Welcome back to the Auto Specialist. Over the past several months, I’ve been answering readers’ questions about the car problems they’re experiencing. During that time, we’ve addressed issues related to engines, transmissions, alternators, and nearly every other component under the hood. The purpose of doing so is to demystify your vehicle. That way, you’ll know what your mechanic is saying as he recommends solutions. Even better, you might be encouraged to perform a few minor repairs and replace parts on your own. Doing so may be simpler than you think.
In the last segment, we helped Todd figure out a problem with his Infinity’s timing belt. We also helped Erin understand what the white material on her Accord’s battery was. Today, I’ll answer a question from Allen regarding his Concorde’s misfire and explain a leakdown test to Marla. Let’s jump right in.
Question: I own a 1999 Chrysler Concorde with 136,000 miles. For the past couple of months, my car has been misfiring. It happens sporadically and I’m not sure what’s causing it. When it first started occurring, it was only during acceleration on the highway. But, now it happens in different circumstances. Any idea what the problem is?
Answer: Thank you for your question, Allen. Misfires can happen for a lot of different reasons. One of the most common is a vacuum leak. Besides a misfire, you might also notice rough idling, stalling, and hesitation. You can check for leaks by using a bottle of propane gas and a rubber hose. Attach the hose to the gas valve and while keeping the valve open, place the other end near areas where you think there may be a leak. You’ll see the propane being siphoned in.
Aside from a vacuum leak, the misfire might be due to bad spark plugs, a failing EGR valve, a malfunctioning ignition coil, and even clogged fuel injectors. My suggestion? Have your mechanic run diagnostic and compression tests.
Question: I’m driving a 2002 Honda Odyssey and the odometer is at 81,250. Last week, I took my van into the dealership for a routine check-up. The technician said that I should have a leakdown test done. He tried to explain what it was, but I feel clueless. What is a leakdown test and why it is done?
Answer: Thanks for taking the time to write in, Marla. Here’s a brief explanation. Your engine has cylinders. Each cylinder has a piston that compresses air and fuel within a combustion chamber. A spark plug ignites the compressed mix, which generates the energy needed for propulsion. A leakdown test measures how much pressure loss there is from a given cylinder. If the loss of pressure is over 30%, that means your engine is not operating properly. Hope that clarifies what the mechanic was trying to explain.
That wraps up today’s segment. I’d like to thank both Allen and Marla for taking the time to send in their questions. If you’re experiencing a problem with your vehicle and your mechanic isn’t providing adequate answers, feel free to send your questions in. In the next installment, we’ll answer Brad’s question about his Lancer’s oxygen sensor and help Jason figure out what’s wrong with his Aurora’s brake pads and rotors. Until next time, drive safely.