Misfire cylinder six

1998 GMC SONOMA
245,000 MILES • 4.3L • V6 • 4WD • AUTOMATIC
Avatar
RCA195203
  • MEMBER
  • 69 POSTS
I did a top end overhaul and now I have a misfire on number six according to my scanner. Plug wires, plugs, distributor is all new. I did a compression check and number 1/140, 2/130, 3/135, 4/130, 5/135, 6/125. You can see that the number six is the lowest. Will a hotter plug give me a better fire in the low compression cylinder?
Sep 21, 2018 at 3:19 AM
Avatar
DANNY L
  • ✓Experienced Mechanic
  • 5,648 POSTS
Hello, I am Danny.

You can give that a try but it probably will not help much to restore performance. Did you try doing a wet compression test? Add a little motor oil to that cylinder and retest. If compression goes up that tells you the piston rings in that cylinder are bad. Hope this helps and feel free to ask any questions. Thanks for using 2CarPros.
Danny-

https://www.2carpros.com/articles/the-reasons-for-low-compression
Sep 21, 2018 at 6:25 AM
Avatar
RCA195203
  • MEMBER
  • 69 POSTS
Yes I did Danny, and I figured that the rings were going out but hoped it was the head gasket but it was not! I might have an exhaust manifold leak though, would that cause a misfire code?
Sep 22, 2018 at 6:34 AM
🔧 Tools & Auto Repair Parts
Find automotive tools, diagnostic equipment, and replacement parts for your next repair.
Shop on Amazon →
Paid affiliate link. As an Amazon Associate, we earn from qualifying purchases.
Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Ask a new question

Frequently Asked Problems for This Vehicle