Engine misfiring?

Tiny
LUTTRELLDAVID21
  • MEMBER
  • 2003 FORD MUSTANG
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 154,000 MILES
So I replaced the alternator on my car and when I put the serpentine belt back on the belt tensioner was bad, so I replaced the tensioner and the serpentine belt because it broke it at the same time. Since I started my car, it runs like half the cylinders. It seems If I hold it on the floor it might get up to 2,200 RPMs.
Wednesday, May 21st, 2025 AT 2:35 PM

6 Replies

Tiny
STEVE W.
  • MECHANIC
  • 14,493 POSTS
As the belt broke, I would look at the crankshaft sensor to see if it was damaged by the belt. It is located near the balancer on the front of the engine. Also look at the other wiring in the area and look for any damage.
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Wednesday, May 21st, 2025 AT 7:37 PM
Tiny
LUTTRELLDAVID21
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Could this have made it jump time? Because that's what it acts like.
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Wednesday, May 21st, 2025 AT 8:47 PM
Tiny
LUTTRELLDAVID21
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Could this have made it jump time? Cause that's what it acts like
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Wednesday, May 21st, 2025 AT 8:47 PM
Tiny
STEVE W.
  • MECHANIC
  • 14,493 POSTS
That is a keyed system, so it is possible that it grabbed and cracked it and sheared the key in the process. That is an easily replaceable part at least. I would get a replacement balancer, front seal and key. Then it's a matter of removing the belt, unbolt the balancer and use a puller to remove it. Replace the sheared key and install the replacement part. Torque it to 118 lbft and reinstall the belt.
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+1
Thursday, May 22nd, 2025 AT 1:15 AM
Tiny
LUTTRELLDAVID21
  • MEMBER
  • 4 POSTS
That actually sounds right. Thank you so much for the answer. I'll let you know what the results are.
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Friday, May 23rd, 2025 AT 8:16 AM
Tiny
STEVE W.
  • MECHANIC
  • 14,493 POSTS
Let us know what you find.
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Friday, May 23rd, 2025 AT 5:22 PM

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