Intermittent misfire.

cbxer55

Active Member

Jan 25, 2020

318

69

38

Oklahoma

May 15, 2021

#1

• May 15, 2021

• #1

4.0 V-6. I don't get it. How can a misfire be intermittent. Most of the time, I start it and it runs great. Every once in a while, most especially after a hot start, it develops a misfire. That it's intermittent means it's not likely the usual culprit of plugs, coils or wires. Has to be something amiss in the computer electronics. Drove it to work yesterday, it was fine. Drove it at lunch four hours later, it was fine. Drove it home two hours later, missing bad. Could tell just giving it some gas. Started it up a while ago, it's fine.

Any ideas?

 

HemiRick

I'd be looking at jacking under the house

Jun 28, 2020

723

272

73

Memphis TN

May 15, 2021

#2

• May 15, 2021

• #2

it certainly could be plugs, wires or coils.....pull the codes and swap parts.

 

cbxer55

Active Member

Jan 25, 2020

318

69

38

Oklahoma

May 16, 2021

#3

• May 16, 2021

• #3

Coils, plugs and wires were replaced in May last year. I pulled the plugs today, they all look identical. Code is P0300, Random Misfire.

 

cbxer55

Active Member

Jan 25, 2020

318

69

38

Oklahoma

May 21, 2021

#4

• May 21, 2021

• #4

I think what may have happened is that when I put the new wires on back when, I didn't put one or two of the wires on the plugs tight enough. When I pulled them off to check them, two came off without making that snapping sound. Made sure when I reinstalled them, that I felt that click, that indicates fully engaged. Problem gone. I guess they were close enough to cause an arc, but yet still not cause an arc occasionally?

 

7991LXnSHO

wanna catch the space herp

10 Year Member

Sep 1, 2010

7,387

2,745

194

Kearney, NE

May 21, 2021

#5

• May 21, 2021

• #5

cbxer55 said:

I think what may have happened is that when I put the new wires on back when, I didn't put one or two of the wires on the plugs tight enough. When I pulled them off to check them, two came off without making that snapping sound. Made sure when I reinstalled them, that I felt that click, that indicates fully engaged. Problem gone. I guess they were close enough to cause an arc, but yet still not cause an arc occasionally?

Click to expand...

A bad connection somewhere making intermittent contact was one of my top two predictions, followed by impending component death. This fits it as well as anything. I hope you used dielectric grease so the boots are sealed from water a bit and come apart without destruction next time.

 

Reactions: cbxer55

cbxer55

Active Member

Jan 25, 2020

318

69

38

Oklahoma

May 21, 2021

#6

• May 21, 2021

• #6

7991LXnSHO said:

A bad connection somewhere making intermittent contact was one of my top two predictions, followed by impending component death. This fits it as well as anything. I hope you used dielectric grease so the boots are sealed from water a bit and come apart without destruction next time.

Click to expand...

ALWAYS! There was no destruction. I put the same wires and plugs back on it. Plugs looked fine. Wires and coils were new last May.