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Old 10-25-2008, 10:22 AM   #1
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spark knock

Hello, i have a 2005 wrangler sport with 38k miles. When i bought it it was just 18k. I always have a spark knock at high speeds epsecialy when the car is hot. I might have a light knock at lower speed too but i don't hear it. Do you have any suggestions...thanks

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Old 10-25-2008, 12:09 PM   #2
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Are you certain you have the right spark plugs installed? Do you know what kind of plugs are installed?

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Old 10-28-2008, 01:42 PM   #3
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I did...i installed the ngk-r with 35 gap. Do you think that it might be the gas that i am using. I am using always 87 oct.
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Old 10-28-2008, 01:49 PM   #4
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87 octane is fine, it will not cause knock in an otherwise healthy engine. How do you drive your engine? Extremely conservatively? Very conservatively? Or do you regularly "get on it" with occasional hard acceleration up into high rpms?
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Old 10-28-2008, 09:24 PM   #5
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what mods have you done to the engine??? I would pull the NGKs and throw in some Champion copper truck plugs. When you pull the old plugs out check them to see which cylinder is giving you issuse. Also look into seafoaming the motor. Mopar engines like to get carbon build up, seafoam will clean it off. and yes carbon is what can cause spark knock
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Old 10-28-2008, 09:46 PM   #6
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yes carbon is what can cause spark knock
That's exactly why I asked him how he drove his TJ. Hard enough to keep the carbon out or so conservatively that carbon build-up inside the combustion chambers was likely.
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Old 10-29-2008, 07:39 AM   #7
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Maybe you're just getting crap gas. I notice a big difference if I fill up with Sunoco vs. Exxon. Exxon gas pings (no matter how I drive) and the Sunoco gas never does...both 87 grade...just my .02

IMO - before you pull the plugs, fill up at another supplier and re-evaluate.
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Old 10-30-2008, 08:45 AM   #8
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thanks for the tips guys...i do drive the car a lot every day...i make 80 to 90 miles everyday and the most of them in traffic....i will try to change the plugs again with the champion ones and i will try also a different gas...you are really very helpful...i just don't want to screw up anything on the engine...it's an amazing truck.
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Old 10-30-2008, 10:58 AM   #9
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Champions are fine but why not go with a platinum plug so you won't have to change them again so soon? If you went with something like an Autolite APP985 which is a double-tipped platinum plug (double-tipped means the platinum is on both sides of the gap), they'll easily last 90-100K miles and perform as well as the Champions will that entire 90-100K miles.

Just be careful if you go with platinums that you get the kind with platinum on BOTH sides of the gap like the APP985 (note the two P's in that part number) are that I recommended. Your newer style distributorless ignition system is fussy about the plugs it gets and it would not do well if you accidentally installed platinum plugs that only had the platinum on one side (called single-tipped) of the gap.

You never replied back on if you drive your engine very conservatively or hard though. Your engine might be carboned up if you drive it uber-conservatively which will cause knock/ping/pre-detonation. If it's carboned up, there are easy cheap ways to get rid of it.
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Old 10-30-2008, 11:39 AM   #10
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If it's carboned up, there are easy cheap ways to get rid of it.
I don't mean to steal this fellows thread, but can you go into any detail about how to get rid of the carbon in the engine? I've just purchased my Jeep back in August and I'd like to do it to mine. I've ran a can of Seafoam and Berrymans Chemtool through a couple of tanks of gas, but should I also inject it through the brake booster line to clean up the combustion chambers and tops of the pistons better?
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Old 10-30-2008, 11:52 AM   #11
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Here are a couple posts I wrote earlier on how to do this ky-homelite...

Jeep Wrangler Forum - View Single Post - seafoam and Jeep Wrangler Forum - View Single Post - jeep likes to turn it self back on after I walk away?

Both describe a very good method that is totally free that has been in use for probably 75 years that most mechanics are very familiar with.
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Old 10-30-2008, 02:05 PM   #12
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Here are a couple posts I wrote earlier on how to do this ky-homelite...

Jeep Wrangler Forum - View Single Post - seafoam and Jeep Wrangler Forum - View Single Post - jeep likes to turn it self back on after I walk away?

Both describe a very good method that is totally free that has been in use for probably 75 years that most mechanics are very familiar with.
Thank you, that is great information!

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