Tim never thought he would have a problem with fixing cars. He had a knack for finding the problem, usually within the first few moments and considered himself a very clever mechanic who took pride in his work. People brought their cars to him from every part of town and his boss admired his work.
Just about the time you think you've got it all figured out, along comes a problem car that refuses to be fixed. This happens to every mechanic who has been around the business for any length of time. It's as if the gremlin of car problems sends a tough one your way just to keep you on your toes and knock you down a peg or two if you are getting too cocky.
The time was right for Tim to get put in his place by that gremlin. The car was a late 80's Camry and it had a multitude of seemingly unrelated problems. The owner insisted that all the problems started after he tuned it up. All he had done was slap in a set of plugs, check the timing, change the oil and filters and sent it on its way.
Now it had a bad case of the hesitations. Once it got up to speed, it performed just fine. Also, it kept running down the battery and was hard to start. As soon as the car was back in his stall, he checked for stored codes in the computer.
There were no codes. One thing he did notice was the radiator cooling fan kept running, even though the temperature gauge was in the normal range.
He decided to check a wiring diagram to find out what would make the cooling fan run all the time. He kept asking himself, "Why me, what did I do to deserve this?" The wiring diagram wasn't much help. The cooling fan running all the time seemed to escape logic -- at least as far as he could tell from the wiring diagram.
For some reason Tim decided to start with the thermal sensing switch. As luck would have it, when he grounded the wire going to the switch, the fan stopped running. Closer inspection of the wiring connector turned up a clue. The connector had been wallowed out and was probably not even touching the switch.
Using needle-nose pliers, he tightened the connector and plugged it back onto the switch. To his relief, the fan quit running.
What about the car's new-found hesitation? Maybe a good 'ol injection cleaning was in order. An hour later, after hooking up the cleaner and giving the injectors a good dose of cleaning solvent, the problem remained unchanged.
"Maybe it has something to do with the timing?" he thought. He tried bumping the timing up and back a few degrees, both without any real effect.
"How about an exhaust restriction?" he thought. Minutes later he was under the car breaking loose the catalyst. A test drive revealed no change. "What would my vo-tech teacher say? What would he tell me to do? Probably say, 'back to basics boy'." Okay. Back to the basics. After checking the compression, he spent the rest of the day with the scope and exhaust analyzer.
Maybe it was a lazy oxygen sensor. He ordered a new one and decided to call it a day. On his way home, he was going to stop in and ask his friend, Sid, about the car. Sid was a Toyota specialist. Tim was glad he stopped and talked with Sid because he was given a whole laundry list of things to check. He could hardly wait until the next day to dig in again.
First he replaced the O2 sensor, but it only helped a little, but the sag was definitely still there. Going down the list, he removed and checked the air boot between the vane air flow meter and the throttle body. No cracks. Next he carefully removed and cleaned all the engine compartment wiring connectors, paying special attention to the one under the battery and on the airflow meter.
Still, the test drive proved nothing had changed.
"What about the vane airflow meter itself?" he thought. He took it off and inspected the action of the air door. Even though it didn't hang up or have any roughness in its movement, he decided it should be replaced.
Later that day with the new airflow meter secured in place, the problem persisted. "It must be the stupid computer after all," he reasoned. The following day he installed a new computer and found out his hunches were still wrong, wrong, wrong.
The car owner was getting really mad about all the time he was taking with the car and was making nasty threats to his boss. The boss was getting very testy, especially since Tim had already sunk a small fortune in trying to capture the Camry's evasive gremlin. Tim decided to pay Sid another visit.
Sid said it sounded like a carbon problem. "Camry's are supposed to grow carbon in the combustion chamber, intake manifold and intake valves. Pull the manifold and clean all the carbon out.
It's probably full of carbon." Sid was right about the carbon. It had a good share of it, especially on the intake valves. Using spray carb cleaner and several small wire brushes he was able to clean the intake area pretty good without having to remove the cylinder heads. He figured he had it for sure this time.
"Wrong again honey!" he said out loud as he stepped on the gas and the car lost power.
"Man, this one has really got me down... time to pay Sid another visit, this time with the car!"
Sid's mouth dropped open when he saw him pull up in the car with a sour look on his face. As Tim got out of the car he held up a thumbs-down sign.
At first Sid was speechless. "Nothing has helped? You did everything I suggested?" Tim replied, "Nothing. Nada. Nix. Zip. Zilch."
Suddenly Sid's face brightened. "Let me look at the rotor." Tim said,
"Sid, this is not an ignition problem. The stinkin' car just hesitates -- and is a bear to get started when it is cold. Maybe the cold start injector, maybe the throttle position sensor. But why the rotor?"
Sid replied "Just a hunch..."
Sid unscrewed the distributor cap mounting bolts and grabbed a jumper lead from his box. He clipped one end of the jumper to the coil secondary terminal and held the other end just above the center of the distributor rotor.
"Crank it over!" he yelled. Tim twisted the ignition key while the starter motor cranked.
"Hold it!" shouted Sid. "Come check this out."
"Here, Tim, hold this lead just above the rotor. Now I'm going to crank the starter. You watch for a spark."
Tim said "Yep, got a spark. So what? I know the spark is good."
Sid countered, "Yeah, but the rotor isn't supposed to conduct like that. It's grounded right through to the distributor shaft.” “Look,” he said as he pulled the rotor from its place and examined the underside.
Sure enough there was the faintest trace of rust where it mounted on the shaft.
"But how can that cause hesitation?" Tim asked.
"Easy," Sid replied. "When you give it the gas, there is a need for more spark to fire the richer mixture. The extra resistance in the spark plug gap makes the secondary seek another path to ground. The rotor leaks just enough voltage to cause a slight misfire and hesitation."
"And when I hook it up to the scope, everything's normal because it isn't under load," said Tim.
Sid reached into a top drawer and pulled out a used rotor and gave it to Tim. "Here, lets put this back in the car and you take it for a spin and see if the problem is gone. If not, come right back." Tim didn't return.
The car owner was charged for the injector cleaning, carbon removal, distributor cap, rotor and oxygen sensor. His boss put the computer and airflow meter somewhere in the stock room, hopefully for some future need. Tim got paid two hours for his efforts and went home with a lesson he will never forget. Chalk one up to the car gremlin.
