm's from 1400 to 1200. Do you think the reset position affects how high the idle goes right at start and IAC's is where the blade settles. It required doing the hard reset for the changes to take effect. None of my start files show TPS being 0'd at start. It again sounds like all must be in sync.
I would be interested in getting some info from someone that can explain the system.
05-16-2004, 08:41 AM
#47
gojo - have you scanned with these two pids, side by side, and noted their values??
Added {GM.ETCIDLE_A} Desired Throttle with Idle Contribution"
Added {GM.ETCIDLE_B} Desired Throttle without Idle Contribution"
I wanted to - never got to it.
I thought, after a flash, the IAC reset would set the blade at one position (stock = 310). Then as car started/cranked the blade would need to move to the IAC Park Position. IAC Reset at 160 ( vs 310) would reduce the travel to IAC Park. Sort of a coarse refinement. I guess that's wrong??
joel
Added {GM.ETCIDLE_A} Desired Throttle with Idle Contribution"
Added {GM.ETCIDLE_B} Desired Throttle without Idle Contribution"
I wanted to - never got to it.
I thought, after a flash, the IAC reset would set the blade at one position (stock = 310). Then as car started/cranked the blade would need to move to the IAC Park Position. IAC Reset at 160 ( vs 310) would reduce the travel to IAC Park. Sort of a coarse refinement. I guess that's wrong??
joel
Last edited by Bink; 05-16-2004 at 09:09 AM.
05-16-2004, 09:06 AM
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[QUOTE=Bink]gojo - have you scanned with these two pids, side by side, and noted their values??
Added {GM.ETCIDLE_A} Desired Throttle with Idle Contribution"
Added {GM.ETCIDLE_B} Desired Throttle without Idle Contribution"
I don't think they are available.
Joe
Added {GM.ETCIDLE_A} Desired Throttle with Idle Contribution"
Added {GM.ETCIDLE_B} Desired Throttle without Idle Contribution"
I don't think they are available.
Joe
05-16-2004, 09:10 AM
#49
I edited above - me slow.
gojo - the "learned' calculated Airflow values are held in the PCM memory. You might have to disconnect or pull fuse to erase them. I had to pull fuses for each run/scan when evaluating the VE equations. The Airmass values were stored and the only way to start fresh for each run was to pull fuses for a couple minutes. FWIW.
gojo - the "learned' calculated Airflow values are held in the PCM memory. You might have to disconnect or pull fuse to erase them. I had to pull fuses for each run/scan when evaluating the VE equations. The Airmass values were stored and the only way to start fresh for each run was to pull fuses for a couple minutes. FWIW.
Last edited by Bink; 05-16-2004 at 09:23 AM.
05-16-2004, 09:34 AM
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I see it (set screw) now! I'll go to Sears this morning and get a voltmeter that reads <1 volt, mine reads 1>. Maybe they will have some of that blue caulk too????. I think I will give this a shot for my rpm drop off problem. I have the RAF's pretty high now and it has not seemed to make a difference in the RPM drop off. I was thinking this is a blade postion thing too (blade closing to much). Hopefully I will get some time today to give this a try. 
05-16-2004, 09:35 AM
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"I thought, after a flash, the IAC reset would set the blade at one position (stock = 310). Then as car started/cranked the blade would need to move to the IAC Park Position. IAC Reset at 160 ( vs 310) would reduce the travel to IAC Park. Sort of a coarse refinement. I guess that's wrong?"
I don't know if you're wrong. You could be describing the same as what I found. ie: that lowering IAC Reset, caused the jump in RPM's to be lower.
I don't know if you're wrong. You could be describing the same as what I found. ie: that lowering IAC Reset, caused the jump in RPM's to be lower.
