Recently my 1996 mustang gt has been hesitant under throttle (feels slow). If i give it throttle it sputters along and makes a humming sound especially when i go up a hill. What could this be? i read it could be the spark but i have new spark plugs and wires in the car. The coil pack been on the car ever since i got it. On start up my car idles very high around 1500 rpm and stays there until the car is warmed up or i put it in gear once it gets a nice idle going it jumps from 5500 rpm to 750 rpms at idle. i checked for vacuum leaks and found none not sure what else to check for. Could this be a bad coil pack? Any info would help
96 Mustang Gt Shudders Under Throttle Why?
- Thread starter Sn95bythebay
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wmburns
SN Certified Technician
Before we get started. Have you:
As far as if your problem "could be" a bad coil pack? Maybe. But the odds favor a bad coil pack would have misfires. Do you have any Misfires or misfire related DTC codes?
Does the humming sound go away if the IAC is disconnected?
Here's some more information on how to trouble shoot Idle/IAC issues.
http://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/
A sometimes over looked cause can be broken motor mounts. The Mustang is very hard on motor mounts. Every time I have worked on a Mustang with broken motor mounts, if you know what to look for the motor actually sets lower in the K-member.
- Cleaned the MAF?
- check the battery to confirm that it holds a charge?
- Checked the alternator for correct output or excessive AC ripple (bad diode)?
- Check the fuel pressure regulator intake vacuum reference line to be sure it's connected and leak free?
- Checked the spark plugs wells for signs of moisture?
As far as if your problem "could be" a bad coil pack? Maybe. But the odds favor a bad coil pack would have misfires. Do you have any Misfires or misfire related DTC codes?
Does the humming sound go away if the IAC is disconnected?
Here's some more information on how to trouble shoot Idle/IAC issues.
http://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/
A sometimes over looked cause can be broken motor mounts. The Mustang is very hard on motor mounts. Every time I have worked on a Mustang with broken motor mounts, if you know what to look for the motor actually sets lower in the K-member.
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wmburns
SN Certified Technician
The "things" inside the alternator that converts the Alternating Current (AC) to Direct Current (DC).
Diode bridge
https://en.wikipedia.org/wiki/Diode_bridge
https://en.wikipedia.org/wiki/Diode
trinity_gt
10 Year Member
The humming sound might be key: Take the tube connecting the MAF to the throttle body off and check it carefully for cracks. If it's cracked, you're getting unmetered air into the engine (i.e. a vacuum leak).
The humming sound may be air entering the intake through the crack.
The humming sound may be air entering the intake through the crack.
aftermarket cai and no cracks plus the car only makes that noise under load like going up a hill
Moosee1955
Active Member
- Sep 30, 2016
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What dtc codes do you have? Have you run a codes test. And yes check around air filter hose maf sensor. Do the basics, put a volt meter across battery 12.5 key off, 13.8 or higher running. Spray around all intake gaskets and hoses. Eliminate all vacuum leaks. Keep us posted
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wmburns
SN Certified Technician
The vacuum line running through the firewall is for the AC/heater damper motors. Normally the damper line is sized small enough that a vacuum leak won't cause huge problems. Further it's rare for the line itself to be the leak source. If this were my car I would be looking for a leak in the AC/heater control module.
For a test, it's possible to disconnect and plug the line to see if this resolves/improve the original symptom.
For a test, it's possible to disconnect and plug the line to see if this resolves/improve the original symptom.
