Knowing that there was little cushion in this job, we checked compression as well as the ignition components to prevent being caught off guard when the gasket was replaced. When we were sure the miss would be repaired, and that the car would certainly run better with the manifold gasket, we got the authorization to replace the gasket and install a much needed set of spark plugs. With the gasket replaced and the engine running smoothly, we checked output of the rear O2 sensor, and it looked to be operating as expected in spite of the exhaust leak. With our budget constraints in mind, while we were aware of the fact that fresh air entering the exhaust system could lead to an O2 code, we set out to run the monitors in an attempt to get the car through state inspection, giving the customer some time to budget for the additional necessary repairs.

KEEP YOUR SCAN TOOL HANDY
Experience has taught us that the Hyundai line of cars can be a bit of a challenge when it comes to setting monitors, and it really pays off to be sure the setting criteria is met. We’ve gotten in the habit of having the scanner hooked up whenever we’re road-testing a driveability problem or setting monitors to confirm setting criteria.

In the case of the Elantra, we were looking for a starting coolant temp below 104 with a gain to 120 before the test would run. There are additional ­parameters that have to be met, depending on the monitor, and it’s well worth the time to look them up on your preferred service information system. The ECU knows nothing about close enough; if it’s looking for 104 degrees, 105 won’t do. The test will not be run. Some tests will look for a higher temp before the test is run. If the thermostat doesn’t let it get there, you’re wasting your time trying to run the test. I don’t know about you, but I can’t tell a 10-degree difference on the average temp gauge.

There are other advantages to driving with the scan tool. When I’m on the road, I like to keep an eye on the fuel trim numbers, as well as the calculated load. Fuel trim is the window into what the fuel control is doing; when you come right down to it, all it can do is add or remove fuel. If you’re seeing the short-term being adjusted, with the long-term chasing it and it’s staying near zero, you can’t ask for much more than that.

Calculated load tells us just what it says it does; it’s a window to the load the driver is applying. I ­always do a full throttle uphill pull and look for 100 percent load. If not, it’s a good bet that the mass air sensor is dirty, the intake hose is cracked or the throttle switch isn’t seeing wide open.

BACK TO THE ELANTRA — OXYGEN SENSOR CODE
While the car ran well, it took only a couple of drives before we had the O2 code back. If you monitored the front O2 signal, it appeared to be switching well but was hard to tell if they were all within a second. Knowing that the exhaust leak could be an issue, we replaced the flex section of the pipe. With the now-quiet exhaust system, the signal from the O2 looked better and it took longer for the code to set, but set it did. At this point, we were back to our service info as well as checking for issues on iATN, something that should have been one of our first steps.

A quick search on iATN covered the things we ­already did, but it also mentioned problems with the grounding of the alternator bracket to the block, as well as the engine ground and body grounds near the battery. I’d like to say that I know exactly how the bad grounds ­affected the O2 readings, but I’m afraid I can’t. I can say, however, that after we cleaned the grounds the car set the monitors in two trips, and we had a successful repair and happy customer who no longer talks about needing a new car.

There are some other common failures with the Hyundai line of vehicles, but none are what could be considered pattern failures. We’ve had problems with coils and ignition wires that leak spark when damp after they see some miles, and engine coolant temp sensors that fail over time. There have also been some problems with wiring harnesses that can be tough to track down and should be kept in mind as you diagnose driveability issues. And these cars, while very reliable, aren’t immune to the same lack of maintenance problems that we see on other makes we service. Fairly common are things like mass air sensors ­becoming contaminated as a result of low-quality or dirty air filters, and cracked intake hoses that can ­result in stumbles and low-power complaints. And, don’t overlook the basics like the spark plugs.

SERVICE INFORMATION
One thing is clearly apparent as we work to diagnose and repair driveability and emissions problems: The correct information to do the job is just as important as any scanner or scope. As with my example above, access to community forums like iATN can prove to be ­invaluable. In addition, Hyundai has made its service information website a free service, so there’s no reason not to register at www.hmaservice.com and take advantage of the information that’s available.

Even more important is regularly making use of service information as part of your diagnostic strategy. Get in the habit of checking available information, whether it’s service tips like the ground problems that got us out of a tough situation with the Elantra, or knowing the criteria the ECU is looking for to set the code you’re chasing. Arming yourself with this information, and combining it with your personal experience and skills, will let you repair any car including the fine line of Hyundai vehicles in a professional and efficient manner.