infamous high idle after throttle clean possible fix
12-24-2018, 07:48 PM
#28
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With the battery disconnected, you put your key into the on position and leave it for 5 minutes. Then off for 30 seconds and repeat 3x.
I've seen this on other forums (including another cobalt forum) and some people reported success. Think of it like resetting a router/modem. You are essentially resetting the computer in your car. What this does is clears the remaining electricity in the capacitors and relays and thus no energy, no memory.
I would call another mechanic and ask if they have a Tach 2 machine that has idle relearn capabilities as a backup plan.
I've seen this on other forums (including another cobalt forum) and some people reported success. Think of it like resetting a router/modem. You are essentially resetting the computer in your car. What this does is clears the remaining electricity in the capacitors and relays and thus no energy, no memory.
I would call another mechanic and ask if they have a Tach 2 machine that has idle relearn capabilities as a backup plan.
03-15-2019, 09:43 PM
#31
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07-11-2019, 09:08 AM
#32
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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.
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.
Tried this, this morning. So far so good, will see if it sticks
03-02-2020, 06:07 PM
#34
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Dealing with this exact issue on my 2010 Cobalt
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.
thinking about getting another throttle bottle from a junk yard and just not cleaning it. Its either that or pay for a dealer to flash ecm or buy a new throttle body and still might have to flash the ecm. Idk sucks I just wanted to help get better performance and now my car is worse.
03-03-2020, 12:34 PM
#35
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Same thing happening to me on my 2010 2.2 base model automatic. Have tried the relearn process, unhooked battery for 10+ minutes, out car in on position for 10 mins and then tried relearn process. Also drove car for 2 hours in and off the interstate. Still same issue, and really sucks when you tap gas with it in park and it jumps to 3k RPMs stays...
thinking about getting another throttle bottle from a junk yard and just not cleaning it. Its either that or pay for a dealer to flash ecm or buy a new throttle body and still might have to flash the ecm. Idk sucks I just wanted to help get better performance and now my car is worse.
thinking about getting another throttle bottle from a junk yard and just not cleaning it. Its either that or pay for a dealer to flash ecm or buy a new throttle body and still might have to flash the ecm. Idk sucks I just wanted to help get better performance and now my car is worse.
04-22-2020, 11:13 AM
#36
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not always "on it's own"
I followed every different suggestion in this thread (and every other thread I could find) and nothing worked. After putting more than 1k miles on my car over the course of a month, doing every suggestion here, I finally broke down and went to my dad's shop. He's a few hour drive away, so I don't make the trip often. He checked with the Tech 2 and there was no relearn procedure for it from GM. I was afraid he would have to completely re-flash the computer. He was able to use the scan tool to take command of the engine and bring the RPMs down to normal (confirming the throttle body wasn't damaged), but after disconnecting the scan tool and shutting off the car it would go right back to high idle. We repeated this several times with the same failed results. In the middle of it all we even switched to a Snap On, because the Tech 2 had worn out connectors and kept dropping signal, and still go the same results. We found the fix by accident. He wanted to see if the drivability symptoms (I had RPM spike and hang when shifting - it's a 5 speed) would go away while the scan tool was still hooked up forcing a lower curb idle. Turns out the fix is to command the RPMs down to around 700 with any scan too capable of controlling RPMs, then drive it for a mile or more at speeds above 45. Since doing that I have repeated several drive cycles and it's still working great. I'll update if anything changes.
Edit: It turns out that this fix works, but must be done with the AC and Defrost on and off (so 3 drives). If I turn on my defrost or AC now the idle tries going back to 2k. I'll try to confirm this in the coming weeks, but for now i'll just do my best to avoid using either.
Edit: It turns out that this fix works, but must be done with the AC and Defrost on and off (so 3 drives). If I turn on my defrost or AC now the idle tries going back to 2k. I'll try to confirm this in the coming weeks, but for now i'll just do my best to avoid using either.
Last edited by Thermos; 04-23-2020 at 11:55 AM. Reason: new symptoms
02-23-2023, 08:57 AM
#37
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did you get the tb and sc tuned to the car?bc you have to get it tuned to the car
02-23-2023, 09:01 AM
#38
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My car keeps idling at abt 1700 rpm and i bought a brand new tb and everything i took the sensor out and disconnected the map sensor and all failed but when i slip the clutch a few times it goes back dow to abt 500-800 rpm normal idle speeds but if u give it gas it goes back up and stays and all i did was clean the tb any suggestions?
02-28-2023, 11:35 PM
#39
My car keeps idling at abt 1700 rpm and i bought a brand new tb and everything i took the sensor out and disconnected the map sensor and all failed but when i slip the clutch a few times it goes back dow to abt 500-800 rpm normal idle speeds but if u give it gas it goes back up and stays and all i did was clean the tb any suggestions?
if you clean the tb and move the plate, you might need to do a relearn. This is from what have read.
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