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Discussion Starter · #1 ·
My poor little 4 banger is getting bad mileage and has a terrible spark knock. Replaced plugs and wires, made sure they were gapped right, no help.... any one else had this problem, or have any ideas? I aslo have used fuel injector cleaner, seems to help for a little bit, not much though.....
 

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Discussion Starter · #3 ·
SPARK KNOCK

Definition: This is the pinging or rattling noise sometimes heard during acceleration that indicates detonation is occurring inside the engine
 

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Discussion Starter · #4 ·
this is a better definition:
Spark knock is when the spark of the spark plug ignites the fuel/air charge in the combustion chamber sooner then it should.

mine only occurs during acceleration.....
 

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somehow the distributor cap is off causing it to happen? Maybe bad tank of gas? (lower octane rating the more likely to get knock)
 

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^^^ yah - replace the cap and rotor as well. If the rotor is a little sloppy that might be causing it. Bout how many miles are on the motor? I doubt it would be the distributor giving the slack.... but check and see if your timing has jumped.
 

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On my 95 I switched a couple wires when I did a tune up. Ran similar to what you are saying. Make sure you have the firing order right.
 

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Drives by Braille
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coil may be going bad too. had a bad coil in mine and gave me all sorts of problems.
usually when a coil goes, its gone. The tollerances that they need are pretty tight and if they fall below on either side it won't even start the car... but I would suggest a nice MSD blaster coil. For the money, is a great upgrade!
 

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I was curious about this, so I did some research. From what
I've found, it is a serious issue that has to do with a problem with the ECU. MSD may be a good solution though...
 

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Discussion Starter · #11 ·
its got 66 thousand on it..... thanks for all the info guys, rely appreciated, I'll keep everyone updated, little crazy round here with the holidays and all.....
 

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Discussion Starter · #12 ·
I was curious about this, so I did some research. From what
I've found, it is a serious issue that has to do with a problem with the ECU. MSD may be a good solution though...
What kind of a problem and how serious? Cap and rotor are new, nothing is loose or anything, wires are all in the right place, so should I try replacing the coil and go from there? Any advice would be helpful..... money's tight till after Xmas, so I don't want to go buying parts hoping they work..... Thanks a bunch guys!
 

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From what I have read, it seems to be very serious. I don't want to scare you. Keep in mind, it's just internet banter I have seen on it. The info I saw pointed toward a computer issue and the solution was not cheap.

If it were mine, I'd probably have to break down and get a pro to check it out.
 

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From my experience, what it sounds like is either spark or fuel. It seems you've worked on the spark, so I would assume it's the fuel. Either your fuel injection is not operating properly, or your computer is not giving the proper information to the operating systems. Can't get more specific than that.

I also recommend a professional, even though I hate to do that unless you have someone that you can trust. It could be something simple like an injection cleaning, but most garages are in the business of making money and like to add on extra work that can't hurt, but one may not need.
 

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I don't believe fuel is the issue. The spark timing being off is what causes spark knock. I've done a lot of reading, since a few days ago, I had never heard of it.

The spark timing being off usually affects only one plug, so adjusting the time is useless.
 

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how long has it been doing this? on my old truck, 1 bad tank of gas would make it ping like the devil for that entire tank, plus 2 more tanks of premium.

does the engine seem to be running any hotter?

do the newer jeeps have an EGR system? a stuck EGR valve would make it run lean and ping.

if its only been a short period....fill up with premium gasd and run a bottle of chevron techron.

pull your plugs....see what they look like. if one is whiter than the others, its leaning out on that cylinder and that one is your problem. if they ALL look white, theyre ALL leaning out.

dont take it to the stealer just yet....
 

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Oh, I didn't notice, was the distributer replaced ?

This is only my opinion based on my own past problem with another vehicle, but I had a computer problem that caused the same kind of knock (that a spark timing problem would cause). The mechanic told me the computer was telling the injector to send the fuel a "half beat" off. He may have been making up a story, I'm not knowledgeable enough about auto-computers to know better. It ran normal (without the knocking) after the computer was replaced ($300). This was not on a Jeep though.
 

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That sounds right. I hadn't thought of the fuel being sen through the injector in poor timing, but rather the spark being sent in poor timing. I guess it could go either way.
 

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if he can identify which cylinder is pinging, he can swap injectors to identify if its the injector itself or the computer deal y'all are talking about....
 
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