Find a patient technician to track down problem

Dear Mr. Green: I bought my 1998 Buick Regal V-6 (101,865 kilometres) new and have it serviced by the dealer regularly.

At 93,119 km, the engine was sluggish and the dealer performed a minor emission service. There was noticeable improvement.

At 99,518 km the service engine light came on, and remained on. The dealer performed a scan check, installed a new fuel tank cap and reset the light. Now, there is a new problem that I suspect will be difficult to isolate, as it occurs only occasionally at a speed of approximately 80 km/h. There is a momentary engine hesitation, as if one cylinder is misfiring, and then it goes away and may not happen again for several days. I have no idea what could be causing this.

I would appreciate your thoughts on this problem and

what might be causing it.

— Mr. Fire

Answer: Short-trip, stop-start driving has the effect of shortening engine oil and sparkplug life. In this situation, the engine often will not get up to operating temperature and stay in the range. Given the year of your car, and the kilometres on the clock, this statement could describe your driving pattern.

I know this engine is equipped with long-life spark plugs, but a new set of spark plugs and spark plug wires would be one of my first steps. Yes, this problem will be tough to track down, and you may wish to leave the car with the mechanic for a few days.

Ask to have it driven to and from the shop. This strategy will only work if the tech’s drive includes a stretch of road with a speed limit of 80 km/h or more. I have driven customer vehicles over a period of days on several occasions to verify a drivability complaint.

This power-train has proven to be reliable over the years, but the symptoms could point to a transmission-shifting or torque converter clutch lock-up situation. A transmission fluid change may smarten it up.

But again, the first step in the process is to get a patient technician to verify the condition.

Dear Mr. Green: I bought a 2006 Expedition in 2007 without adequately reviewing complaints registered against that model.

There have been nine related to engine shut-off at highway speeds. In some cases, the engine restarted; in some cases it did not. The average kilometre reading for these events was 106,554. I have been living in fear of such an event occurring to my Expedition.

Is there any possibility that the Innova CAN OBD II Scan tool would be able to foresee such an event?

— Looking into the Future

Answer: A modern, on-board diagnostic system is quite complex. Associated with any diagnostic trouble code is a diagnostic routine. The vehicle must be op- erated under specific conditions for the diagnostics to run. Some diagnostics are one trip, others take two.

If the result is a failure (the diagnostic runs and the results are out of parameter), either the engine light will come on immediately, or a pending code is set. The engine light does not come on for pending codes.

As far as being able to foresee a failure, there might be a clue if a pending code was stored. This strategy is a long shot, and I wouldn’t buy the tool just to look for pending codes.

If the possibility of getting stranded concerns you, consider taking the truck to a dealer. There, the scan tools, bulletins and tech line help will all be Ford-specific, and I would take the time to seek out a long-term driveability technician. Chances are good the problems are known, and a seasoned Ford tech will have the answers. If there are documented stall or no-start issues, there must also be fixes for these problems.

I would not go into the dealership with a massive stack of postings from various forums on the Internet.