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can vacuum leak and/or bad o2 sensor cause idle problems?

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Old 07-08-2014, 01:35 PM   #1
robotnix
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Default can vacuum leak and/or bad o2 sensor cause idle problems?

hi,
so a vacuum leak or a bad o2 sensor or both...
can this cause idle issues.

my mustang sometimes does that when it's hot

I have code 91 which means bad o2 sensor on driver side. I'll change it next year when I change, header, xpipe and cat.

but can a bad o2 sensor screw up idle sometimes? it never happens initially but it happens when motor is hot.

thanks.
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Old 07-08-2014, 02:37 PM   #2
dawson1112
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Yes and Yes, vacuum leaks and or bad o2 sensor can cause poor idle.

o2 sensor more so when engine reaches operating temperature and the ecm goes into closed loop. The o2 sensors don't come on line until they heat up a bit.
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Old 07-08-2014, 03:06 PM   #3
bluebeastsrt
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Quote:
Originally Posted by robotnix View Post
hi,
so a vacuum leak or a bad o2 sensor or both...
can this cause idle issues.

my mustang sometimes does that when it's hot

I have code 91 which means bad o2 sensor on driver side. I'll change it next year when I change, header, xpipe and cat.

but can a bad o2 sensor screw up idle sometimes? it never happens initially but it happens when motor is hot.

thanks.
Why wait? the o2 is a cheap and easy job. Get a can a carb cleaner and spray around intake, throttle body etc to find any leaks.
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Old 07-08-2014, 04:16 PM   #4
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Quote:
Originally Posted by bluebeastsrt View Post
Why wait? the o2 is a cheap and easy job. Get a can a carb cleaner and spray around intake, throttle body etc to find any leaks.
I'm waiting because the bad o2 sensor has become one with the header so I have to change the header too. a friend tried heating up the o2 sensor but nothing to be done only way is to cut the header pipe so I might as well just wait since I want to replace the entire exhaust system.


for the vacuum I was thinking of using the fog or smoke machine I got from ebay.

thank you for the information.
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