2003 Mustang GT bogging down

OscarRamirezJr

New Member
Feb 3, 2019
1
0
0
34
McAllen Texas
Mustang gt bogs out at 50mph. I know it’s pretty vague, but anybody have any clue as to what could be causing this? It has aftermarket Borla exhaust so I’m thinking maybe some kind of o2 sensor got messed up. Car runs fine. Tranny was checked and all is good there. It’ll shift all gears but when I shift to 5th gear on the highway it bogs down and won’t go any faster
 
  • Sponsors(?)


PonyRyder

Member
Jan 17, 2019
7
1
13
62
Arizona
When was the last time the plugs were replaced? I'd consider the PCV valve as well or possibly a vacuum leak that shows up at higher speeds.
 

Onesick99GT

Active Member
Nov 20, 2018
359
47
38
33
Dayton, Ohio
How does it run when under high load? Burning tires, dropping the clutch ect. A failed oxygen sensor would cause several issues. Your mpg would suffer dramatically since the pcm would have no idea as to what your airflow ratio is. Signs would be a strong odor of fuel. The pcm makes corrections based on your oxygen sensor. When in 5th gear hitting the gas and it doesn't go would lead me to believe its getting too much fuel or not enough causing the issues. Have you check your codes? How many miles are no the car? Has the oxygen sensors been replaced before?
 

jeremy1275

New Member
Oct 1, 2019
1
0
1
44
Florida
Hi. New here. I have same problem. I have 2 codes. EGR , cuz it was deleted, and O2 sensors saying rich. However O2 sensors are good. I checked OHMS . I have an 03 GT roush clone. I bought it that way. Roots style/Eaton supercharger. 40lb injectors,CAI,New MAF. Fuel pump, 4.10 gears. It ran great after I got it. She was screaming. It had a vacuum leak that caused initial problem. I smoked engine and found initial leak. Still does this. Cold it's fine. Warm and when I try to floor it bogs down and will backfire. I let off a little and goes ok. I'm tired of trying to figure out. I should be blowing away other cars, but damn thing bogs when trying to floor it. It sucks cuz I want to hear my supercharger whine and I only get the satisfaction when it's cold.