Truck struggles to go past 3,000 RPM's and intermittent not shifting

Tiny
DCANNON1390
  • MEMBER
  • 2002 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 115,751 MILES
I just replaced the spark plugs when I got a misfire code on my truck but now that I replaced them it struggles to go past 3,000 rpm's and doesn't want to shift sometimes. I wired up all the ignition coils correctly and did everything right. Does anyone know what it might be or what might be wrong?
Tuesday, August 25th, 2020 AT 1:53 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

Did this problem just start since the plugs were replaced? If it got worse since you replaced them, see if there is a new code that indicates which cylinders are causing the issue. Also, make sure the grounds weren't damaged for the ignition coils. See pic 1 for locations. Check to see if the connector at the ground point isn't loose or damaged. I've seen many of them break. If one does, you will have 4 of the cylinders working.

Let me know. Also, reconfirm that all connectors are tight and properly attached at the coils. Anything is possible.

Let me know what you find or if you have other questions.

Take care,
Joe
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Tuesday, August 25th, 2020 AT 7:28 PM
Tiny
DCANNON1390
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  • 40 POSTS
Yea, I will let you know. It's in limp mode rn I'll check in the morning.
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Tuesday, August 25th, 2020 AT 7:57 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

Let me know what you find. Rescan and check the grounds I mentioned.

I look forward to hearing from you. Don't worry. We'll get it taken care of.

Joe
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Tuesday, August 25th, 2020 AT 8:01 PM
Tiny
DCANNON1390
  • MEMBER
  • 40 POSTS
I checked the grounds they are good. So what could it be?
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Wednesday, August 26th, 2020 AT 6:19 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
If the coils are all good and working properly and there is no issue with the grounds, we need to scan the computer to see what new codes are set. Make sure by accident nothing was left disconnected as far as sensors and or vacuum components.

If you have a scanner, let me know what codes are present.

Joe
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Wednesday, August 26th, 2020 AT 2:31 PM
Tiny
DCANNON1390
  • MEMBER
  • 40 POSTS
Well, sadly it ended up in a broken head gasket.
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Monday, August 31st, 2020 AT 1:36 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

I'm sorry to hear that. Regardless, have you gotten it fixed?

Joe
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Tuesday, September 1st, 2020 AT 6:08 PM

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