Ferreting out faults

One of the most satisfying elements of being a trusted wrench person is the fact that we know what to do when most other folks run out of ideas. That’s why we get paid as well as we do. But no level of success we might enjoy on the shop floor gives us license to be a jerk, and we shouldn’t expect to get paid for every job, particularly when we stop to help somebody.

One day I pulled into the Winn Dixie parking lot to pick up some bananas, and I saw a store employee and a kind gentleman trying to get an elderly lady’s car going with a pair of jumper cables. They all were sweating profusely, and things weren’t going well for them. As I walked by the car, I could hear the starter grunting its best with whatever those cables were feeding it for volts and amps, but there just wasn’t enough wattage flowing to light up that old Buick.

When I made my exit from the store things hadn’t changed, so I moseyed over to look the situation over. The jumper cables they were using looked substantial enough, and it was possible the starter’s life was all but gone. But I asked this frustrated group of three to let me fetch my own jumper cables, promising not to charge them anything for the effort. The eyes of the guy who owned the cables drifted to my ASE shoulder patch, and he shrugged.

Taking the bananas to my vehicle, I put them in the passenger seat and reached into my trunk for my coiled up cables. Heaving them onto my shoulder (it’s the easiest way to carry them), I made my way back across the parking lot to the Buick, where the good Samaritans were disconnecting their colorful, brand new, expensive looking leads. My cables were beat up and homemade, but I had built them out of super heavy stuff back in 1979 for use on big diesel engines down in Texas – and they worked well for that. Fifteen seconds later, the Buick’s starter spun like a new one, and the old car roared to life, raising eyebrows and dropping jaws all around. It’s always fun to surprise folks that way, and that 30-pound set of jumpers has rescued more than a few stranded motorists when second-rate cables just weren’t good enough.The satisfaction I get when I solve somebody’s problem that way is a high that money can’t buy. But in this country (at least in my part of it), there are dwindling numbers of people interested in keeping America’s fleet of vehicles on the road. Most youngsters nowadays want a job where they make $30 an hour for very easy work. A good

technician earns every

penny with his sweat and blood, and we all know that the work we do can be tough, demanding and sometimes thankless (more than a few of us have left the business due to burnout). But the work needs doing nonetheless. There’s quite a lot of it out there for men and women who have the discernment to gather information in real time, sort out that data, exercise integrity and do those seemingly miraculous things other folks simply can’t. When vehicles break down, other things break down by default. Engines and wheels drive this economy.

Shoulders to the Wheel
My gaggle of folks plowed into the summer recently with two engine rebuilds (both on donated trainer cars with smoking, unhealthy engines); a hard-starting, weak-running 2006 Rendezvous; a drooping Town Car with flat rear airbag suspension; and our title vehicle, a 2000 Maxima that didn’t idle worth a toot and was all about overheating. Oh, and there was the 2003 Lexus that had a tire vibration and a noisy left front hub bearing, two Crown Vics, one with that washboard-feeling torque convertor chatter and the other with worn out rear brakes, and, well, the list could go on for a while, not to mention vehicle inspections and oil changes galore. The folks in my shop don’t have time to stand around and talk – in addition to their live work they have NATEF tasks to complete.

A relative of one of our maintenance men purchased the Maxima, and he was concerned that relative had made a mistake. The Maxima’s idle was cyclically rolling with an occasional stall, and I directed a couple of guys to do a visual inspection before we even plugged in the scan tool. Stokes (still a junior in high school, but you’d never know it watching him in the shop) had the perception to recognize a split air inlet tube as the probable cause. He had a good eye; that one was hard to spot because it split right by the throttle body clamp.As we examined the fans, we found a wire pushed back in one of the fan connectors, corrected that, and figured we’d see if that solved the overheating issue. It didn’t. That fan worked fine after our

wire harness repair, but the other fan in that shroud was dead in the water. We couldn’t even power it up separately and make it run, so a new fan was in order. It took a couple of days to get the replacement air inlet tube from Nissan, and the new fans cooled it down.

Low-Riding Town Car
Shawn is another student of mine, a tough 26-year-old ex-Army guy who was driving a Bradley fighting vehicle on the other side of the world a couple of years ago. He plunged with me into troubleshooting the Town Car’s suspension problem. The librarian who owned the 1998 Town Car said she could fiddle with the switch in the trunk when the problem first started and make the airbag system work sometimes. But of late those efforts had failed, and she was riding around on flat springs, which is a bone-jarring proposition.

My 37 years in this field dictates that the component that is in the most hostile environment with the toughest job typically is the one that fails. This personal axiom of mine is a guiding principle, by the way, not a hard and fast precept. In this case, it was wrong. The compressor works very hard and frequently fails on these units. But this one was sound, because with the module connectors and wire map in hand we could trigger the air spring solenoids with a 12-volt feed to open and send a ground signal to the compressor relay coil, thus energizing the compressor. It pumped up the bags in short order and they held air well, so we had eliminated a host of issues right there.

With the EASE Wireless Vehicle Interface connected, we accessed the air suspension system’s DataStream (it only has a few PIDs) and saw the problem right away. According to the display, the Lincoln’s DLC was sporting battery voltage (11.51 with Key On Engine Off), but the module was seeing only 8.6 volts at the same time. The module also had stored a code to this effect.

We found the two 12-volt feeds at the module were strong (grounds were good also), so I priced a $300 air suspension control module out at the Ford dealer and called the librarian with the good/bad news. She gave us the

green light, and another part was ordered.

The Rendezvous This one was a 70,000-mile vehicle with a hard starting power loss issue. Someone in the owner’s local area had charged them $130 to replace the spark plugs, which turned out to be a waste of money. He was paid well, but the owner drove away from that shop with an unfixed Buick Rendezvous.

The P0171 always returned after it was cleared, and the long-term fuel trim (LTFT) numbers were high. A exhaustive check for vacuum leaks (we even used smoke) revealed nothing in the way of unmetered air ingress. The fuel pressure was our logical next target, and the gauge showed anemic fuel pressure halfway between 30 and 40 pounds. Snapping the accelerator would drive the pressure even lower.

The specs for this vehicle indicate that 50 to 60 psi is to be expected, but we didn’t have that. The fuel pump for this one is pricey, and the woman of the house had sticker shock when I sprung it on her. She said she needed to discuss it at home, and wanted me to promise her that this Rendezvous wouldn’t nickel and dime them to death before they paid it off. I was rather quick to point out that I had no way of predicting anything other than the fact that right here, right now, they needed a fuel pump. And so they collectively took a deep breath and waved me ahead.

The Parts Come In The air inlet hose arrived for the Maxima, and Stokes installed it in short order, only to find the idle even rougher than before, with the

MAF hovering between 6 and 8 g/s at hot idle and short-term fuel trims (STFT) in the -25 percent range. That split inlet tube’s air leak had complicated our diagnosis – normal g/s for a V6 engine is around 4 g/s.

Double checking everything, and recognizing the fact that MAF sensors tend to be an epic fail on these cars, we ordered one. When it got there, we saw numbers that initially made good sense – 3.85 g/s, which was just peachy until they started bouncing all over the place from 0.66 to 2.75 back to 3.85 g/s. Even with the throttle held steady at 1,500 rpm, the MAF was wild-carding numbers all over the place and the engine was responding in kind.

This was a total departure from what we had seen with the old sensor (which had since gone back as a core), and the engine ran smooth with the MAF disconnected. We had the parts store bring us a different sensor and replaced it a second time with better results.

Conclusion I don’t know how many times somebody has tried to impress me with the statement that they have a relative who is able to “take a car

apart and put it back together from one end to the other.” Knowing how to disassemble and reassemble is an important aspect of what we do, but what’s even more important is the ability to discern what needs doing so as to repair a car surgically rather than throwing parts at it with reckless abandon.

A good electrical guy knows how to determine if a relay is good or bad, and he can repair a circuit with the right size wire well enough so that the repair looks like factory. A good drivability tech can find a problem even if the scan tool won’t talk to the silver box, and he also understands that you don’t throw an oxygen sensor at a car as soon as you get a P0171. He or she recognizes the fact that recklessly yanking on wire harnesses isn’t a good strategy when fighting an intermittent concern. He understands that replacing the EGR valve isn’t the best first step when troubleshooting a P0401, and he won’t change the wrong catalytic converter when he yanks a P0420.

Jobs like these that fly thick and fast in a shop like mine tend to accelerate learning beyond anything I could cook up on my own. Just about any seasoned guy who has trained a few youngsters to ferret out faults can appreciate that.