Worn distributor bushings may be the culprit

by Jim Kerr . Jun 24 2016

Question: I took my 1966 Dodge Charger classic car out of storage for the summer, and it isn’t running very well. It has a 318-cubic-inch V-8 engine with two-barrel carb and an automatic transmission. A friend rebuilt the carburetor, and that seems to be working fine, but it idles rough. I have changed spark plugs, plug wires and distributor cap, but when I go to set the engine ignition timing, the marks keep bouncing around. I don’t know what to do to fix it, and most garages around only work on newer vehicles. The car is all-original. Can you suggest what to do?

— Gail

Answer: From your description, I can think of two common problems that can cause your vehicle to idle rough and the ignition timing to be erratic. Your distributor has a set of points (a mechanical switch) that close and open eight times per revolution of the shaft to fire the ignition coil. When the distributor bushings are worn, the point’s opening and closing times become erratic, and so does the ignition timing.

You can check the distributor bushings by removing the distributor and wiggling the shaft by hand sideways in the distributor housing. If it moves more than a few thousandths of an inch, then the bushings and possibly shaft should be replaced. You can replace the complete distributor with a remanufactured one or even switch to an electronic ignition system from a newer (mid-’70s) engine if desired.

The other potential cause is a worn timing chain. The timing chain drives the camshaft from the crankshaft at the front of the engine. If the chain is worn, not only is cam-shaft timing erratic but so is ignition timing, because the distributor is driven by a gear on the camshaft.

You can check timing chain wear without removing the front engine cover by rotating the crankshaft back and forth by hand and watching how much delay there is before the distributor shaft starts to turn. A worn timing chain will let you rotate the crankshaft 10 or more degrees before the distributor moves.

Question: I have a 2010 Toyota Rav 4. Last year, the check engine light, 4x4 light, cruise control light and anti-skid light all came on. I was told it was two oxygen sensors, and they were replaced for $600. A few months later, the lights all came on again and I was told the charcoal canister needed to be replaced for $1,100. The kicker is neither affected the operation of the vehicle, however, I was unable to use cruise control, 4x4 and anti-skid. I feel I’m being forced to replace parts that have nothing to do with the above features — kind of like changing the tires because the air conditioner isn’t working. Are there any other options?

— RJ

Answer: The check-engine light comes on when a vehicle fault occurs that causes excessive exhaust emissions. The standard is 1½ times the regulated emissions level before the light comes on. Cruise control or anti-skid (stability control and ABS) system faults would not cause excessive emissions so shouldn’t turn on the check-engine light. A 4x4 fault could potentially cause excessive emissions if a fault created signals to the powertrain computer showing it may be in a low range.

The oxygen sensors and charcoal canister may have also set codes but not severe enough to turn on the check-engine light. As you already found out, neither of these replacements fixed the problem.

The inoperative cruise control is a symptom of another system fault rather than being a fault in the cruise control itself. For example, a faulty throttle-position sensor on the engine would affect engine driveability, which also turns off the cruise control.

The same could be said for the anti-skid system. Because you have a problem with the 4x4 system, if the computer thinks the vehicle is in low range or cannot determine the range, then it will signal other computers to disable anti-skid and cruise control. These systems are normally not functional by design in many 4x4 vehicles when four-wheel-drive low range is selected.

You need to have your vehicle checked by a good technician who understands the systems and how they interact. I suspect you will find a problem with the sensors on the transfer case that provide the low/high range information to the computer.