Automotive Spark Plug And Ignition Repair

Learn how to change spark plugs and replace ignition wires yourself with these automotive repair tips and instructions.

If your vehicle is running rough or the fuel mileage has dropped, it may need a new set of spark plug wires or plugs or both.

Check the owner's manual, or if you don't have one, check the internet for the manufacturer's recommendations on when to replace the plugs. Before purchasing plugs, pop the hood and check the condition of the ignition wires. If they're cracked, discolored or burned, put them on the replacement list also. Or if your engine just doesn't seem to be running smoothly, including at idle, the plug wires could be giving up the ghost.

A telltale check is to listen for clicking sounds with the hood open that could signify that the wires are shorting out the electrical charge before it gets to the plug. Pop the hood at night, and you'll see the sparks. Another way to check plug wires is-with the engine off--pulling each wire off its spark plug and again checking for discoloration, obvious burns, frayed or cracked insulation or obviously loose connections. We're talking high voltage here, so any touching is done with the engine off.

It's time for some warnings early in the game. Depending on the engine, you may not be able to see some of the spark plugs. A small mirror at the end of a metal rod available at your friendly local parts purveyor can help you see what's at the end of the wire and help you scope the best way to attack the objective.

Another warning is don't pull all the spark plug wires off at once unless you have a super memory and can remember where every plug wire connected to the distributor. The idea is to do one at a time, matching the new wires with the old according to length. If the leads aren't connected to the right terminals, the engine probably will run worse than it did before the project or maybe it won't run at all because the sparks are going to the wrong cylinders at the wrong time.

The tools necessary include, but are not limited to, a half-inch ratchet drive, a spark-plug socket that has a rubber retainer to hold the plug, probably a flexible drive coupling for working in areas that provide less than a straight shot to get to the plug, socket extensions and maybe needlenose pliers to pull out any debris that may be in the plug well. Other handy items include a small stepladder to enable access to areas that the arms can't reach with the feet on the ground and a cloth shield to keep belt buckles and dropped tools and plugs from damaging the vehicle's paint.



Make sure that there is no debris in the plug well that could fall into the combustion chamber before the old plug is removed. The small mirror on the rod comes in handy here, particularly for those plugs that are hidden from direct view. If you have an air compressor, blow air into the plug well to dislodge any debris and use protective eyewear to keep anything dislodged from the plug wells from ending up in the corneas. If you don't have a compressor, try using a narrow paint brush and dry swabbing the area. If there's anything there, you'll feel or hear it.

Take your pick on where to start, though a proactive thought is to start with what looks like the worst of the bunch. That way, you'll get the bulk of any frustration out of the way early in the game. Also, it's a good idea to do one plug at a time to avoid confusion on what wire went where and to wait for the engine to cool.

To begin, remove the plug wire and place the plug socket over the plug and unscrew it. That should be simple enough, though make an effort to keep the socket as straight as possible to keep from cracking the plug's insulating porcelain, shards of which could fall into the combustion chamber. If you hear a crunch, stop and clean out the plug well.

Take the new plug and start the threads by hand, if possible, to make sure that anything doesn't get cross-threaded.

On replacement, if you need to use the socket because there isn't room for the fingers, place the new plug into the socket and lower it into the plug well. With a socket extension and not using the ratchet, start screwing the plug into its place, again slowly and without pressure, until you're sure that the threads match. Then use the ratchet to tighten the plug into its seat.

If you're replacing the wires along with the plugs, follow the same route with the new wires that the old ones used, including through the wire retainers the manufacturer put there to keep the plug wires out of the way.

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