Marinucci: Clues could solve what's bugging vehicle

Automotive service providers should recognize the importance of a thorough visual inspection when troubleshooting customers' complaints.

Time and again, visual checks have revealed a clue that ends up solving the mystery of the vehicle's condition. One simple detail — perhaps something that looks odd or unusual — steers a technician on the right path.

Mind you, visual clues make a tech suspicious of a problem. Thereafter, an accurate diagnosis should confirm those suspicions.

To put it another way, capitalizing on visual clues may spell the difference between working hard and working smart.

Working smart enhances the chances of repairing a vehicle properly the first time.

Typically, "fixed right the first time" sits atop — or ranks very high on — motorists' list of auto service expectations.

Remember that effective visual inspections require a certain level of curiosity and open-mindedness. After all, evidence such as dirt, stains, fluid seepage, etc., could pique the interest of one tech but elude another.

Similarly, evidence of bees and spiders may raise diagnostic flags for some but not all techs. But as you will see in a moment, "critter-like" clues may save you the blues. Here are examples borne of personal experience.

The owner of a Toyota Corolla said he could not fill its gas tank completely. He found himself relying on a partial tank of fuel; no one could explain the cause of this odd symptom.

The Corolla's engine control computer (ECM) had not stored any trouble codes.

Photo 1 shows the end of an evaporative emission hose located under the rear of the Corolla. During the 2000s, thousands of Toyota vehicles were equipped with that hose setup.

The tip of this hose normally has been cut at an obvious angle. But what is decidedly abnormal here is the blob of thick, white material filling the end of the hose. I suspected that this was remnants of a spider's nest.

Standard leak-test procedures for this evaporative emission system require temporarily plugging or crimping off this hose.

Fortunately, the Toyota ace who taught the system to me emphasized a potential mistake.

"Remember to unplug the end of the hose after the leak test," he said. "Otherwise, the customer won't be able to fill the gas tank completely!"

Apparently, the white, cobweb-like material constituted an effective plug. Simply cleaning out this evaporative emission system hose fixed the Corolla for good.

A year or so after the Corolla incident, I was helping a pal at a shop in Virginia diagnose a Honda Pilot. The vehicle had an evaporative emission trouble code stored.

To make a long and complicated story short, I began my visual inspection at the top of the Pilot's engine compartment.

After removing a large, decorative cover from the top of the engine, I saw telltale mud deposits on the engine. Previously, local techs had warned me that these deposits indicated the presence of critters called mud daubers.

The mud dauber, a wasp that makes mud nests, is more prevalent in the hotter regions of the country.

I noticed an evaporative system hose on the Pilot's firewall, not far from the mud spots. Basically, this hose performed the same task on the Pilot that the other hose performed on the Corolla.

Next, I raised the Pilot on the lift and traced the hose from the firewall downward. I disconnected the hose from the rest of the "evap" system. Next, I used a diagnostic smoke-producing machine to push smoke up through this hose — no luck.

Finally, I gave the hose a brief blast of low-pressure compressed air. Suddenly I could hear compressed air rushing up through the hose. A second smoke check showed that the diagnostic smoke flowed freely through the hose in the engine bay.

I reconnected the hose to the evaporative system and erased the trouble code. We invited the Pilot's owner, a regular customer, to drive the vehicle and report back to us.

Clearing that section of hose with compressed air eliminated the trouble code for good.

From my vantage point under the Pilot, I could not see if the compressed air actually dislodged mud. But I strongly suspected that it did.

The key takeaway this time is that potentially elusive problems may "bug" your techs if they do not look for it carefully.