# Which plug is bad? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [October 2, 2022, 2:49am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671 "2022-10-02T02:49:48Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 2, 2022, 2:49am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/1 "2022-10-02T02:49:48Z")
![image](https://global.discourse-cdn.com/cartalk/original/3X/7/1/71952829bb914e41c3ece48bdcc6fbec3de88e15.jpeg) I think the ground electrode is worn. Rear bank of course. My dbl platinum is single plat now ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [October 2, 2022, 2:51am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/2 "2022-10-02T02:51:08Z")
The right one. Tester ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 2, 2022, 2:59am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/3 "2022-10-02T02:59:47Z")
And the better one is pretty shaky too ![image](https://global.discourse-cdn.com/cartalk/original/3X/9/c/9ca7da34324734afc48cd35ee89ac4a63d41770a.jpeg) ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 2, 2022, 10:30pm UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/4 "2022-10-02T22:30:26Z")
I removed coil pack to reach rear plugs and swapped 2 wires and had rough idle. Always something. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 3, 2022, 12:24am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/5 "2022-10-03T00:24:14Z")
> [@Cavell](#): > > swapped 2 wires and had rough idle. Neighborhood kids would occasionally decide to play a prank on my dad, switch the plug wires around on his truck , engine starting up the next day … rrrrrr … kerplunk kerplunk kerplunk .. hiss.. .. lol … didn’t seem to phase him much. I guess he’d done that in his teenage years and knew the symptoms and how to fix it straight-away. Plug wires on my own truck are therefore numbered .. lol .. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 3, 2022, 3:00am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/6 "2022-10-03T03:00:09Z")
It has canted valve heads and I was using a mirror to check left/right angle to put plugs in as it is firewall side and I could see an edge of valve thru plug hole? I guess I never really spend much time looking down plug holes but I am pretty sure I’m not supposed to see valve. Then it started with rough idle and I found plug wire issue. Seems to idle fine now. Maybe all is well? ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [October 3, 2022, 3:03am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/7 "2022-10-03T03:03:52Z")
Nothing unusual about seeing a valve through a spark plug hole on a modern day engine. Now if you’re working on a Ford flathead… ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 3, 2022, 1:33pm UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/8 "2022-10-03T13:33:46Z")
![image](https://global.discourse-cdn.com/cartalk/original/3X/d/c/dc6bf599f4371c1fb741d293ee7dd69cb88242c2.jpeg) Valve does move at angle. ---
**Author:** ![wentwest](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/wentwest/32/6073_2.png) [@wentwest](https://community.cartalk.com/u/wentwest)\ **Post date:** [October 3, 2022, 3:54pm UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/9 "2022-10-03T15:54:42Z")
Seeing a valve is not a big deal. I hope you replaced those worn plugs while you were in there - that job is too much of a PITA to do it twice. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 3, 2022, 4:25pm UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/10 "2022-10-03T16:25:18Z")
Yes, new plugs. I unplugged all wires to get coil out and got them mixed up. 1 plug was very worn. Yes, the plug hole hole were I could see valve edge. The other plugs looked ok ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [October 25, 2022, 3:44pm UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/11 "2022-10-25T15:44:56Z")
I got another car. 180k miles. Seems to run ok. I pulled a plug and it has .070 gap. Electrode is about flush with porcelain. Spec is .035-.044 approx depending on brand of plugs. Were plugs changed at 100k? Or never? This is pic from pat goss’s garage. Looks like my plug. All 4 were identical. 15 min job. ![image](https://global.discourse-cdn.com/cartalk/original/3X/7/6/76386160564279100ef481af1339b05ae61d9dbd.jpeg) ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 26, 2022, 12:21am UTC](https://community.cartalk.com/t/which-plug-is-bad/186671/12 "2022-10-26T00:21:49Z")
Running engine with plug gap incorrect can stress the coils. Suggest to keep in mind if performance problem develops in future.