Backfiring and will not accelerate passed 25 MPH?

Tiny
YBJUAN
  • MEMBER
  • 1995 DODGE RAM
  • 5.9L
  • V8
  • 2WD
  • AUTOMATIC
  • 300,000 MILES
After replacing flex plate my truck would not start until I changed crankshaft position sensor and now its backfires in idle as well as accelerating and it won't go past 25 MPH.
Tuesday, December 26th, 2023 AT 1:11 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

Where did the new crankshaft position sensor come from? I have been seeing so many faulty aftermarket parts recently. Do you still have the original one that was removed? Was it faulty or just replaced because you were working on the trans? If it was replaced simply as preventative maintenance, reinstall the old one and see if the backfire goes away.

The backfiring is likely being caused by the new sensor. I would remove it and return/replace it to see if that makes a difference. Keep in mind, I am assuming the backfiring started after the new sensor was installed.

Take a look through this link, it explains how to repair common causes of an engine backfire:

https://www.2carpros.com/articles/engine-backfires-while-running

Let me know.

Take care,

joe
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Tuesday, December 26th, 2023 AT 9:51 PM
Tiny
YBJUAN
  • MEMBER
  • 15 POSTS
My truck wouldn't start, I was told to change the crankshaft position sensor and it started right up but then I noticed the backfiring. I got the part from Orielly.
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Wednesday, December 27th, 2023 AT 10:47 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

Either the new sensor is faulty or not fully installed. That is what determines the sequence and timing of spark to the plugs. If you are getting a backfire and it started after the sensor was installed, those two possibilities are my first suspects.

Since it just started doing this, recheck your work. Make sure the sensor is fully installed and tight. Also, check to make sure the electrical connector and wiring are both in good condition.

If there are and you find no issues, my suggestion is to remove the sensor, take it back to the parts store, and request a new one under warranty.

Please understand, I know that I could be wrong. Not being there with you makes it more difficult to diagnose. However, this seems to be the most logical sense.

Let me know.

Take care and if I don't hear from you, have a great New Year.

Joe
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Wednesday, December 27th, 2023 AT 9:13 PM

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