Service Slants

Motor, Oct 2005 by Rosario, Tom

Mazda

No 5th gear or Reverse engagement. The owner of a 1999-2003 Miata with a six-speed manual transmission may come into your shop complaining that he can't get the box into 5th or Reverse gear. If he does, ask if he had the transmission fluid checked or changed recently. If he answers in the affirmative, there's a good chance an inexperienced tech handled the job-with dire consequences. Here's why:

As the illustrations below clearly show, the transmission case on the Miata six-speed has several different plugs. The 8mm hex plug on the right side of the case is part of the crank lever shaft, which retains the 5th/Reverse counter lever. Remove that plug and the lever shaft comes out with it, causing the counter lever to drop to the bottom of the case. The result is that both 5th and Reverse gears go south. And the only way to get them back is to pull and disassemble the transmission!

Now look at the left side of the case. Here you'll find two 24mm plugs. As you can see, the fill plug is at the midway point, the drain plug at the bottom. This is where you want to be when doing any kind of maintenance work on a Miata six-speed.

Ford/Ford Truck

Engine ticking noise. Owners of 2001-04 Ford cars and light trucks with a Romeo-built, two-valve 4.6L V8 may come into your shop complaining of an irritating ticking sound from the engine while it idles. According to Ford, the noise affects only engines built before 9/17/03, usually emanates from the valve guide area at the rear of the cylinder head(s) and is more pronounced at the front wheel wells rather than under the hood. Carbon buildup in the rear exhaust guides is the ultimate villain. New-design complete cylinder head and cam assemblies (Part No. 4L3Z-6049-AA, right; 4L3Z-6049-BA, left) are now available to solve the problem.

Of course, these new parts don't come cheap, so Ford suggests a little detective work before proceeding. Start by using a stethoscope to verify that the noise is indeed coming from the rear of the cylinder head(s), near the exhaust ports. If it's not, seek other remedies; this information doesn't apply. Next, get underneath the vehicle and make sure the noise is most prominent in the exhaust, or in the area of the catalytic converter. If it is, start unplugging the injectors one at a time. If the noise diminishes or goes away, you'll have to look elsewhere for a remedy. If it doesn't, remove the valve cover on the affected cylinder head(s) for a more in-depth look.

At this point, you'll want to make sure that the cam spacers are properly positioned, the cam sprocket bolt is tight (retorque it if necessary) and the hydraulic lifters aren't spongy or collapsed. You'll also want to verify that the timing chain tensioner pin has been removed. If the noise remains after this diagnostic routine, go ahead and install the new-design cylinder head(s) with confidence.

The following vehicles can benefit from the upgraded heads: 2001-04 Mercury Grand Marquis, Lincoln Town Cars and Ford Crown Victorias, Mustangs, E-Series vans, Expeditions and F-150 pickups; and 2002-04 Ford Explorers and Mercury Mountaineers.

GM

Droning noise. Some 1999-2002 Chevy Cavaliers and Pontiac Sunfires with the 2.2L Four (VIN 4) can produce an annoying droning sound from under the hood. GM says the noise is most obvious in hot ambient temperatures, with the engine idling and the a/c on. A resonance setting up in the span of the accessory drive belt between the a/c compressor and alternator is the likely cause of the irritation. Installing a new-design drive belt (Part No. 12575450) made of a different material with a higher natural frequency should cancel out the resonant noise and satisfy your customers.

Ford

Detonation on acceleration. According to Ford, some 1998-99 Crown Victoria and Grand Marquis models may produce a knocking or pinging noise under heavy acceleration when outside temperatures are above 90°F. The cause of the detonation, says the carmaker, could be improper cooling fan operation and/or too much spark advance commanded by the PCM.

Start your diagnosis by pulling and addressing all DTCs. If no codes are stored, use the bidirectional controls on your scanner to activate the fan motor-first on low speed, then on high speed. If neither speed works, repair problems in the affected circuit, then take the vehicle on a long road test to see if the detonation problem has been resolved.

If it hasn't, you'll have to reprogram the PCM with fresh software files. Here are the updated calibrations you'll need:

Tear tag No. NGS/WDS Qualifier

FJB1, FJB2 ................9VNA-AK

JCA1, JCA2 ...............9VNA-AL

VTC0, VWN0 ..................8-18F

XDX0, KCL0 ..................8-18H

After the PCM has been flashed, take to the open road once again to verify that the pinging or knocking sound has been eliminated. If it hasn't, you're going to have to retard the base ignition timing by performing what Ford calls a "Software Octane Adjust Procedure." To do it, follow the steps outlined in the NGS operating manual.