Changed Spark Plugs, now its running rough

B

Begester

Petty Officer 1st Class
Joined
Oct 23, 2006
Messages
203
I just got done changing the spark plugs on my 1968 Cadillac (which is a great deal easier than my boat), and now the engine is running rough. I changed only the plugs, which looked like the photo shown. The car ran fine before I changed the plugs, but its been awhile since I've done them so I thought it was time.

I was checking the connections of all the wires and got "jolted" by one of the cable connections. Is it possible that one of the connections is bad? Are there any other things that this could be? plugs.JPG

Any help is greatly appreciated.

Cheers.
 
Beefer

Beefer

Lieutenant Commander
Joined
Aug 4, 2008
Messages
1,737
Re: Changed Spark Plugs, now its running rough

Sounds like a bad plug wire. Was one of the wires stuck? You may have damaged the wire or the connector inside.

I like to change my wires at the same time as the plugs, unless they look fantastic.
 
jimr

jimr

Senior Chief Petty Officer
Joined
Mar 21, 2004
Messages
723
Re: Changed Spark Plugs, now its running rough

1st it probably needs wires.
2 I hope you didn't put platinum plugs in it they are not ment for such an old car.
3 does it have points being that old if so may be burned or need setting and dwell set.
 
Boomyal

Boomyal

Supreme Mariner
Joined
Aug 16, 2003
Messages
12,072
Re: Changed Spark Plugs, now its running rough

At minimum you need to replace the plugs with the recommended ones. Too many times I have seen some of these 'special' plugs cause running issues. Also, as mentioned, you could have plug wires arcing.
 
B

BlueLightSpecial

Petty Officer 2nd Class
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Dec 2, 2011
Messages
152
Re: Changed Spark Plugs, now its running rough

Get a plant sprayer, and spray the wires with water while the engine is running. You should see the fireworks and hear the arcing if the wires are bad. I personally never had luck reusing plug wires on older vehicles. Its good practice to change both at the same time.
 
N

no704

Petty Officer 2nd Class
Joined
Apr 22, 2009
Messages
199
Re: Changed Spark Plugs, now its running rough

^^^Got to agree with that, don't have to go to the wet, butt run it in the dark and look for arcing. caddy motor replace with AC or champions only!
 
B

BlkY2k

Chief Petty Officer
Joined
Aug 20, 2010
Messages
583
Re: Changed Spark Plugs, now its running rough

You may have cracked a insulator also. I second the sprayer idea, works good for figuring witch cyl is misfiring.
 
B

Begester

Petty Officer 1st Class
Joined
Oct 23, 2006
Messages
203
Re: Changed Spark Plugs, now its running rough

Thanks for all the replies. I pulled the plugs again and found that I had inadvertently bent one of the plug tips and and there was no gap for the spark.

Good to know about the correct use of plugs. I went back to the Delco's and it runs like a new one!

Cheers.
 
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