One of the daily challenges that we face at our shops is diagnosing and fixing automotive problems that arise only intermittently. Drivers come to us all the time asking us to fix vibrations, noises and poor-running or no-start conditions that happen sometimes, for unknown reasons.
There are four logical steps to any kind of problem solving in any field.
The first is to observe and experience the symptoms of the problem.
Step two is establishing a theory about the root causes of the problem.
Moving to step three, you test, review and diagnose to prove or disprove your theory.
The fourth and most important step is applying a remedy — in the case of auto service, repairing or replacing the parts in question — to make sure your theory is correct.
If the problem does not exist all the time, however, you lose control over two or three of these steps.We have had vehicles that will crank over but won’t start.
One of the first steps in this case is to read the onboard ECU (electronic control unit) to see if any fault codes have registered. If they have, we consider whether the no-start condition can be attributed to those systems or components. To complicate matters more, many no-start problems such as an intermittently bad fuel pump don’t send a fault code to the computer. In the case of a bad intermittent fuel pump, we can’t experience the problem unless it happens to fail on us, we can’t test the problem and we can’t completely verify the condition until a new pump is installed and the vehicle is back on the road with no continuing issues. Noises and vibrations are a tough fix, too, because you have to experience them to repair them. Sometimes a customer just has to be patient until the intermittent problem becomes more common or the source is pinpointed. With an intermittent no-start condition, a customer should understand that the problem might not be repaired on first attempt. Sometimes a logical solution such as a new part might not fix the problem, and in such a case the procedure becomes part of a process of elimination. Keep in mind that, despite occasional problems, a modern vehicle is the most advanced item most people own — a moving, highly technical marvel.