Hesitation May Be Due to Wet Computer
Question: My 1998 Nissan Altima hesitates and sometimes is difficult to start. I have an independent mechanic who looked over the car. On the day he checked it, the problem was not occurring. He said he performed a complete fuel and ignition system check. I’m baffled and not sure what I should do.
--S.K.
Answer: A drivability problem like what you describe can be caused by many things, both in the electrical system and in the fuel system. Your car’s on-board diagnostic system should be recording error codes that could help in figuring out what’s going wrong.
One possibility that Nissan has identified involves water that can leak into the car’s main electronic control module. The company has issued a technical service bulletin, reported by automotive publisher Alldata, warning of a problem similar to what you describe.
The problem begins with debris blowing into the car’s ventilation ducts and contaminating the air-conditioning evaporator equipment under the dashboard. The evaporator is what produces cold air, and it also generates a substantial amount of condensation, just as any air conditioner does.
The system has a drip pan and a drain tube to remove the water and dump it under the car. That’s why you often see water puddles under a parked vehicle after its air conditioner has been running.
The service bulletin warns that debris can plug the drain tube and allow water to spill onto the electronic control module, which is the engine’s central computer for controlling many functions. Wet computers are really bad news.
Such blocked tubes normally spill out quite a bit of water, so if a blocked drain tube is your problem, you’ll probably find that your carpeting also is wet.
Nissan advises mechanics to clean out the debris and dry off the carpeting. A new module also may be needed.
Shifting Problem Could Be Sign of Dirty Fluid
Q: My 1998 Volvo S70 seems to be shifting harshly, more so than in the past. It has 62,000 miles on it. I don’t know if the transmission is failing or what, but my regular mechanic said he didn’t think it was anything serious. Can you please advise?
--G.S.
A: The problem could be as simple as dirty automatic transmission fluid, which can cause hard shifting, particularly when the transmission locks up in certain gears.
The fluid is supposed to be red or reddish brown. If it is pink or cloudy, that probably means it has become contaminated with engine coolant. If that’s the case, then the job will get more expensive.
Engine coolant typically leaks into the transmission fluid at the radiator, which provides cooling for both the transmission fluid and the engine coolant. Volvo advises replacing the radiator, the transmission oil cooler and the connecting hoses.
The job also requires that the transmission be flushed numerous times to purge any residual engine coolant. The cost is going to be shocking. The radiator retails for about $550, though the part is available at discount for a few hundred dollars less. There is a substantial amount of labor, so hold on to your wallet.
Puzzling Over Pair of Unmatched Tires
Q: After recently purchasing two tires for my Nissan Pathfinder, I discovered that their circumference differs by 1.5 inches. How could this happen, and is it a problem?
--W.T.
A: The situation is unusual, though it also seems unusual for a person to check the circumference of tires. I admire the attention to detail.
Assuming the tires are the same model and brand and have the same air pressure, it appears a manufacturing defect was involved.
The difference in circumference is enough to raise safety concerns regarding braking, traction and transmission wear. You could try to fiddle with the air pressure to obtain a uniform circumference, but that is fraught with safety issues also. I suggest you return the tires to the dealer and ask for a different brand under a warranty replacement.
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Ralph Vartabedian cannot answer mail personally but responds in this column to automotive questions of general interest. Please do not telephone. Write to Your Wheels, Business Section, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012. E-mail: ralph [email protected].
