1989 GMC Sierra Engine Missfire

1989 GMC SIERRA
10,100 MILES • V8 • 2WD • AUTOMATIC
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KWRIGHT57
  • MEMBER
  • 1 POST
This truck begins to missfire after it warms up. I changed the fuel filter and that hasn't solved the problem. Is it possible that the coil is bad and begins not functioning after it gets hot?
Dec 28, 2008 at 5:41 AM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
With a fuel injected vehicle, a fuel pressure gage is just like a screwdriver, you got to have one. Even if the issue isn't related to fuel pressure. You need to be able to rule something out.

Are there any codes? How long since the last tune-up? If the problem is temp related, you might think about the CTS coolant temp sensor. I'm not saying the sensor is faulty, I'm just throwing out possibilities.

If you think spark at the plugs is an issue, then check for spark at the plugs.
Dec 28, 2008 at 6:24 AM
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SHOULDABOUGHTACHEVY
  • MEMBER
  • 12 POSTS
If it's been a while since the last tune-up, you wouldn't be hurting anything to show the truck some TLC. Plugs, wires, cap and rotor, OF, FF, AF. At least.

Not saying it will fix anything, but if it's been a while, I bet it will make a huge difference.

Also, in my experience (that's not saying much, but I have ONLY ever owned 88-97 Chevys/GMCs) When a coil goes bad, it doesn't screw with you, it just goes bad.
Dec 28, 2008 at 6:05 PM
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