Hyundai has done a good job of improving its offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to increase its market share year over year. It’s only a matter of time before you see one of these cars in a bay.
Let’s take a look at the fuel injection system and driveability issues on Hyundai’s line of vehicles. The most common driveability problem we see is a check engine lamp with or without a customer complaint. To get your diagnosis underway, attach the scanner and make note of the recovered codes, but don’t be too quick to clear the codes; the next step is to review the freeze-frame data to see what was going on when the code was set. This information will be more helpful with certain codes than others, but it’s a good habit to get into no matter what the code.
First, we’ll look at some problems that have associated driveability complaints, the most common of which are misfire codes. If the misfire is obvious, you may be tempted to get to work and start switching coils and checking wires to diagnose the problem, but before you do, check the codes and see if there’s more information available. If nothing else, the P0300 series of codes will identify the cylinder that’s causing the problem.
There are many other clues that may be available that will help in the diagnostic process. For example, if you have a misfire code along with a system lean code, you should be thinking that the misfire could be a result of a manifold or other vacuum leak. Even with no code, take a look at the data with an eye toward the fuel trim numbers. Do you have a high positive number on a long-term trim indicating the system has been adding fuel? Or, are you experiencing the less common problem of a negative number and a rich condition, where an extreme case like an injector sticking open or a fuel pressure regulator leaking in the vacuum line could have led to the misfire?
Another common driveability problem that may or may not have an associated code is a stumble or cutting out on throttle tip-in. If the check engine light is illuminated, hook up the scanner and retrieve the code, the most common of which will be a system lean code. While you have the scanner installed, take a couple of minutes to look at the other available parameters. Are the temp sensors reading correctly? With a cold engine, the coolant and air temps should be close. Take a look at the throttle position switch, paying particular attention to the off-idle area. There have been some reports of problems with the switches that become apparent when the connector is wiggled.
Don’t overlook mechanical concerns and be sure to check the air intake hoses for cracks that will open up when the engine moves with torque.
In the case of no-start problems, it pays to know the service history. If the car has suffered a broken timing belt, it’s a good possibility that some debris from the broken belt has found its way to the crank sensor, damaging both the sensor and trigger wheel. On the 2.4L engines, the balance shaft belts have been known to fail and go unnoticed until the pieces finally take out the crank sensor, resulting in a poor run or no-start issue.
ELANTRA CASE STUDY
We recently had a 2002 Elantra GLS in the shop with assorted problems, so let’s take a look at this job since it’s a good example of some common problems we see. The car wasn’t in great shape, and a persistent check engine light was preventing it from passing the state inspection.
As is often the case with this kind of job, the customer was reluctant to make a big investment, but also wasn’t in the position to buy a new car. The obvious problem was a code for a solid misfire in the No. 3 cylinder (P0303), as well as codes for a slow response from the front O2 sensor (P0133), a system lean code, plus there was a slight, but audible, exhaust leak at the flex pipe before the cat. The customer had already installed a new O2 sensor, but the code persisted.
Even though we explained to the customer that there was no way we could give a firm price on the job, we received authorization to get started with the diagnosis and to get further authorizations as the job progressed.
The first step was to deal with the misfire since we also had the system lean code. We knew the problem was with the No. 3 cylinder, so we went right to the manifold in that area. A quick shot of intake cleaner at the manifold flange smoothed the engine out, letting us know we were on the right track.
We used a stethoscope where the sound of the leak is obvious in order to confirm and pinpoint the problem. Knowing that there was little cushion in this job, we checked compression as well as the ignition components when the gasket was replaced. When we were sure the misfire would be repaired and the car would certainly run better with the manifold gasket, we received 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 the output of the rear O2 sensor and it looked to be operating as expected in spite of the exhaust leak.
While we were aware that fresh air entering the exhaust system could lead to an O2 code, with our budget constraints in mind, 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 necessary additional repairs.
Our experience with Hyundais has taught us that they 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 been 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’re looking for a starting coolant temp below 104º F with a gain to 120º F before the test will 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 a service information system. The ECUs know nothing about being close enough; if it’s looking for 104º F, then 105º F won’t cut it and the test will not be run (and some tests will look for an even higher temp). 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.
While the Elantra ran well, it took only a couple of drives before we had the O2 code back. When we monitored the front O2 signal, it appeared to be switching well, but it 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 sensor looked better, and it took awhile, but the code eventually still set. At this point, we’re back to looking into our service info and checking for issues on iATN (www.iATN.net, the International Automotive Technicians Network), something that should have been among our first steps.
A quick search on iATN covered the things we already did, but 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. But I can say 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.
A lot has changed since 2002, to the point that on the more current Hyundais you’ll find direct injection (GDI); drive-by-wire throttles; timing chains rather than belts on some engines; and idle stop and go (ISG) technology on the latest models.
By now, we should all be aware of direct injection and how it works. Simply speaking, this system injects the fuel directly into the cylinder rather than before the intake valves in the port. Injecting the fuel into the cylinder takes advantage of the cooling effect of the fuel, resulting in a more dense mixture that permits the use of a higher compression ratio, providing increased horsepower and torque.
More torque results in the same acceleration with less throttle opening, which increases the miles per gallon. Efficiency is also improved with more precise timing of the injector pulse and eliminating the fuel dropout that takes place with port injection.
You need enough fuel pressure to overcome the increasing cylinder pressure to deliver the fuel into the cylinder. Hyundai uses an in-tank, low-pressure pump to deliver 65 psi to a camshaft-driven, mechanical high-pressure pump that will boost the pressure to 580 psi at idle, to a maximum of 1,958 psi at full throttle to ensure fuel delivery as the cylinder pressure increases with rpm. This pressure is controlled by an internal pressure regulator in the pump and monitored by a fuel rail pressure sensor.
In the event of a failure, a limp-home mode is provided where 65 psi will be delivered. This system also uses a new design and operating strategy for the injectors that can handle the increased pressure.
Speaking of fuel pressure, good work habits are more important than ever when dealing with this type of pressure. Always release the pressure before working on the system; it’s easy enough, especially if you check your service information for the model you’re working on. You will have to remove the fuel pump relay and start the car to run down the pressure.
The only downside to GDI seems to be that with no fuel flowing over the intake valves, there have been some reports of carbon buildup on the valves and ports. There are many theories on what causes this carbon buildup, but all seem to substantiate that the oil that passes through the intake manifold from the crankcase ventilation system is a major cause. Some engineers feel the problem starts when fuel contacts the back of the intake valve, resulting in a soot-like substance that encourages the carbon buildup.
As technicians, we should be encouraging our customers to use a top-grade gasoline and periodically add a fuel additive like Techron. The good news is we perform a fair amount of service on Hyundais and haven’t experienced this issue.
Idle stop and go is the latest technology also aimed at increasing efficiency in mileage and emissions. As the name implies, this system turns the vehicle off when it’s stopped when certain criteria is met. It looks at factors like brake pressure, battery condition and vehicle speed to make its decisions. When the vehicle is stopped at a traffic light, the engine is turned off until the brake is released, at which point the engine will restart. An electric oil pump is equipped to maintain the necessary pressure in automatic transmission-equipped cars to allow the transmission to respond without lag.
All of this new technology is certainly interesting, and while some of it may create a diagnostic challenge, it makes my job as an import vehicle specialist so rewarding. Embrace the challenge to keep up with the changes, and avail yourselves to the wealth of available information.