Idle Troubles!!! Help
09-14-2012, 03:55 PM
#1
Thread Starter
Join Date: Sep 2012
Location: MN
Posts: 18
Idle Troubles!!! Help
Hey, new to this forum, but I have looked at almost all threads that cover my car's problem and have not solved the problem... Here's what's goin on- About 4 months ago, I got my 2000 Mustang GT and was sitting at a stoplight with the AC on and I noticed that the RPM's would jump up and down about every 10 seconds from about 800 up to 1100-1200 and back down. It didn't really bother me at the time but as the new car feeling wore off, it started getting annoying.
It also began getting worse as the car would idle down to the point where it would almost die, then fly back up. Sometimes it would die as well. Then about 3 weeks ago, I was driving to town and noticed that the car lost all of its power and started backfiring. Found that out to be the O2 sensor.
So, I put one new sensor in and fixed that and also seemed to help the idling problem for about a day or two.
Then, about a week later, the idling started getting worse, it would not idle lower than 1100 RPM's when warm (it would still idle up and down, but only with the AC on). SO, I looked at some forums and found out the the most common problem is IAC valve. Replaced that and seemed to help again for a couple days, then it started doing it again.
So, I did more searching and found that the O2 sensor could cause this. I got my code reader and it showed the code P0155(02 Sensor malfunction). I went and bought ANOTHER O2 sensor for the other side and installed it... That helped for a day and now the car will still not idle down under 1000 RPM's(only when it's warm though) and the code is back!!!
ALSO, after every step, I would unhook the battery and let the computer reset, sometimes for 30 mins.
Thanks for looking and sorry for the length.
It also began getting worse as the car would idle down to the point where it would almost die, then fly back up. Sometimes it would die as well. Then about 3 weeks ago, I was driving to town and noticed that the car lost all of its power and started backfiring. Found that out to be the O2 sensor.
So, I put one new sensor in and fixed that and also seemed to help the idling problem for about a day or two.
Then, about a week later, the idling started getting worse, it would not idle lower than 1100 RPM's when warm (it would still idle up and down, but only with the AC on). SO, I looked at some forums and found out the the most common problem is IAC valve. Replaced that and seemed to help again for a couple days, then it started doing it again.
So, I did more searching and found that the O2 sensor could cause this. I got my code reader and it showed the code P0155(02 Sensor malfunction). I went and bought ANOTHER O2 sensor for the other side and installed it... That helped for a day and now the car will still not idle down under 1000 RPM's(only when it's warm though) and the code is back!!!
ALSO, after every step, I would unhook the battery and let the computer reset, sometimes for 30 mins. Thanks for looking and sorry for the length.
Last edited by Fordman131; 09-23-2012 at 08:39 PM.
09-14-2012, 05:12 PM
#2
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
It is not possible to adjust the idle speed without a tuner, the PCM will do whatever it can to keep the idle speed at whatever it has been programmed to be.
You can however, and should, check the throttle stop screw setting--here is how to do that.
Cleaning the TB is not advised unless it is horribly filthy dirty, which likely means you have far more serious problems than you suspect.
(see the second caution)
If you insist then reset the stop screw after doing so.
There is no need to keep the battery disconnected for more than 5-7 minutes, also every time you do disconnect it your are clearing the KAM (Keep Alive Memory), a RAM module in which the PCM stores its learned values--things like idle air and fuel trim values.
It (the PCM) therefore will have to "start all over again" learning those parameters.
Adjust the stop screw first, then drive it 25 miles or more and see what happens. Make sure the plugs and COP boots are OK...
One last comment, put some paragraph breaks in your posts so that people will bother to read them:
See how much easier that is to read...
You can however, and should, check the throttle stop screw setting--here is how to do that.
Cleaning the TB is not advised unless it is horribly filthy dirty, which likely means you have far more serious problems than you suspect.
(see the second caution)
If you insist then reset the stop screw after doing so.
There is no need to keep the battery disconnected for more than 5-7 minutes, also every time you do disconnect it your are clearing the KAM (Keep Alive Memory), a RAM module in which the PCM stores its learned values--things like idle air and fuel trim values.
It (the PCM) therefore will have to "start all over again" learning those parameters.
Adjust the stop screw first, then drive it 25 miles or more and see what happens. Make sure the plugs and COP boots are OK...
One last comment, put some paragraph breaks in your posts so that people will bother to read them:
Hey, new to this forum, but I have looked at almost all threads that cover my car's problem and have not solved the problem...
Here's what's goin on- About 4 months ago, I got my 2000 Mustang GT and was sitting at a stoplight with the AC on and I noticed that the RPM's would jump up and down about every 10 seconds from about 800 up to 1100-1200 and back down. It didn't really bother me at the time but as the new car feeling wore off, it started getting annoying.
It also began getting worse as the car would idle down to the point where it would almost die, then fly back up. Sometimes it would die as well. Then about 3 weeks ago, I was driving to town and noticed that the car lost all of its power and started backfiring. Found that out to be the O2 sensor.
So, I put one new sensor in and fixed that and also seemed to help the idling problem for about a day or two. Then, about a week later, the idling started getting worse, it would not idle lower than 1100 RPM's when warm (it would still idle up and down, but only with the AC on). SO, I looked at some forums and found out the the most common problem is IAC valve. Replaced that and seemed to help again for a couple days, then it started doing it again.
So, I did more searching and found that the O2 sensor could cause this. I got my code reader and it showed the code P0155(02 Sensor malfunction). I went and bought ANOTHER O2 sensor for the other side and installed it... That helped for a day and now the car will still not idle down under 1000 RPM's(only when it's warm though) and the code is back!!! ALSO, after every step, I would unhook the battery and let the computer reset, sometimes for 30 mins.
So, I figure my next step is to clean the throttle body and adjust the idle and hope for the best, but any input as to what the problem could be would be greatly appreciated!!!
Thanks for looking and sorry for the length.
Here's what's goin on- About 4 months ago, I got my 2000 Mustang GT and was sitting at a stoplight with the AC on and I noticed that the RPM's would jump up and down about every 10 seconds from about 800 up to 1100-1200 and back down. It didn't really bother me at the time but as the new car feeling wore off, it started getting annoying.
It also began getting worse as the car would idle down to the point where it would almost die, then fly back up. Sometimes it would die as well. Then about 3 weeks ago, I was driving to town and noticed that the car lost all of its power and started backfiring. Found that out to be the O2 sensor.
So, I put one new sensor in and fixed that and also seemed to help the idling problem for about a day or two. Then, about a week later, the idling started getting worse, it would not idle lower than 1100 RPM's when warm (it would still idle up and down, but only with the AC on). SO, I looked at some forums and found out the the most common problem is IAC valve. Replaced that and seemed to help again for a couple days, then it started doing it again.
So, I did more searching and found that the O2 sensor could cause this. I got my code reader and it showed the code P0155(02 Sensor malfunction). I went and bought ANOTHER O2 sensor for the other side and installed it... That helped for a day and now the car will still not idle down under 1000 RPM's(only when it's warm though) and the code is back!!!
ALSO, after every step, I would unhook the battery and let the computer reset, sometimes for 30 mins. So, I figure my next step is to clean the throttle body and adjust the idle and hope for the best, but any input as to what the problem could be would be greatly appreciated!!!
Thanks for looking and sorry for the length.
09-16-2012, 01:06 PM
#4
Thread Starter
Join Date: Sep 2012
Location: MN
Posts: 18
Update- I ended up cleaning out the throttle body with TB cleaner. The rag was pretty dark afterwards, but it didn't help at all! I haven't checked the throttle screw yet, but I'm thinking about bringing the car to my friends place so he can throw the computer on it to figure this PIT out. I'll keep you updated with the progress as soon as I figure something more out about the surging RPM's. Thanks again!
09-19-2012, 09:21 PM
#7
Thread Starter
Join Date: Sep 2012
Location: MN
Posts: 18
Yeah, I had pulled some codes from the car yesterday saying the 02 sensors were indicating a lean condition. Hopefully that'll do the trick. Also, what does PCV stand for and where is it located? (I know, newbie question! Ha).
09-20-2012, 10:16 AM
#8
Join Date: Jun 2012
Location: Wisconsin
Posts: 12
PCV stands for: Positive Crankcase Ventilation. And it's located on the passenger side valve cover. Theres a small black plastic tube running from the front of the Throttle intake plenum to it. Not too hard to spot. Shouldn't cost you more than $3-6 depending on what brand you get. As far as swapping it, just pop the PCV outta the valve cover, remove the plastic tube and your ready to install the new one.
09-26-2012, 08:43 PM
#9
Thread Starter
Join Date: Sep 2012
Location: MN
Posts: 18
Update:
I did end up checking the PCV valve to see if it was loose, which it wasn't. So, then I finally got it over to my cousin's shop today... He hooked it up to his computer and figured out the bank 2 sensor 1 O2 sensor wasn't reading right at idle but would read right when he revved it up...
That led him to believe that it was a vacuum leak (which was my thought too). So, he sprayed break cleaner all around the hoses and injectors and nothing happened, meaning there was no vacuum leak...
Then, that led him to believe that there was a problem with the programing in the computer, so he unplugged the IAC and used his computer to set the idle and voila! The car idled flawlessly right at ~700 RPM's and the hanging RPM's vanished! It ran like that the entire way home until I shut it off, restarted it, and plugged the IAC back in (which was to be expected as it was only a temporary fix). The only thing was that I didn't get to see if it fixed the surging RPM's with the AC on; as he said the car would probably die if the AC was turned on.
In the end, he said I would probably end up having to bring it to the Ford dealer to have them reprogram the computer... So, that will probably end up being my next step... I'll keep you updated to see if this solves the problem or not. Thanks!
I did end up checking the PCV valve to see if it was loose, which it wasn't. So, then I finally got it over to my cousin's shop today... He hooked it up to his computer and figured out the bank 2 sensor 1 O2 sensor wasn't reading right at idle but would read right when he revved it up...
That led him to believe that it was a vacuum leak (which was my thought too). So, he sprayed break cleaner all around the hoses and injectors and nothing happened, meaning there was no vacuum leak...
Then, that led him to believe that there was a problem with the programing in the computer, so he unplugged the IAC and used his computer to set the idle and voila! The car idled flawlessly right at ~700 RPM's and the hanging RPM's vanished! It ran like that the entire way home until I shut it off, restarted it, and plugged the IAC back in (which was to be expected as it was only a temporary fix). The only thing was that I didn't get to see if it fixed the surging RPM's with the AC on; as he said the car would probably die if the AC was turned on.
In the end, he said I would probably end up having to bring it to the Ford dealer to have them reprogram the computer... So, that will probably end up being my next step... I'll keep you updated to see if this solves the problem or not. Thanks!