1998 Mustang GT won’t stay running.

Blue2v

New Member
Sep 27, 2019
3
0
1
20
DeFuniak Springs, Florida
I have a 1998 Ford Mustang GT with a 2005 Crown Vic engine. The car was running flawless when I parked it one night. The next morning I went too start it and it barely starts up. Battery and alternator are good. Once it starts running it runs really rough and will shut off if I touch the throttle at all. It’s almost like it is losing vacuum. Is there any specific places I should be looking for leaks or what is the easiest way to find the leak?
 
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Potomus Pete

Is there a trick , or does my wife just hold it
Mar 7, 2019
1,057
345
93
56
Sarasota Florida
I have a 1998 Ford Mustang GT with a 2005 Crown Vic engine. The car was running flawless when I parked it one night. The next morning I went too start it and it barely starts up. Battery and alternator are good. Once it starts running it runs really rough and will shut off if I touch the throttle at all. It’s almost like it is losing vacuum. Is there any specific places I should be looking for leaks or what is the easiest way to find the leak?
If its so bad the car wont run you should be able to hear it begging for air. I dont think its vacuum . Do the No Start Checklist . Check fuel pressure. Tell us what it was....
 

wmburns

SN Certified Technician
Aug 14, 2009
5,838
505
194
Houston Texas
+1 on above. Look for a vacuum leak.

It would be handy to know:
  • what the fuel pressure is
  • What the MAF flow is. Does the MAF flow change during cranking or when the throttle is advanced? Does it make any difference IF the MAF is disconnected?
  • What is the PCM operating mode (open or closed loop)?
  • What is the battery voltage?
ForScan ODB2 scanner w ELM327 USB
 

Jimmy5

New Member
Feb 15, 2020
13
2
1
65
Salem, Oregon
I have a 1998 Ford Mustang GT with a 2005 Crown Vic engine. The car was running flawless when I parked it one night. The next morning I went too start it and it barely starts up. Battery and alternator are good. Once it starts running it runs really rough and will shut off if I touch the throttle at all. It’s almost like it is losing vacuum. Is there any specific places I should be looking for leaks or what is the easiest way to find the leak?
I would try replacing the Throttle body air inlet motor. Probably stuck, if there is any load on motor, even shifting into gear and dies, its the Air inlet motor. If You want You could replace the Throttle position sensor too (its cheap $15).
 
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