infamous high idle after throttle clean possible fix
 

edit - this is for an 07 ss/na

so after getting the high idle after cleaning my throttle body and spending a week determined to figure out why all of a sudden it does it. i've come to 2 conclusions.

1. upon cleaning the throttle body the computer for whatever reason is unable to correctly relearn the idle position. even though the throttle body is operating correctly and everything is in working order and no vacuum leaks. upon further inspection the commanded throttle state is at 20% which should be at 6% for an at rest idle.

2. reflashing the ecm with the same calibration does not overwrite and correct the glitch with the ecm. as i have the grey molded injectors, and there are 2 differen't calibrations one for grey molded and one for blue molded injectors.

now as i have access to a gm shop and am able to reflash my computer at will (used to work for gm and still have 2 brothers that work for gm). and when you stump 4 technicians, a driveability tech of 30 years and a mechanical engineer on why it is idling high when it shouldn't. you know its something weird.

so what i decided to do is load the blue molded calibrations on my car and directly after that calibration was complete reloaded the correct calibration back on to my ecm.

low and behold my car is now fixed without replacing any unnecessary parts.
now if anyone out there can confirm this as a replicable fix i think this would keep alot of people from wasting money and time on trying to figure this out.

also explains why replacing the ecm worked because a fresh calibration was being written to the computer and not trying to be overwritten.

p.s.

even though i'm not a technician, i'm still quite handy when it comes to cars in terms of diagnosing. but the entire thing was blamed on me for how i cleaned my throttle body and was told that i screwed up the throttle body somehow.

how high of an idle? i had the infamous bouncing rpms when came to a stop in my 2.0, cleaned my tb and it never bounced again. it did seems though that the idle rpm was a little high at first. maybe 500rpm i didn't worry about it though.

no mine was the one where it would shoot up to 3000rpm and stay there and might come back down to 1500 but would never idle properly and always wanted to speed up even though your foot wasn't on the gas pedal. this was is more for the 2.4's and possibly the 2.2's then the 2.0's.

mine still does this despite a tb clean. its only 1 bounce though

Ya the one bounce up to 1500rpm or lower is normal. But constantly revving to between 2000 and 3000rpm is not.

But apparently no other n/a cobalt is having this issue anymore despite the numerous threads I found about people with this issue and no one else being able to fix it.

As I said in the OP that of course replacing the ecu will fix the problem because its a fresh load of the calibration but not everyone is within warranty. So this is a relatively cheap fix compared to an ecu replacement.

And trust me there is no other cause of this. Tried new throttle, new maf, checked the entire pcv system, checked all possible causes of a vacuum leak.

I just read your post about this problem. I cleaned the TB with TB cleaner and I now have the exact same problem you had. Here's a twist though...

I drove it to work and back - about a 35 mile round trip. The idle was bouncing at times up to 2500 or even higher. Never below 1500.

I doused the TB pretty good with TB cleaner and yes, I moved the butterfly a LOT during cleaning (GASP!!!)

It makes absolutely no sense that the TB would lose its calibration by moving the butterfly. If the POS is that sensitive to being messed with, its incredibly poorly engineered.

So here's the interesting part... I started it up and pulled the air box off while it was running. It idled down to about 700RPM and chugged a little bit. I put it back on... It settled right down to 850RPM and purred like a kitten! I shut it off again and restarted it. 850RPM - SWEET! I took it for a drive around the block and everything was perfect. I even shut it off and restarted it along the way - Perfect 850 idle speed. Then I took it home, shut it off and let it sit for about 10 minutes. Restarted it... You guessed it. 1500 RPM idle and all F'd up again!

Pulled the the hose off the air cleaner box - Idled right back down where it should be! The above sequence can be repeated over and over. It's as if the ECU finds its brain again when you pull the airbox off the TB or disconnect the air cleaner box (and MAF sensor of course - Or whatever form of air metering this car has). It sort of does some form of recalibration on the fly and it sticks for a time but doesn't last.

This is totally bizarre. It makes no sense that the ECU would lost its mind so easily. Is the only solution to bring this POS in to GM and get them to load a different set of instructions into the ECU? Really?

I was tossing codes on a different car and cleaned the throttle body. A mechanic told me if the idle issues are worse afterwards to turn the car off and wait about 30 sec. Then key on(not start) for 30 sec and key off for 30 sec. Then start the car. Repeat if necessary. He claimed this has worked on many different vehicles that have gone through his shop. It can run through a calibration apparently. I didnt need to do this but thought I'd share. You can hear the throttle body going through motions on many cars after a few seconds of being turned off. Not sure if this is true or will help at all, but worth a try.

Tried that no fix...lol

I removed TB and sprayed with TB cleaner, not touching butterfly and I have the idle issue.
Tried most tricks none worked yet, ecu reflash, ign on off on, bat disconnect.
Guess I'll try the driving part now.........

Did you get it worked out yet?

No Sir,
It is getting better.......
It is still searching for idle a little, but
way better than its was days ago.
I guess just keep driving her.

Did you guys remove power from the car before unplugging sensors? I don't think it would make a difference, just throwing it out there.

Also, did you guys spray the crap out of the TB or spray a towel and then wipe down? Just wondering if the spray got into the electronics or some crap.

Power always removed before un/pluging electronics.

I sprayed the TB with TB cleaner and no electronics got sprayed.
I did not touch the TB butterfly other than spray.

It is getting better, but still has its bad drive cycles once in a while,
high rev on start up, hanging high when cruising and lift foot off the throttle.

I guess my car lost its mind today, it was getting better.
all day back to the 2500 rpm at start up and then drop to 1500..... :(

Yeah, mine did the s as m we r thing after a clean. Just let it work itself out. She is all good now.

I need to clean mine, but I am scared :lol:

I have this issue .. it started when I cleaned my throttle body.. originally my issue was a p0171 code for my cat my uncle (gm mechanic) said that was causing my issue and to have the vehicle tuned I did that and the issue went away.. with the rough winter we had here in pa I ended up needing a battery and now the issue is back .. but my car is now idling soo low it caused a miss fire.. I replaced plugs and coil packs.. has any one else recieved a missfire from this rpm issue

mine is now almost back to normal after weeks of this issue.

just hope she doesn't loose her mind again.

Thank you! It works. This LE5 motor is so hard to get to idle right again, I reprogrammed with the normal method and had no success. Battery disconnect with no success. Programed using your blue injector and then back to the correct gray. It RESET the Idle Cells. This LE5 is now idling correctly while driving, shifting "manual" between gears. YOU ARE A LIFE SAVER!

I've been reading a lot of different forums about this same problem as I am having it right now. One question I can't seem to find the answer to is, are you guys all getting the check engine light with this? When you get your car to idle normally, does it go away? I had it all good, engine light gone for all of about two hours... Can't seem to get it right.

I just supercharged my car and it idles at 2700-3000 rpms and drives by itself. I don't know what's wrong. We checked for leaks and can't find one. I'm getting throttle body codes however. Any idea?

did you wire the throttle body wrong?

Didn't wire the throttle body. It was plug and play. Had an adapter.

2.4 2800 Idle
 

Im gonna raise this post from the dead because recently I cleaned my Tb while doing a thermostat replacement. I was already into it so I figured why not. Aand I made a boo boo. I opened the Tb with my fingers to clean it before I read to strictly not do that lol. Well now in the morning the first start up of the day it will idle down to id say about 760rpm but as soon as you touch the gas pedal back right up to 2800-3000 rpm and tries to do 40-45mph by itself. I took it to the dealership hoping it just needed to be recalibrated but was told by the lead service tech that there is no recalibration sequence on this car. But made me aware that transitioning from 30% to 40% idle that my Tb clicked very loudly and only at that percentage. So I'm desperately hoping someone figured this out because I cant afford a new Tb at the moment and my car is eating gas idling like this.
The car is a 2007 Pontiac G5 GT 2.4L TIA...

Tach 2 OBD2 tablets have the idle reset function, but those are like $800 + updates.

When I cleaned my TB, I drove it like a maniac for a week and it finally settled. There are other threads that cover the details, but you can google them.

One way was to disconnect the battery and power cycle the system. Somebody else swapped TBs, and others just kept driving (I went way out in the rural areas and just ripped on the throttle).

Oh trust me I have practically beat the hell out of my car. This has been going on for the past month. I drive it every day and it hasn't showed no signs of helping. Ive unhooked my batt and let it sit for an hour, tried the whole key on/off start up for 3 mins, removed throttle body to inspect it and found nothing wrong. I put $30 in gas(which filled it up) and only drove 80 miles according to my Dic and was already down to a quarter tank. My heads about to explode with this one. I have never had a vehicle with a problem that I cant do absolutely nothing about. I've went 0-100mph WOT every gear(its an auto) more times then I can count, plenty of decelerations from high speeds and still nothing. The stealership quoted me $515 bucks for a new throttle body and I said over my dead body lol. Im screwed. I guess new Tb it is