ive had an idle problem ( car is automatic) for some time now that is steadily getting worse. heres the whole deal sry in advance if its a bit too read but i need help. never had any problem untill after i installed my bbk intake manifold and a summit 85mm throttle body. i used felpro gaskets on the intake and i i reused the sensors from my old throttle body. my car started having a very slight miss at idle but nothing at all to worry. a month went by and i did long tube headers with AIR delete, ( re used stock o2 and car is still not tuned) soon after my idle problem got worse and worse by the day, and got really bad at cold starts. i would start the car and it would almost die, i would have to rev it just to get it to settle into a normal pattern. it would take a min to warm up and idle correctly. then got worse and one day in the rain my car started mifireing so bad i could not go above 20mph and i limped it home, blinking ses light. i replaced the o2 sensors and car ran fine. now my idle problem is back and got progressively worse as it did before, same very rough idle on start, today i started it and watched the rpm go from 400 then jump to 700 then go back down and up till i reved it and it settled on 500. at stoplights car will noticebly miss at idle and it gets so bad i think it will die on me sometimes, i will have to hold down the gas pedal at stoplights to keep it going. i replaced the o2 again this time with denso and no change. ive cleaned the MAF and no change. i unplugged the MAF during idle and it seemed to get a little better and get worse as i plugged it back in but it was so slight i could not be sure. heres my guesses and looking for input from you guys. car is only throwing the AIR delete codes and the no cats codes you get from doing lt's.
car idles at about 600 in park and in drive but at stop idles at 500 but dips low almost to 450

MAF sensor?

bad idle air controller? or the stock IAC not good for my bigger aftermarket TB? ( this one is what im leaning towards the most)

engine coolant temp sensor ( noticed the wires going into it are bare and exposed and seem to be barely hanging on to the sensor)

or just really really need a tune for the lt install and the air delete

 

update i just went out to my car and let it idle and unplugged the IAC and the was no change what so ever, you could still hear and see the motor miss and shudder and when i plugged it back in there was no change, no sounds change no change in shuddering, i know you can check a MAF on some cars this way but can you check an IAC this way on ls1's? does this mean my IAC is bad or nto good for an aftermarket 85mm tb?

 

I had similar problems when the engine coolant sensor was cracked.I would check to see if it broken,plugged in all the way or corroded .You may have to do a IAC relearn too.

 

i ordered a eldebrock IAC and engine coolant sensor from summit. below is a pic of my current ECT. i cut a spare connector that fits off the harness that was left over from my AIR delete. ill do the wire repair when i go to put the new sensor in. i unplugged my sensor and tried to start the car and it would not start so i know the ECT is working but it very well may be failing. what is an IAC relearn tho? is this the same as disconn the battery for 30 min and reconnecting?

am i correct in my reasoning so far?

 

Vaccum leaks can cause this jumping/serging rpm. Kinda like gasping for air. I had a small pin size hole in my pcv line and my rpms would serge, drop to 350-400 and almost stalled a couple times. Had to hold down the gas in neutral at stop lights. Check all your lines or listen for a sharp sucking (mine sound like it was hissing). If that fails their always vaccum can spray, sprays out a very fine mist that will suck right into the leak. just my .02

 

i did have a large hole in my pcv valve and noticed it when i did my intake. replaced it with some hose during the install.

 

You changed to a larger throttle body and a different intake. Did you ever get the car tuned? If not, you can't expect it to run right.

 

sounds like a vaccum leak and leaning mostly to you needing a tune, I gutted the cats on mine and it was almost cutting off at the lights. the rear O2's needed to be deleated and the computer needed to recognize all the aftermarket stuff put on it. See if you can get a tune by Frost

 

heres whats it got with no tune
lid
ssra
85mm tb
bbk intake
bbk long tubes
3" cutout
ngks and msd wires
AIR delete
front o2 sensors are denso rear o2 are stock from 2001

so you are saying that even though this isnt a whole lot that it can mess with the car?
i do need the cats codes tuned out, and the AIR system tuned out and the rear o2's tuned out as well. if its still real bad after i swap the IAC and OCT then i will tune right away. i was afraid to tune it bcuz it was running so shitty that i would make it a pain in the *** on my tuner

 

It's quite possible if you didn't secure the knock sensor wires to the valley cover that wires got pinched between the intake and the passenger side head when you installed the BBK intake(I did). This could cause a slight vacuum leak and cause problems with the KS., and it would slowly get worse.

 

i had the exact same issue with my intake install but turns out it was O2s and slight pcv vacuum leak...if you said your car wont do well in open loop am thinking open loop sensors or some of the coils that the pcm cant detect for some reason...id unplug the O2s and let it idle for a while, if it clears then you found your problem. if not double check MAP and MAF sensor for leaks or try to borrow a maf from a friend and see how it goes. provided you installed everything correctly. i HATE when this happens! good luck.

 

omarrakeen, glad to hear you finally got it fixed !

 

so i installed the new IAC and im not sure if its worse or better. the problem is so spotty its ridiculous.

 

your car is in limp mode that also happen to my ss when i put in LTS w/o a tune and burnt out my two front o2s and it felt like i was running on 4 cylinders and the car was shaking like crazy you maybe just need a tune your air to fuel ratio has to be off due to all the mods

 

thanks i lost my mind over this lol i had no idea O2s could cause all this smoke, shake and other crap!

 

I had similar issues. Make sure your throttle body gasket has a hole in it for the IAC. When I installed my BBK intake the gasket it came with sealed the hole on the back of the throttle body that the IAC feeds through. If your gasket is the same way just cut a hole out for the IAC it is should fix the problem.