Sponsored

2017 Mustang GT Rough Idle / Car shutting off

S550Felipe

Member
Joined
Aug 4, 2020
Threads
6
Messages
19
Reaction score
4
Location
Los Angeles , CA
First Name
Felipe
Vehicle(s)
2017 Mustang GT
I recently got a ported 18 mani and 47lb Injectors installed on my car. I also installed a p51 intake. The car is tuned by lund. I have trouble codes p0300 and p0316. The problem I have is that my cars rpms randomly go up and down. Also if I rev the car a bit while in neutral it will rise up then completely go down and the car will shut off. Also if im driving in the street and go into neutral it will sometimes just die off. Ive also noticed that when I blip the throttle to rev match , the rpms kind of hesitate to go up. This was happening only on e85 but it now happens on 91 as well.
I have already changed the spark plugs and checked the coils.
Any help would be appreciated. Thanks!
I have a video of the car shutting off but idk if I can post that.
Sponsored

 

Cobra Jet

Well-Known Member
Joined
Feb 12, 2015
Threads
707
Messages
16,237
Reaction score
17,947
Location
NJ
Vehicle(s)
2018 EB Prem. w/PP and 94 Mustang Cobra
Check wires to connector and connection at crankshaft position sensor for the P0316.

The P0300 is just a random misfire code, the most common posted all over this site. If it were an actual cylinder issue, it would be a P0301-P0308 (with the end # designating the cylinder).

This thread may give some enlightenment to Ford's misfire strategies:
https://www.mustang6g.com/forums/threads/good-tech-article-on-ford’s-misfire-strategy.108076/

Also to note, this thread contains shop manual info about diagnosing the S550 misfires:
https://www.mustang6g.com/forums/threads/misfiring-even-after-replacing-coils.153240/#post-3124335

—-
If you have not already, you can try to do a crank relearn procedure:

Check the pdf in this linked thread; any time there is major engine work or trans work performed on the S550 5.0, the Dealer Service Tech (or DIYer) is supposed to do a crank relearn procedure.

https://www.mustang6g.com/forums/th...s-weird-hesitation.125119/page-2#post-2679084

Also check this link if you have a n-gauge for crank relearn:
https://www.mustang6g.com/forums/threads/new-clutch-dtc-and-shudders.148583/#post-3035678
 

mustangdriver

Active Member
Joined
Mar 21, 2021
Threads
1
Messages
31
Reaction score
42
Location
Illinois
First Name
Jim
Vehicle(s)
2015 Mustang
Your symptoms point to a vacuum leak, especially the hesitation on throttle blip.
A hesitation on throttle tip in is lean mixture.
 
OP
OP
S550Felipe

S550Felipe

Member
Joined
Aug 4, 2020
Threads
6
Messages
19
Reaction score
4
Location
Los Angeles , CA
First Name
Felipe
Vehicle(s)
2017 Mustang GT
Check wires to connector and connection at crankshaft position sensor for the P0316.

The P0300 is just a random misfire code, the most common posted all over this site. If it were an actual cylinder issue, it would be a P0301-P0308 (with the end # designating the cylinder).

This thread may give some enlightenment to Ford's misfire strategies:
https://www.mustang6g.com/forums/threads/good-tech-article-on-ford’s-misfire-strategy.108076/

Also to note, this thread contains shop manual info about diagnosing the S550 misfires:
https://www.mustang6g.com/forums/threads/misfiring-even-after-replacing-coils.153240/#post-3124335

—-
If you have not already, you can try to do a crank relearn procedure:

Check the pdf in this linked thread; any time there is major engine work or trans work performed on the S550 5.0, the Dealer Service Tech (or DIYer) is supposed to do a crank relearn procedure.

https://www.mustang6g.com/forums/th...s-weird-hesitation.125119/page-2#post-2679084

Also check this link if you have a n-gauge for crank relearn:
https://www.mustang6g.com/forums/threads/new-clutch-dtc-and-shudders.148583/#post-3035678
Thanks for the info!
 

Cobra Jet

Well-Known Member
Joined
Feb 12, 2015
Threads
707
Messages
16,237
Reaction score
17,947
Location
NJ
Vehicle(s)
2018 EB Prem. w/PP and 94 Mustang Cobra
What would be the best way to find a vacuum leak ?
With engine at idle, spray carb cleaner or EFI throttle body cleaner around intake mating surfaces, throttle body, air intake tract, and any rubber hoses going to the intake system. If there is a leak, you will hear the idle change as the carb cleaner is sucked through the source of the leak.
Sponsored

 
 




Top