Car idles rough sometimes
Thread Starter
Racer
Joined: Jun 2009
Posts: 267
Likes: 2
From: Austin TX
Car idles rough sometimes
I have a 2007 with about 45k miles. Lately it has started to idle a little rough at stop lights at seemingly random times.
It does not idle rough consistently. Most of the time it will idle just great and even when it idles roughly, the RPMs of the motor do not sag. When it does start to idle rough, I do get a faint smell of gas and things get a little shaky.
When I catch it idling roughly, I will give it gas and when I start moving everything seems to be fine...then I get to the next light and it is idling correctly again.
I can't reproduce the problem. Sometimes it will do it after a cold start and other times it won't. It seems like it happens more when the motor is at a normal operating temperature.
I have tried some fuel additives and they seemed to have no effect. I checked the air intake to make sure the air filter was not clogged and all the connections were tight. I did not check the throttle body though.
I do have an aftermarket exhaust/intake, but I have had those on for over a year with no issues. I am thinking it may be a fouled spark plug, but I am not sure.
I am looking for any suggestions or if anyone else has had a similar problem. Thanks!
It does not idle rough consistently. Most of the time it will idle just great and even when it idles roughly, the RPMs of the motor do not sag. When it does start to idle rough, I do get a faint smell of gas and things get a little shaky.
When I catch it idling roughly, I will give it gas and when I start moving everything seems to be fine...then I get to the next light and it is idling correctly again.
I can't reproduce the problem. Sometimes it will do it after a cold start and other times it won't. It seems like it happens more when the motor is at a normal operating temperature.
I have tried some fuel additives and they seemed to have no effect. I checked the air intake to make sure the air filter was not clogged and all the connections were tight. I did not check the throttle body though.
I do have an aftermarket exhaust/intake, but I have had those on for over a year with no issues. I am thinking it may be a fouled spark plug, but I am not sure.
I am looking for any suggestions or if anyone else has had a similar problem. Thanks!
Safety Car
Joined: May 2011
Posts: 3,582
Likes: 46
From: va
you mentioned gasoline smell
This leads me to believe it cold just be an O2 sensor going bad
Id start looking there
If you can hook up a computer and drive around, for a while and log whats going on, Im sure youll be able to narrow it down. This sounds more like an electronics based issue...
good luck
This leads me to believe it cold just be an O2 sensor going bad
Id start looking there
If you can hook up a computer and drive around, for a while and log whats going on, Im sure youll be able to narrow it down. This sounds more like an electronics based issue...
good luck
Supporting Vendor
Joined: Mar 2002
Posts: 13,099
Likes: 672
From: Bristol, Tennessee
St. Jude Donor '09
There is a known issue with the LS3 and idle quality. The MAF sensors from different vendors appear to have low frequency, low idle issues. We have tested several stock LS3s and they all had long term fuel trim average variances from +5% to -9% within a two minute range.
Vararam has been seeing this issue for some time on their Camaro intake and ran down the problem to suspected bad MAF sensors. Here is their article. A good one. Notice the very last line in the test regarding the C6 LS3: http://www.vararam.com/camaro.html
Unfortunately, the intake gets the blame since it exacerbates an already weak meter at low rpm and Hz range.
Take it into the dealer if you get any codes, but if not, it is just a minor deal. You could try a newer MAF sensor and see if that squares away the minor blip.
Fuel smell is not good; have that checked immediately.
Jim Hall
Vararam has been seeing this issue for some time on their Camaro intake and ran down the problem to suspected bad MAF sensors. Here is their article. A good one. Notice the very last line in the test regarding the C6 LS3: http://www.vararam.com/camaro.html
Unfortunately, the intake gets the blame since it exacerbates an already weak meter at low rpm and Hz range.
Take it into the dealer if you get any codes, but if not, it is just a minor deal. You could try a newer MAF sensor and see if that squares away the minor blip.
Fuel smell is not good; have that checked immediately.
Jim Hall
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"World Class Performance for your Corvette"
Intake Design and Engineering since 1999
Halltech Systems, LLC
423-915-6056
For service email:
orders@halltechsystems.com
www.halltechsystems.com
Supporting Vendor
Joined: Mar 2002
Posts: 13,099
Likes: 672
From: Bristol, Tennessee
St. Jude Donor '09
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