ENRKyle20

Im almost positive this is not a IAC issue, but a tune issue or some other problem. I cant find a good position for the throttle plates as on a cold start if I set the plates to a position where it idles and the IAC is around 110 then once the engine is warm the IAC is basically closed the the idle is about 1500rpm or more. If I set it with a warm engine it will not idle on its own until its warm. I did disassemble and clean the IAC unit and I did the drill mod (I wonder if that could be causing an issue..hmm).

So I know its a lot to ask of someone who is not familiar with my engine or tune but what do you think it could be?

I tried speed density mode to see if maybe my MAF was not working properly but it did not make a difference. Its not a open loop/ close loop problem it only depends on temp - I did replace the IAT sensor and the coolant temp sensor (front and side of engine)

min injector pulse width is 1.007

my target idle is between 850 and 950 depending on temp.

HERE is my tune if you want to have a look. Thanks so much.

bobdec

Which drill mod.. Opening IAC hole in TB to match Idle Air port in the intake - OR - Drilling hole in the butterfly blade(s) ? Can you confirm there are no channels in the TB that will leak IAC air into the main openings (s/b solid metal, solid gasket, between the IAC hole and the two TB main openings) .
Your tune has idle at 800 from 115*F and up. So if you get to operating temp in closed loop (215 seconds running) and look at your TPS voltage and IAC what do they read. If you're ideling at 850-900 then you may be controlling idle with TB opening air not IAC air.

TPS s/b .50 to .70 volts and IAC s/b between 20 and 50 at 800 RPM. It's a balancing act between TPS voltage, IAC and maybe having to slot the TPS mounting holes to get everything alligned. Not familiar with a LE2.5 setup, what cam specs are in it ?
Can you post a log or .csv of your idle

This hread has some sample pics and info of IAC port to TB opening problems..http://ls1tech.com/forums/lt1-lt4-mo...an-oem-tb.html

ENRKyle20

Thank yo so much for the response and the help.

*Im willing to bed a good portion of my issue is due to the aftermarket Professional Products 69702 GM LT1 58 MM Throttle Body and/or the drill mod*


The drill mod I was referring to was drilling a small bleed hole (like a stock TB has) to let a small amount of air pass the IAC at any time to instead of cracking the throttle blades [no drilling butterfly blade(s) either], then I also put a piece of pipe in the IAC outlet to keep air out of the main plenum and only feed the idle air passages in the head. Since i have a well fit pipe in the IAC port going into the intake I wouldn't think it could leak air into the main plenum - IF it does it would have to be a very small amount. I could take it apart and just make sure everything is good in that department.

TPS is .59V when closed

I got it up to temp and idle was way to high. I closed the blades completely and it was a bit low, I may need to drill the hole a little larger, but I need to take care of my fueling issues before i do that, its speratic now, sometimes it needs lot of throttle to idle, sometimes it needs none. Its because my fueling is pig rich it looks like. I need to take some more time on my tune before I look to deeply into this idle issue. my fueling is all over the board. I think i need to change my injector constant to get my fueling closer to normal. (my airflow is all zeros because im running speed density) here is a freescan log once up to temp: HERE




And cold (I did close the blades a bit after this scan seeing my tps volts kinda high and idle to high)HERE COLD



Here is the cam specs - a fairly intense cam so I know the idle will never be perfect.



Currently I have just two long straight pipes with chreey bombs coming off the header, i bet air is getting sucked back in and messing with the o2 sensors and making fuel go wacky. I think i need to turn up min temp for closed loop to keep it in open loop, and using injector constant to get fuel even and correct then see where the idle is, do you agree?

slick1hunting

If I remember correct when I modded my tb you can go too far with the tube and it either obstructs the iac valve opening or something else that limits the flow. I had to shorten mine upon closer inspection. I also did the through hole mod and should have waited because my iac valve was either damaged by me or on its last legs and drilled too large and later had to sleeve that hole to get iac counts were they needed. I would take a look at your tube and be sure its not too long(I think I removed the iac valve body to see but dont remember now). My tb is a tpis and I also have a n2o plate behind it which made for a little extra work.


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ENRKyle20

Ahh very good tip. I didnt think of how long the tube was. Im going to pull it apart and take another look. I did it a long time ago - now that I understand it better its a good idea to give it another go. How did you know your IAC was bad or on its last leg? did it get lazy to a point you can tell on a scantool?

slick1hunting

the iac valve was very inconsistant on the logs. It would act like a sticking throttle most of the time and high idle at like 1700+ at a stop and sometimes working throttle would get it to drop. Sometimes it would want to try an idle at 400ish or less and I would have to work throttle at a stop. It progressively got worse. I checked the resistance of its coils via shoebox instuctions and they checked out. I even lubed it up knowing I was ready to just buy a new one and that did help it operate better for a very short time. Then it was next to undrivable. I also did the reset procedure (shoebox instructions several times too). The big thing was how inconsitant the count was while logging(with very similar operating parameters-rpm, temp,etc.). I also found the acdelco online for half of what dealer was wanting for one. It still worked but it wouldnt open and close to correct consistant locations. I very well may have hurt it on transplant and cleaning it. The counts ended up being considerably off from what the average was when it would function semi ok. I also had fueling issues at the same time but mine was car was lean and wanted to add a bunch of fuel. My widebands confirmed that.


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ENRKyle20

ok good info. I will pay attention to what mine is doing, I may have a lazy IAC as well. Thank you