Random misfire

Tiny
JOHNNIECOBB
  • MEMBER
  • 2000 CHEVROLET CHEVETTE
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 85,000 MILES
Changed the coil packs and wires a few months ago. Within the last month and a half I had a problem with my engine "jumping". Since it has been progressively worse so I stopped driving it for a while. Last week I drove it to work just to see what was going on, it started misfiring so I stopped and got out and popped the hood. It was dark out that night, on coil pack one I could see a small arc jumping from the coil pack to the rail that holds the coil packs in place, also the plug wire was burnt on the side that connects to the coil pack, the spark plug side was clean though. Today I drove it to work because I planned on replacing the coil pack and the wires, which I did. That did not solve the problem now it seems worse. On a side note the coil pack I replaced was melted some, all the other coil packs seem fine I checked though and all the wires. From here I checked my plugs to make sure they were not over gaped, which they are not. I am worried I have caused a bigger issue by driving.
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Thursday, October 13th, 2016 AT 11:23 AM

6 Replies

Tiny
JOHNNIECOBB
  • MEMBER
I will check the compression of this cylinder in about three hours. I am not sure what else to check for. It has not ran this bad before today. I am worried I caused a bigger issue by driving the car to work today. Before I changed the burnt coil pack I noticed it had black plastic coming out of it like it melted.
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Thursday, October 13th, 2016 AT 11:38 AM
Tiny
HMAC300
  • EXPERT
From your description sounds like it may be getting to much voltage have a mechanic scan for codes and freeze frame so he can read sensors. these are terrible to figure out and can take a ton of by a diy to fix as well as aggravation. this is one of the few things we send to a mechanic. As the problem can be any sensor/injector/ low fuel pressure or other things. if you like to check fuel pressure you can do that auto parts rent gauge as that can cause it as well. see link for that.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Thursday, October 13th, 2016 AT 12:21 PM
Tiny
JOHNNIECOBB
  • MEMBER
I did scan for a code, the code pulled was p0300 which is a random misfire code from my understanding. These are the causes of this code.
-Faulty Spark plug
-Faulty ignition coil
-Clogged or faulty fuel injector
-intake air leak
-Fuel Injector Harness is open or shorted
-Fuel Injection circuit poor electrical connection
-insufficient cylinders compression
-incorrect fuel pressure
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Thursday, October 13th, 2016 AT 1:12 PM
Tiny
HMAC300
  • EXPERT
Yes but a mechanic can go further with it. Check duct work for air leaks leading to engine an injector problem like a bad one check for ohms. And I would replace the coil that is melted.I already sent something on fuel pressure.
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Thursday, October 13th, 2016 AT 3:43 PM
Tiny
JOHNNIECOBB
  • MEMBER
I figured out what the problem was. Apparently I have a short in my wiring harness that is causing the entire left side of my engine to have no spark. Does anyone know the best way to trouble shoot my harness? I have narrowed it down that the short is happening before it reaches my coil packs.
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Friday, October 14th, 2016 AT 8:38 AM
Tiny
HMAC300
  • EXPERT
Use an ohm meter to go to pins on PCM if more than five ohms then it is too much or if it is shorting out you can sometimes take compass and run it along the harness with engine running and it will go crazy when you hit the short. Check harness to see if it is grounding out. If you wiggle the harness and misfire stops then check harness at that point for grounding out.
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Friday, October 14th, 2016 AT 9:27 AM

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