Idle Speed Problem
After 3 days of digging through the web and forums, im stuck. I'm a carb guy, so this is a learning experience for sure. I'm having the issue where the idle seems sluggish to drop and idles way too high. I have a SCT Tuner and a tune loaded that has the car running like a top now. The issue im having is that its idling between 1200-1450. It doesnt surge it just seems to "choose" one of those to idle at every time it settles back into idle.
Here is some history of the car. The guy i bought it off of has removed the EGR (turned off in tune), Evap (dont know why...), full exhaust long tube headers to tail pipes with no cats. Rear O2s turned off in tune, It has an Air Raid CAI, 78MM BBK Throttle Body, AC Delete and 24lb injectors. The car was an automatic car that has been converted to a manual.
In the SCT i set Idle Neu and Idle Drv to 820. I ran the tune and changed the RPM up or down one setting a few times thinking maybe it didnt program quite right because when it wasnt running right i had the idle at 1100 to keep it idling.
I installed a brand new IAC because i didnt like the look of the old one inside and that solved the fact the car wouldnt idle lower than 1100 and solved the cold start issue i was having where i would have to hold the gas for about 30 seconds and then the car would ramp up and settle down and idle on its own.
I dont have access to a scan tool at the minute but the SCT gives codes and some data. I dont know how to read the TPS in the SCT (will have to search up a user manual for the SF3/X3). The Desired Idle shows right in the data but the computer doesnt ever throw an over idle code. I replaced the TPS and tried adjusting it with no change thinking the tps was telling the car i was on the gas a bit.
I sprayed intake cleaner all over the top of the engine multiple times and no change to idle. I installed a new PCV and inspected all hoses. I went through and removed any loose vacuum leads that were capped to eliminate as much line as possible that could have a leak.
Thinking maybe TPS i installed a new one. I dont know how to read its data right from the SCT either, its showing tp_v 138 at idle and climbs as you push the throttle (supposed to be between 0v and 1v supposedly so is this 0.138v?)
I changed spark plugs, did oil change, ran some redline injector cleaner and cleaned out the throttle body.
I then looked to the manual adjustment on the throttle body and adjusted it until the plates where completely closed and then cracked them back open about 1/4 of a turn with no change. I then unplugged the IAC and it immediately stalled (thinking this is good because a significant vacuum leak would of let it still let it run?). I set the idle as low as i could without the car stalling manually. at about 600RPM it would surge 600-750 so i left it there. I shut the car off and unhooked the negative from battery for 10 mins with lights on. Started it up and it idled at 2000 for 5 minutes (engine was at operating temp). I unplugged the IAC and the car sputtered and stalled. I started the car and it went back to surging 600-750. When i plugged the IAC back in you could hear it sucking air like mad and the idle ramp back up to 2000rpm. It sounded like sticking your thumb over most of a vacuum cleaner nozzle. I then set the plates closed manually and opened them just enough to not get stuck when closing and it was back to 1250 rpm with a desired of 820 at that point.
In case i introduced a vacuum leak while messing around i again sprayed every inch of the top of the motor down liberally with intake cleaner and no change in RPM. Since all of this it has run for about 45 minutes and done quite a few stop start cycles at stop signs and again this morning idles at about 1200.
I started looking over if any hoses were hooked to the wrong places and it looks fine. I did notice that if i unhooked the hose going to the drivers valve cover the idle would drop about 100RPM and pick back up when i hooked it back up. I also pulled the PCV and plugged it with my finger to see if it would change anything and it did not.
I might have missed a few other steps i took but i pretty much followed any and all high idle "fixes" i could find between forums and youtube videos. Any help would be appreciated.