Repair And Fix it

Like most ponderings in automotive repair, the question of removing spark plug wires from a running engine isnt necessarily so much one of "could" as it is of "should." Technically, yes, you can yank the plug wires off of a running engine just as easily as you could one that isnt running, but it may not necessarily prove conducive to you or your cars good health.

You Could

Removing a plug wire from a running engine isnt likely to result in catastrophic engine failure, particularly if you put it back on shortly afterward. All spark plugs misfire from time to time, you just dont notice it because its intermittent, random and usually happens so quickly that the cylinders firing again before the engine has a chance to vibrate. So, intentionally creating a misfire by removing the plug wire for a few seconds or even a few minutes isnt likely to destroy anything on most engines.

Common Effects on the Engine

Most engines have a rubber ring on the front of the crankshaft called a harmonic balancer; on the outer edge of the balancer is a heavy, metal ring. When the explosions in the engines cylinders push down on the pistons, the forces they exert quickly accelerate the crankshaft. When that accelerations over, the crank tries to slow down, resulting in a constant cycle of acceleration and deceleration that manifests as vibration in the crankshaft. The metal ring on the balancer resists these sudden, but tiny, vibrations and keep the crank from tearing itself in two. Over a long enough period of time, a dead cylinder and the resultant heavy vibration will over-work the balancer, causing it to fail. Once that happens, you could be looking at serious damage to the engine.

Effects on the Converter

Your cars catalytic converter works something like a blast furnace to convert toxic gases produced by your engine into more inert forms that wont drown polar bears or grow fish with three eyes. The converter takes advantage of unburned fuel -- which is, itself, a pollutant -- coming from your engine and uses it to fuel the furnace in the converter matrix. More fuel means more heat. Killing the spark in one cylinder will drastically increase the amount of fuel pouring into your exhaust, which will, at some point, cause the converter to overheat and fail. The engines control computer will compensate for this to some extent, but you can count on extra fuel going into the exhaust.

Lean-Out

Depending upon the computers control strategy, disconnecting a plug wire and leaving it that way could seriously fry something. When the oxygen sensor detects excess fuel in the exhaust, your cars computer may assume that this represents a net excess of fuel through all the cylinders. It will respond by decreasing the amount of fuel injected to all of the other cylinders in order to get the air/fuel ratio back in line. The resulting lean condition will increase combustion chamber temperature, causing overheating, detonation in the engine and, eventually, complete meltdown. Most computers do have programming provisions to account for a dead cylinder, and wont react this way; but some dont, and theres no way to be sure unless you know exactly how your fuel injection system thinks.

Safety Issues

Before pulling the plug wire off of a running engine, bear in mind that your are, in fact, grabbing a live wire with about 40,000 volts worth of electricity coursing through it. Normally, this electricity will pass through the plug wire and race to the spark plug, which acts as a ground. But when you remove that ground, the spark is going to find the next, most convenient ground. If you happen to be touching the body of the car when you pull the wire off, then you become that ground. While electricity normally wouldnt arc through the insulation, even if it is a bit old and damaged, removing the primary ground will make that spark pretty determined to get out whatever way it can. Its not likely to kill you unless you have heart or nervous system problems, since the amperage is very low -- but the sensation is rather, shall we say, "life affirming."

While a vehicle with a cracked radiator remains operable and can be driven as long as you ensure it remains continually full of water, doing so is not a good idea. The radiator and the coolant that it holds performs a number of crucial functions for proper engine operation. A crack in the radiator will reduce pressure, introduce air into the system and foul the ground with poison. Even if you stop to fill the radiator regularly, the breach in the system will ultimately affect the engine overall.

Overheating

The primary purpose of a radiator is to cool the engine. When a radiator is cracked, coolant leaks from the radiator, causing the level to fall, resulting in improper cooling or a complete loss of cooling. Overheating an engine can result in a damaged or ruined engine.

Loss of Lubrication

In addition to cooling the engine, antifreeze lubricates the water pump. When the radiator is low on antifreeze or even filled with just water, no coolant, the water pump is not properly being lubricated, which can cause premature pump failure.

Expense

While the primary reason that one might choose to drive with a cracked radiator is to avoid the cost of repair or replacement, the costs of antifreeze and damage to the vehicle will far outweigh any short-term savings. To save money, a car owner may choose to repair the damaged radiator or to purchase a used one.

A good diagnostician is something of a Car Whisperer, one who can pick up on the tiniest of clues to intuit both the cause of a problem and the avenue to its solution. Tire cupping isnt the most common wear pattern out there, but it is one of the most serious and telling in terms of diagnosing the chassis condition.

Cupping

In terms of tire wear patterns, "cupping" ers to a series of regular dips appearing in the outer edge of a tires tread. Also called "scalloping," these dips look as though someones taken shallow scoops out of the rubber with the worlds most sinister ice cream scooper. This sort of cupping shouldnt be confused with the cupping that often occurs on large drag tires. In this context, cupping happens when the tires inflation pressure is too low and the center of the tire curves upward or "cups" at high speed.

Cupping Causes

Cupping is a sign of rapid tire bounce or side-to-side oscillation. Theres no one single cause behind such bouncing or oscillations; any component that connects the wheel to the car is suspect. Worn shock absorbers will fail to control wheel movement, allowing the tires to bounce and cup the tread. Suspension bushings and ball joints are secondary suspects, followed by wheel bearings and steering end-links. The last two, however, should exhibit noticeable symptoms -- vibration through the steering wheel and chassis -- well before cupping becomes an issue.

Argument 1 -- Driving on Cupped Tires

Some contend that cupping isnt necessarily a death sentence for tires, provided that the lowest point in the scallops dont extend past the tires lowest safe wear zone. After youve fixed whats causing the cupping, the high points in the scallops will wear far more quickly than the low points, which should smooth them out over time. Rotating the tires may help to speed the smoothing, since doing so will at least change the frequency of oscillation acting upon that tire.

Argument 2 -- Not Driving on Cupped Tires

While it is true that fixing the problem and driving on cupped tires may eventually smooth them out, the fact is that the low points in the scallops will continue to wear just like the high points. Granted, theyll wear more slowly, but even with the best-case scenario, youre looking at a tire with a serious -- if smooth -- bald strip around the edge. From this perspective, any cupping at all is the death knell for your tire and a sign that it needs replacement ASAP.

Conclusion

Provided that youve replaced the worn shocks, bushings or relevant suspension component, driving on a cupped tire will eventually smooth it out to some extent. But thats like saying that sooner or later the wind will eventually erode mountains. True, it will, but itll also erode the valleys between the mountains and create low-lying dips in the landscape. Its a game of time and specific conditions, and one youre probably going to lose. Considering the likelihood and consequences of tire failure after cupping, youre best off replacing the cupped tire sooner rather than later.

If your vehicle isnt starting when the engine is turning over, you may not be getting spark to the spark plugs through the ignition coil. You can check this by performing a simple test. This task is relatively easy but you will need an assistant so that you can simultaneously perform some of the necessary functions detailed in the procedure. Figuring out the cause of the problem that you are experiencing with your vehicle is half the battle.

Instructions

1

Park your vehicle on a flat surface.

2

Open your hood to access your engine compartment.

3

Pull the nearest spark plug wire off the top of the spark plug to expose the end of the wire

4

Connect the exposed end of the wire to the top of an extra spark plug. Set the spark plug against one of the metal surfaces on the engine.

5

Ask your assistant to start the vehicle. If you see a spark come from the spark plug, then there is spark coming from the ignition coil because the wire is attached to the ignition coil.