---- — Q: I have a 2000 Nissan Frontier truck. It has 40,000 miles, and I have been the only owner. It misfires randomly. It has stalled once at a stop sign. There are no check engine lights on.
I took it to my local mechanic to get it repaired. They told me that there are no computer codes or other indications shown. They checked the vacuum, fuel injectors and did a complete tune up. They checked and cleaned the injectors and replaced the upper seals that were showing signs of deterioration. The mass air flow sensor was checked. (The unit was replaced, and when no improvement was noted, the original unit was put back in.) They called and consulted with other mechanics, to no avail. They gave up and suggested I take it to a Nissan dealer. I did. Nissan had it for three days. They consulted with Nissan national service. They also gave up.
The service manager said that in his entire career, this was only the third car they could not diagnose and fix. They suggested I drive it until whatever is wrong completely fails and they get a solid computer code. I am not comfortable with this.
All who have looked at this truck verify that it misfires (5 seconds). They cannot find out why. They all seem lost because the computer is not telling them anything. I did get a check engine light once, but that only indicated that the engine was misfiring. No solid code to indicate why. Do you have any suggestions?
A: The issue here is that the problem is not consistent. I am happy to see people are not throwing parts at the truck until they happen upon the right part. A few ways to isolate the problem would be to drive the truck with a flight recorder attached. When the misfire occurs, you would press the record button.
The flight recorder, which most of your better shops have, is always monitoring your engine system and keeping around 20 seconds or more, prior to the button being pressed in memory. Once the diagnostician gets his or her flight recorder back, they will be able to download and isolate the misfiring cylinder.
Now the fun begins. Sources of misfire can be fuel, spark, compression or timing. It is going to be a very interesting problem, but a very expensive problem to diagnose.
Car Care Tip: An overheating engine needs immediate attention. Once that needle goes past three-fourths, it’s time to shut it down. You can try turning on your heater to full heat and full fan as an emergency measure to bring the engine temperature down.
Larry Rubenstein is a master technician who owns a North Shore service station. His column appears most Tuesdays. Write to Larry at the Gloucester Daily Times, c/o Auto Scanner, 36 Whittemore St., Gloucester, MA 01930, or send an email to email@example.com.