An expensive date with Miss DiagnosisWritten by Nick Shultz | | email@example.com
I have mentioned it in the past, and now might be a good time to repeat it.
“I am sure your neighbors’ son is a wonderful young man. That does not make him an automotive technician.” My neighbor, who is a great guy, learned this lesson the hard way.
My neighbors’ nephew, Justin, is learning to fix cars in his dad’s garage. Justin is a handy young man. He has leaned over a fender more than once watching me work and has handed me tools in the past. He is a good worker. Not unlike a lot of folks these days, Justin is laid off from his main job. Justin is picking up extra money “twisting wrenches” in his dad’s garage. So when my neighbor’s pickup truck began “blowing black smoke” he thought of his nephew Justin. Since my neighbor is also laid off from his job, I can understand why he wanted to save money on the repair. Justin stopped by my place and told me of his uncle’s problem and wondered if he could borrow my Scan tool. A Scan tool is a device that allows a technician to interface (speak) with the vehicle’s onboard computers. I had showed him how to use it on several occasions and was comfortable he would be able to scan his uncle’s truck.
It all appeared very innocent and logical at first glance. Things went downhill and got very ugly in a hurry.
Because my neighbor’s pickup truck is several years old, it does not have the latest computer technology on board. It does, nonetheless, have a computer-controlled fuel delivery and spark-timing system. Therefore, the truck’s computer system will store diagnostic trouble codes relating to suspected problem areas. A trouble code was stored within the computer’s memory, indicating a problem with the manifold vacuum sensor circuit. The vacuum sensor was indicating low-engine vacuum.
Justin went to our local parts supplier in town and told them which code he had retrieved. The parts supplier then sold him a new manifold vacuum sensor along with a new set of spark plugs. The bill came to about $100 for the parts. Justin installed the new parts and was en route to his uncle’s house to collect his money when he noticed the lack of power from the engine and black smoke coming from the tail pipe. The original problem still existed. He turned around and headed back to his dad’s garage.
Justin pulled the new spark plugs and found they were caked black with soot. He cleaned and reinstalled them. Justin told me he said to himself at that time “this truck’s running very rich.” Justin then convinced himself, and his uncle, that the fuel injector system was at fault. He drove back to the parts house and bought a fuel pressure regulator and a can of injector cleaner. Another $75 was spent.
After the new parts were installed, the truck still blew black smoke and lacked power. Justin, his dad, my neighbor and the retired man down the road spent the next two days and about $200 more attempting to fix the problem.
That’s when I got the call from my neighbor. It went something like this: “Nick, I’ve got nearly $400 wrapped up in this darn truck and it still is blowing black smoke. Could you stop by and look at it for me?”
Justin was slumped at the shoulders and looking like he had lost his best friend when I walked into his dad’s garage. My neighbor was standing with his arms crossed, and it was obvious he was not happy. Justin’s mom rushed out of the house offering me a glass of iced tea; however, it was clear her main purpose was to protect Justin from any more wrath.
Justin’s dad was sitting in a lawn chair drinking a beer, helping the retired man down the road decipher information from a repair manual that he picked up from the local library. Another fella I recognized as one of the counter people at the parts house was leaning on the fender of the truck. Parts and tools were lying everywhere.
“So what have we found out so far” I quierried. Four voices rang out all at once. Only Justin remained silent. It became quite clear that no one was sure what had been checked and what hadn’t been checked. The only thing clear was everyone was blaming Justin for the mess.
“Justin, it’s time you learned about the three B’s of automotive repair,” I told him. “I didn’t Build it; I didn’t Buy it; and I didn’t Break it.”
I was looking more at the four men in the room than at Justin when I said it.
After a few questions directed to the four men in the room, I came to realize that they all were convinced the problem was in the computer system. Not one of them had considered anything else. The only thing that was clear regarding their diagnosis was the manifold vacuum sensor was still throwing a code. It was still indicating low-engine vacuum. No one had actually checked engine vacuum, however.
I asked Justin if he had a vacuum gauge, and he did. I hooked it up to the engine and started the truck. Vacuum was very low. A quick trip back to my house for a compression gauge while Justin pulled the spark plugs and a half hour later, I diagnosed the problem. The engine had jumped time. Everything that had been replaced so far was only a symptom of the actual problem. The computer control system was doing exactly what it was designed to do. The core issue was the defective timing chain.
Another $150 and several hours of Justin’s time later, the vehicle was running just fine.
Justin and my neighbor had their first date with Miss Diagnosis. Had my neighbor taken the car to a qualified shop he would have saved a lot of money. The relationship between the computerized engine-control system and the base engine is way beyond Justin’s understanding at this time.
The lesson was costly for both of my friends.
I hope none of our readers get caught in the same trap.
Nick Shultz is an instructor of Automotive Technologies at Owens Community College. He is an arbitrator for the Better Business Bureau who specializes in cases involving the Ohio and Michigan Lemon laws. He is a certified master automotive technician by ASE, General Motors Corp. and Ford Motor Co. Shultz, a Toledo native, will take questions from firstname.lastname@example.org.