IAC-A/C Airflow (IAC_AC_DMA)

[ssheets]

What exactly is it? My idle wants to run away and it seems to be triggered by turning on the AC? I've looked over the logs and I do see a relationship between the two, but I don't know what is cause and what is effect?
I've attached a log of this event. Watch the TP%, RPM and IAC-Airflow.

I also noticed that my TP% is reading 0.4% when it should be 0%. Not sure about that...

[mr.prick]

http://forum.efilive.com/showthread.php?t=4661

[ssheets]

How much air will an IAC step count of 310 let by the throttlebody?
Using bidirectional control the max count is 127, but my log shows
a count of 310. Here's the sequence of events...
After removing the intake manifold to inspect for vacuum leaks on
the rear ports I found all mechanical connections to be in perfect
order. Here's some pictures of that exercise if anyone is interested.
http://i238.photobucket.com/albums/ff281/500hpss/intake%20removal/DSC_2809.jpg
http://i238.photobucket.com/albums/ff281/500hpss/intake%20removal/DSC_2827.jpg
http://i238.photobucket.com/albums/ff281/500hpss/intake%20removal/DSC_2822.jpg

After reassembly I started the car and let it warm up. Once warm I turned on
the AC and gave it a little throttle, it shows up 29% TPS at frame 22 in the
attached log. Of course MAP drops with throttle opening, but then the IAC
step count goes from 129 to 199 and then up to 310. Accordingly RPM goes
from ~900 idle to 3,400 when I gave it a brief 29% throttle and then instead of
settling back down to idle it drops to ~2,200 for a few seconds (while the
IAC is at the 199 step count) and then up to ~2,700 with the IAC at the 310
step count. MAP seems to follow with part throttle effect of the IAC. Here's
a screenshot showing the drum chart trends. I've also attached the log file.


http://i238.photobucket.com/albums/ff281/500hpss/EFI%20Live/IACsteps.jpg

This is pretty much what the problem is. It will go into a high idle condition
when I turn on the AC. It will idle at 2,200RPM with the clutch engaged and
then up above 3,200RPM when the clucth is disengaged. I've plugged off all
of the vacuum ports on the front and triple checked the ports on the rear.
The attached log file shows the IAC steps (apparently) driving this isssue. Am
I on the right track??

[ssheets]

More of the same...

If you create a chart with IAC steps, RPM, TP and IAC AC it sure is interesting. I don't know what it means, but it sure is interesting.

Everytime I turn on the AC the IAC counts go way up as does the idle. The IAC AC goes up a little. Once it goes into thigh idle the IAC step usually goes to 199 with an idle just above 2,000RPM, egage the clutch and the IAC step will got to 310 and idle over 3,000RPM. Turn off the AC and the idle will hunt around a little and then drop to normal with an IAC step count of 108ish. If I leave the AC off it drives normal.

[ssheets]

So no opinions????

I've read all of the links Mr. Prick offered and they do seem to address the whole air issue. I only have EFILive scanner and can not perform any tuning yet.

Before I spend another $250 I would like a little comfort stating that it is likely a tuning issue that I can correct with time, learning and EFILive tuning. Currently my tuner says the tune is perfect and I have a vacuum leak or something else is wrong with my motor. I have spent weeks double checking everything and isolating systems. The motor behaves perfectly until I turn on the AC. If I rev the throttle it will disable the AC compressor and the idle will normalize. If I turn off the AC the idle will normalize. If I leave the AC on it will sit at high idle sometimes indefinetly.

I was told by a few (not from this board) that if I bought the EFILive scan tool I could identify the problem. Now that I have the scanner all my advisors dissapeared and while I think I'm on to something I don't know enough verify it.

The attached logs in the above thread show what I'm talking about if you setup your dashpage to look at IAC Steps, RPM, TP and IAC_AC_DMA. I'd just like to know if you guys think it is a tuning issue or a mechanical issue??? Just point me in the right direction and I'll enjoy the puzzle.:)

[dfe1]

Judging by the texture of the ports, I'd have to guess you've also installed a camshaft of questionable duration in the past. If that is the case, your run-away idle is probably the result of an incompatability between actual MAP and airflow values and the original calibration, which is expecting far different values. The question I have is, whether this is a tuning issue or not, why would you attempt to work with a modified engine and NOT have tuning capability?

[ssheets]

Judging by the texture of the ports, I'd have to guess you've also installed a camshaft of questionable duration in the past. If that is the case, your run-away idle is probably the result of an incompatability between actual MAP and airflow values and the original calibration, which is expecting far different values. The question I have is, whether this is a tuning issue or not, why would you attempt to work with a modified engine and NOT have tuning capability?




Thanks and yes I should give all car and engine specs. I get my boards mixed up and thought I had my sig populated with the pertinent data.
The Car:
2002 Camaro SS LE convertible #3048. 345hp base package with Bilstein suspension package. Don Goetz sub frame connectors, strut tower brace, adjustable torque arm and tunnel brace.

Futral Motor sports F14 cam. 232/234 degrees duration, .600”/.600” lift on 112 LSA with 4 degree advance ground in.

Heads are custom built by Chuck Hebestriet. 60cc combustion chambers with 2.02” intake valves and 1.575” exhaust valves. Compression ratio is ~11:1. Hardened Chromalloy pushrods 7.400” by .080” with beefy valve seats for improved thermal transfer.

160-degree thermostat.

Ring and pinion are 4.10:1. Transmission is a Tremac T56 six speed with 6th gear at 0.5:1 for a cruise RPM of 1,600 at 60mph. Backlash on ring gear is .010” Summit racing girdled cast aluminum cover and solid crush sleeve are utilized.

Measured piston valve clearance is .100”/.180" intake/exhaust.

Headers are FLP long tubes with ORPs or high flow cats running through the OE SLP muffler and CME tips.

PCM with custom tune by wait4me performance.

The Story:

This is my first LSx project and my initial efforts focused on the mechanical side of things… I was told an email tune for my Diablo Sport Predator would take care of the tuning and I didn’t worry myself about it. As the head and cam swap closed in I found that the Predator was not going to cut it. The consensus on LS1tech was that while a dynotune was preferred a mail order tune should work. I found a few threads about Wait4me Performance and it sounded like he could get the job done. I think he does a great job and gets the tunes real close the majority of the time, but in my case there seems to be something amiss. When I first started the motor after the head and cam swap I used the old PCM with the Predator tune and it ran all right. The idle was low and hot re-start poor, but drivability and power were pretty good. Next I swapped to the PCM with the wait4me tune and as soon as I drove off the idle ran away. I gave it about 20 minutes and 5 miles to settle in, but the high idle speeds soon made it unsafe to drive. I swapped back to the PCM with the Predator tune and used my Predator handheld to get it better. I talked to Jesse and he said I had a vacuum leak “that’s the only way the tune would not run perfect. The OS and tune will adjust and run perfect unless you have a vacuum leak.” I checked all fasteners, hoses, connectors, O-rings, gaskets and even rotated the tires (I’m joking, but point being I have been thorough) and thought that the throttle body to intake manifold was the culprit as the bolts didn’t seem to be torqued down. I tightened them with great enthusiasm (likely overtorqued them now) and put the wait4me PCM back in. It ran great for about a week and I excitedly took the car out to take my wife to a Christmas party. It was a very cold night and I turned on the defroster. As soon as the AC compressor kicked in the idle went up to 3,000RPM. Not realizing the AC connection I called Jesse the next day and described the high idle. Again he told me that I had a major vacuum leak somewhere. Citing the cold temps (17*F) I considered that perhaps a thermal contraction was to blame? Jesse also told me that since I didn’t properly seal the rocker bolts all bets are off (paraphrased) as massive amounts of oil saturated air is leaking past the threads and into the intake ports. I called a few builders and they said that a good application of blue Loctite should seal the threads fine. (Further research tells me that some builders do use a sealer and some just Loctite them.) In the pictures above you can see how the intake ports look after ~1,200 miles of runtime since the build. The intake manifold and ports have a minimal coat of oil residue likely from the PCV system. Exactly which order the next events happen I can not remember for sure, but in these weeks I swapped PCMs back and forth, plugged off vacuum ports cussed at the wife and kicked the dog. The idle issue would only happen with the wait4me tune and capping off vacuum ports had no effect. I tried to use my Predator to watch LTFTs and O2 readings, but I was for all purposes blind. I was told by Jesse and a few members on LS1Tech that EFILive scanning would allow me to see the problem and then I could have it tuned out. So…I bought EFILive V1 (great tool) and started learning about PIDs and Dashpages. The car was running fine now by the way and I spent a week just enjoying EFILive as I trended my drives in-between snow storms on the few dry road days January in the shadow of the Sierra mountains affords. In a celebratory tone I called Jesse to tell him how great the car ran and ask what PIDs I should record to aid in fine tuning? On this day not only did the roads dry the temps rose and soon the cockpit of the car was more than warm. I reached for the AC knob…as soon as the AC compressor kicked in the idle went up to 2,200RPM. Depressing the clutch raised the idle to over 3,000RPM. After looking over the logs I finally had my eyes open. I could clearly see the IAC steps …108 normal idle, 199 AC on, 310 AC moving and engaging the clutch. This is as repeatable as the Sunrise on a summer day.

Well that pretty much brings us to the beginning of this thread.

I want to be clear that I’m not bashing Jesse or his service. I think he sells a great product for great deals. He has many satisfied customers and I hope to be one. I really don’t know if I have a tuning issue or??? I can honestly say I do not believe I have a vacuum leak.

Sorry for the book, but to include the facts over the last two months takes a bit of keyboarding. Thanks for any help you may give me in advance.

Tim

[ScarabEpic22]

Thanks for the specs man, others on here who know a lot more about this than I do appreciate the info.

I wonder if you can adjust the IAC steps manually on the tb so you dont have to delve into the electronic side, but Im not an expert on these engines (am on the 4.2L I6 LL8, lol) and cant tell you for sure.

Can you read the PCM with V1 Scan only? If so, please read your wait4me tune and just upload the idle portion under Engine Calibration->Idle (so you dont give his tune away on the net) by copying it into a stock Camaro tune (02 Stock Camaro Tune (http://www.holdencrazy.com/EFILive/TuneFileRepository/Stock/Chevrolet/2002%20Chevrolet%20Camaro%20Coupe%20Manual%20LS1%2 05.7%20Litre%20(PCM%2012212156).tun) from the repository). Im thinking there might be something in there thats affecting this, there is an A/C subcategory under Idle that may lead to the root of the problem.

[ssheets]

Thanks for the specs man, others on here who know a lot more about this than I do appreciate the info.

I wonder if you can adjust the IAC steps manually on the tb so you dont have to delve into the electronic side, but Im not an expert on these engines (am on the 4.2L I6 LL8, lol) and cant tell you for sure.

Can you read the PCM with V1 Scan only? If so, please read your wait4me tune and just upload the idle portion under Engine Calibration->Idle (so you dont give his tune away on the net) by copying it into a stock Camaro tune (02 Stock Camaro Tune (http://www.holdencrazy.com/EFILive/TuneFileRepository/Stock/Chevrolet/2002%20Chevrolet%20Camaro%20Coupe%20Manual%20LS1%2 05.7%20Litre%20(PCM%2012212156).tun) from the repository). Im thinking there might be something in there thats affecting this, there is an A/C subcategory under Idle that may lead to the root of the problem.
As far as I know I can not read the actual tune with the scan version only.
I can play with the IAC in bidirectional controls, but the max allowable command is 127. I don't know if that is the same thing as 127 step command or not? My scan shows steps as high as 310. A bidirectional command of 127 only raises the idle to about 1,800RPM as I recall...maybe less? I physically pulled the IAC plunger out and that provides enough air to raise idle to above 3,000. An emprical test that was a bit exciting:eek: I wished I'd had the log on.
The Fbody throttlebody only has the minimum stop position screw. I've adjusted it to prevent the idle from dropping too low so as not to ask too much of the IAC per Jesse's instructions which make a lot of sense.

It looks like I'll end up buying the tuning license for EFILive so I can workout the tuning issues. Which is a great solution if it works. I just didn't want to spend another $500 at this time, but if that's what it takes fine. Hopefully I can get a feal for if I'm heading in the right direction. I don't mind spending the money I just don't want to waste it!:frown:

I know somebody in here can get me in the right direction.:cheers:

[ScarabEpic22]

Since you have a V1, I dont think the upgrade to Tune is that much, maybe if you upgrade to a V2 unit it is but to just upgrade your V1 shouldnt be that much.

I was just throwing the IAC part out there, I have no real world experience with these engines and am just going off what Ive learned about them from poking about here and on other websites. I think you should be able to fix it relatively easily if you do get the tune part, should just be a few tweaks here and there to the Idle portion of your tune. Plus you can do an AutoVE and dial in your engine perfectly. :D

And I understand your concern about wasting $$$, Im in college so money is extremely tight for me right now!

[ssheets]

What I mean by repeatability. Notice TP=0% and IAC count saws from 199-310 and ad idle goes from 2,200-3,300 :Eyecrazy: I think this was from engaging and disengaging the clutch after it was driven to high idle from turning the AC on.
http://i238.photobucket.com/albums/ff281/500hpss/EFI%20Live/Snapshot006.jpg

[joecar]

ssheets,

I'm not very good at cam/idle problems, but see if this thread contains anything that will help your case:
showthread.php?t=4661 (http://forum.efilive.com/showthread.php?t=4661)

[1Hotbird]

I think if you present this data to Jesse at Waitformeperformance he would have to take a second look at the tune!!!!! Maybe it was just a Honest mistake or something that he diden't notice? Maybe even a Bad PCM????

Hopefully you get someone to chime in that can help! Good Luck

[1Hotbird]

I'm Guessing your problem is here! Would be interesting to see your tune!!

http://i134.photobucket.com/albums/q84/1Hotbird/Iac2.jpg

[ssheets]

I'm Guessing your problem is here! Would be interesting to see your tune!!

http://i134.photobucket.com/albums/q84/1Hotbird/Iac2.jpg
Yeah, hopefully I can figure it out by the time the snow melts.:D

This got me thinking. I installed the cam early Dec. Wheil test driving ghe car it was cold, but dry. It was when I'd turn on the defroster or AC that I have the idle issues. I didn't put two and two tegether until I had either severe cold so I had to use the defroster and then when it warmed up enough to turn on the AC it all made sense (with the help of the EFI Logs). I don't remember if the AC or Defrost was on when we test drove it initially? It still fallows the wait4me tuned PCM, but the wait4me tunes run better generally speaking.

[ssheets]

Well I put the OEM PCM with a mildly tuned Predator program and the problem is gone. It doesn't idle quite as well under hot re-start, but overall it runs a lot better. It feels like it makes more power with the Predator tune too. Here's an idle log with the Predator tune.

[ssheets]

Thanks to Doc I think I'm on to something.

Proper setup of the TB is critical. One thing that I stated in this thread was my IAC step counts. My hot idle (176*+F) was around 100. I've opened the blade up more and performed proper TPS resets to get that down in the 20-30s. I might be too far? The idle is great on the Predator tune and the wait4me tune seems much better. It will search once and take a trip up to 200-310 (2,000RPM-3,000RPM) and then settle down and behave normal.

It snowed about a foot last night so I can't drive it to road test it, but it's looking better.

I also traced out more of the vacuum lines (again, thanks Doc) from the horn to the firewall. I can't break the little check valve/tee by the PCM to isolate it, but it looks good. If I break it open I may really break it so I'll leave it alone for now. Besides, MAP doesn't support a vacuum leak and TB/IAC setup seems to be making a big difference.

Now, here's the biggy. Jesse mentioned this up front and had he been in proximity of the car instead of a hurried phone call tune I'm sure he would have defined this better. For the price Jesse charges he's still the hands down best value out there...with a little element of you get what you pay for.:Eyecrazy:

[1Hotbird]

Hey I was just wondering if you opened your throttle blade more to get the Counts down; When the computer opens the Iac to 310 again wont that run your RPMs That much higher??? Or will this stop the Iac from opening up that much???

[ssheets]

Hey I was just wondering if you opened your throttle blade more to get the Counts down; When the computer opens the Iac to 310 again wont that run your RPMs That much higher??? Or will this stop the Iac from opening up that much???
I was just wondering about that. I haven't been able to do much testing, but what I have so far I'll attach in the log file.

Yes, at 199 IAC. You'll see it now supports a 2,800RPM. At 310 IAC it doesn't seem to gain much more than the 3,200RPM though. Just as you figured, with more throttle plate airflow the IAC has a greater net gross effect.

I doen's stay at high idle now though. If you look at frames 575 to 675 you can see the event caused by AC on and a little encouragement from the throttle. Fram 766 is when the AC is turned off. It has a similar, but shorter duration idle event.

[edited for clarity];) ;)

http://i238.photobucket.com/albums/ff281/500hpss/Jan%20Snow/aDSC_3208.jpg