IGNITION-RELATED DILEMMAS
Another system that may give you some problems is the ignition. With the popular twin-cam engines, Mazda is able to use a central plug location. Of course, to accomplish this there is a spark plug tube cast into the cylinder head that is sealed from motor oil on the top by the cam or valve cover gaskets. Since Mazdas have gone to hydraulic valves, the valve cover gaskets are not replaced on a regular basis. When these gaskets leak, you will find the end of the plug wires soaked with motor oil when they are removed. If allowed to get deep enough, the oil will create a path to ground, shorting out the spark and resulting in a miss.

If you find this condition while you’re performing a service procedure, remember that even a small amount of oil in the cylinder will affect your compression reading. Even if there is no sign of leakage, it’s important that you take a good, hard look at the insulators on the end of the plug wires. Look for pinholes and the associated discoloration that would indicate that the spark is jumping from the wire to the nearby cylinder head. Be sure to check the distributor cap and rotor for spark leakage. These cars run for many miles with very little service. If you’re presented with a high-mileage vehicle or a complaint of "poor run in the wet," it would be wise to replace the cap rotor and wires with high-quality replacements.

Bad plug wires seem to create more problems on Mazdas than on some other brands. If you’re diagnosing a driveability complaint, check the plug wires first. Even if there is no apparent misfire, an open plug wire will send electrical forces bouncing around under the hood, causing driveability problems you wouldn’t expect from a bad wire.

The other weak link in the ignition system is the distributor itself. You may have a complaint that the car cut out but when started back up, it seemed fine. Or maybe it just cut out and wouldn’t start. There are no serviceable parts in the Mazda distributor, so if we have a no-spark condition that is traced to one of the components housed in the distributor, the unit will have to be replaced.

Actually, on some models, the igniter is available but it costs as much as a rebuilt distributor. The aftermarket has good, rebuilt units available. There is one thing to note on the rebuilt units - they all don’t come with the O-ring. You may be able to carefully switch the old one, but it’s much safer to have a new one on hand. When the time comes to put the timing light on, be sure to check your service information for any special procedure required to set the base timing.

Of course, in order to produce a spark, the distributor has to be turning. Being that these models have timing belt-equipped motors, a big part of your underhood maintenance procedures will be servicing timing belts. I won’t go into the nuts and bolts of replacing the belt, but know that there are no surprises when servicing timing belts on Mazdas. You have to be sure that the tensioner and idler pulleys are in good shape. There have been some problems with MPVs where the belt will contact the front cover, a sure sign that one of the pulleys isn’t pushing straight. There are bushings available for some applications.

Another problem that shows up mostly on the older cars is a damaged crank or camshaft pulley and keyway that will allow the cam timing to get far enough off that you’ll be faced with a no-start condition. Of course, you’ll line up the timing marks and they’ll be right on. But like always, trust your first instinct. Remove the number one plug and bring the piston to TDC. Confirm the mark on the pulley. To check the cam, you can use the ignition rotor. It should be pointing to cylinder one or four. Or remove the valve cover and look at the cam again, looking at cylinder one and four. One of the cylinders should be on overlap (both valves open), while the other will be on TDC (both valves closed). If the pin is sheared in the camshaft, take a good look at the cam bearing caps.

Look for signs of heat damage that may have been caused by lack of lubrication. Depending on how bad the damage is, this car may need more than a timing belt. If the crankshaft key is damaged, more decisions need to be made. Of course, the best way to fix it is to replace the crank and pulley, but, in the real world, that may not be an option.

In most cases, we’ve had good luck with the stud and bearing mount. Be sure to get the parts as clean as possible and torque the crank nut to spec. Let the car sit overnight to allow the chemical to set up. Although it’s not a permanent fix, if all goes well, this procedure will give many more miles of use.

While changing the timing belt, at the minimum, all the drive belts should be replaced. Even though water pumps and leaking seals are not common problems, both should be checked while taking mileage into consideration. 

I guess I should mention the fuel system, but there isn’t much to say. Mazda has done a good job here. Unless you’re in a no-rust zone, all the models you’ll see will be fuel-injected. We already talked about the air intake problems and the dirty air mass sensors. Again, the only other problems are on the older cars, but there are still plenty of them on the road.

If you have a car with a dead cylinder that the injector is not operating on, be sure to check for voltage to the injector before declaring the injector dead. There is a resistor block that drops the voltage to the injectors and these units have been known to fail. The location varies, but it is usually mounted to take advantage of cool air blowing over it.

Of course, there are the usual relays and sensors that can give us trouble on a vehicle-to-vehicle basis, but no pattern failures that I can identify. Maintain the system by changing the fuel filter at recommended intervals.

We can’t talk about underhood service without discussing check engine lights. Hopefully your shop has made the investment in a scanner with Asian software. If so, pulling and clearing codes will be no problem.

On the other hand, Mazda has given us ways to pull codes on pre-OBD II cars with a jumper wire and flash codes from the check engine light. For example, on 1994 vehicles, find the diagnostic box under the hood and put a jumper wire between terminal 10 and ground. The check engine lamp will blink out codes. Long flashes are 10s, while short flashes represent single digits. For example, two long flashes and two short flashes would be a code 22. Another thing to keep in mind is that not all of the codes are kept in memory. Some can only be retrieved while the MIL is lit and the engine hasn’t been turned off. If you are lucky enough to get the light to come on during a road test, don’t turn the engine off until you retrieve the codes.

The procedure for clearing codes is also a little different than what we are used to doing. Disconnect the battery and press the brake pedal for 20 seconds. Reconnect the battery, and then reconnect the jumper wire to retrieve codes. Turn on the ignition, but don’t start the car for six seconds. Then, start the engine and run it at 2,000 rpm for three minutes and be sure no codes are displayed. Remember that this is an adaptive system - one that wants to learn how the driver is using the car. Be sure to road test the car after clearing the codes. 

On the early MPVs, the check engine lamp comes on at scheduled intervals. Turning it off requires removal of the instrument cluster and moving screws on the printed circuit. Be careful on vans equipped with automatic transmissions, as the cable for the gear indicator has to be disconnected from the steering column so it is not damaged when the cluster comes out.

We’re about ready to close the hood on this Mazda and get on with the next job, but first we have to finish up this job. Have we checked all the fluid levels? Do the battery cables need service? How about the hood latch, hinges, throttle and shift linkages? Are there any signs of rust that are begging you for a squirt of lubrication? Did you do an oil service? How about the transaxle level? Some of these cars require that you remove the speedometer drive to check it.  I hope these tips make your job of servicing Mazdas with great efficiency a bit easier.

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