When in park car will keep hesitating like it wants to shut off sometimes.
Mar 16, 2022 at 7:04 AM
Low/rough idle
2008 CHEVROLET IMPALA
STARLORD1976
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Hi,
The most common cause of a low or rough idle is an engine vacuum leak. That is where I would start checking.
Here is a link that explains how it's done:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
If this is something you have already done or it yields no repair, then we need to check if there are diagnostic trouble codes, if there is an issue with fuel pressure, or if the idle air control valve is going bad or simply needs to be serviced.
The idle air control valve (IAC) is responsible for maintaining engine idle speed. If it fails, oftentimes the idle speed will fluctuate up and down, or stalling can occur.
Let me know if you are able to perform the vacuum test.
I will watch for your reply.
Take care,
Joe
The most common cause of a low or rough idle is an engine vacuum leak. That is where I would start checking.
Here is a link that explains how it's done:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
If this is something you have already done or it yields no repair, then we need to check if there are diagnostic trouble codes, if there is an issue with fuel pressure, or if the idle air control valve is going bad or simply needs to be serviced.
The idle air control valve (IAC) is responsible for maintaining engine idle speed. If it fails, oftentimes the idle speed will fluctuate up and down, or stalling can occur.
Let me know if you are able to perform the vacuum test.
I will watch for your reply.
Take care,
Joe
Mar 16, 2022 at 4:35 PM
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No codes, no leaks, and I’m not sure if my car has IAC. Valve?
Apr 2, 2022 at 1:22 PM
Hi,
I did a little research, and although the manual has specifications for an IAC, it doesn't show one. So, you may be correct.
If there are no engine vacuum leaks, I looked for an idle speed relearn procedure. I found it. There is one with a scan tool and one without. To add insult to injury, the one for doing without a scanner tells you to watch the scan tool. LOL
However, I don't feel the scan tool does anything but show the RPM speed. Do me a favor. Take a look through the attachments and see if they help change the speed.
I will watch for your reply.
Take care,
Joe
I did a little research, and although the manual has specifications for an IAC, it doesn't show one. So, you may be correct.
If there are no engine vacuum leaks, I looked for an idle speed relearn procedure. I found it. There is one with a scan tool and one without. To add insult to injury, the one for doing without a scanner tells you to watch the scan tool. LOL
However, I don't feel the scan tool does anything but show the RPM speed. Do me a favor. Take a look through the attachments and see if they help change the speed.
I will watch for your reply.
Take care,
Joe
Image (Click to enlarge)
Apr 2, 2022 at 9:06 PM
Tried it twice still didn’t help.
Apr 4, 2022 at 12:20 PM
Hi,
By chance, have you had a chance to check for vacuum leaks? Also, have you ever serviced the throttle body?
Here is a link that explains in general how it is done. Try this as well.
https://www.2carpros.com/articles/throttle-actuator-service
Let me know if you checked for vacuum leaks. Also, I need to confirm if this is the 3.5L or the 3.9L V6.
Let me know.
Joe
By chance, have you had a chance to check for vacuum leaks? Also, have you ever serviced the throttle body?
Here is a link that explains in general how it is done. Try this as well.
https://www.2carpros.com/articles/throttle-actuator-service
Let me know if you checked for vacuum leaks. Also, I need to confirm if this is the 3.5L or the 3.9L V6.
Let me know.
Joe
Apr 4, 2022 at 6:27 PM
3.5, I checked the vacuum best I know how never did it before. I had throttle body cleaned out. And I had plugs changed and they said that the plugs were running lean.
Apr 5, 2022 at 8:27 AM
Hi,
If it is running lean, either it is a vacuum leak issue or low fuel pressure. If you found no leaks, the next thing to check is fuel pressure to make sure it isn't low.
Here is a link that explains in general how it's done:
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
I attached the manufacturer's fuel pressure specifications below.
Let me know what you find.
Joe
If it is running lean, either it is a vacuum leak issue or low fuel pressure. If you found no leaks, the next thing to check is fuel pressure to make sure it isn't low.
Here is a link that explains in general how it's done:
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
I attached the manufacturer's fuel pressure specifications below.
Let me know what you find.
Joe
Images (Click to enlarge)
Apr 5, 2022 at 5:49 PM