Rough idle after warmed up

2008 FORD F-150
65,000 MILES • 5.4L • V8 • 2WD • AUTOMATIC
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ALEXF1502020
  • MEMBER
  • 1 POST
Hi,
Truck idles rough after warmed up and when the street is not level, the rough idle is worse. If I stop and put in transmission in park the rough idle goes away instantly.

Thanks,
Alex
Nov 11, 2020 at 2:15 AM
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KASEKENNY
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 18,907 POSTS
This could be a number of things. So let's start from the beginning and cross things off the list until we find something that doesn't add up.

To start we need to check for codes. Most parts stores still check codes for free if you don't have a code reader.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes then we need to check the fuel pressure and make sure it is correct.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Lastly, the most likely cause is a vacuum leak. So here is a guide that will help find a leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let's go through all this and see what turns up but my money would be on a vacuum leak so if you want to start with that after checking for codes then that is fine. Let us know what you find.. Thanks
Nov 11, 2020 at 5:39 AM
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