97 mustang gt an I put a 75mm throttle body a bigger throttle body housing an now my is running like crap


New Member
Mar 10, 2019
loretto tn
I put a 75mm throttle body an bigger housing with a cold air intake on my 97gt an now it is running like crap burning rich sounds like it is missing no power on the low end someone tell me do I need bigger injectors or bigger maf sensor an tuned
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Admin Dude
Jan 4, 1985
Box behind Walmart
I put a 75mm throttle body an bigger housing with a cold air intake on my 97gt an now it is running like crap burning rich sounds like it is missing no power on the low end someone tell me do I need bigger injectors or bigger maf sensor an tuned
You need to put the stock pieces back on.

Then, you should ask a lot of questions about why throwing this 75mm throttle body onto an otherwise stock induction system, is a really bad idea.


SN Certified Technician
Aug 14, 2009
Houston Texas
+1 on above. Likely the modifications have modified the readings of the MAF sensor where now the PCM "thinks" there is more air entering the motor than there actually is. Examples of "possible" causes:
  • there's a vacuum leak.
  • there's a wiring fault at the MAF that wasn't there before.
  • The MAF sensor itself has been damaged.
  • The modifications have changed the "index" of the MAF sensor where the MAF no longer reads correctly.
Want more proof? Here's some information on an affordable ODB2 scanner with advanced graphing capabilities. Start by looking at:
  • MAF flow.
  • Long term fuel trims (LTFT) at idle and 2000 RPM's.
Compare the reported values to the "normal" values for your motor. Look for changes in the LTFT's between idle and load. This will indicate a vacuum leak.

ForScan ODB2 scanner w ELM327 USB

Double check that the fuel rail pressure regulator intake vacuum reference line is connected and leak free. Double check all of your work. Even a tiny vacuum leak can cause huge problems.
Mar 21, 2019
Long Island
I have a 75 mm on mine. Shouldn't cause that. Sounds like the car is running lean and the car is overcorrecting and adding fuel over what it should. A bigger throttle body won't do anything to running condition except make the throttle less sensitive and become WOT more quickly. The real issue is a vacuum leak somewhere. From my understanding you have the stock MAF section or at least closely designed to stock which is all the engine management cares about. Honestly it sounds like a vacuum leak or similar. Unless you changed the MAF housing itself to something a good 1/4" bigger in diameter it's an assembly error not the parts.
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