A There are many possibilities, but start with the basics: old or fouled spark plugs, inaccurate coolant temperature or manifold absolute pressure (MAP) sensor, sticky throttle position sensor, leaking fuel pressure regulator/fuel injector or low battery/system voltage.
Three professional tools may help pinpoint the problem. A scan tool connected during start-up lets a technician monitor signals from the engine sensors in real time to determine whether the signal values are accurate. A fuel pressure gauge can easily identify low fuel pressure or a leaking fuel pressure regulator -- any liquid fuel in the vacuum hose to the regulator would also confirm this. Finally, try connecting the engine to a professional electronic engine analyzer to monitor ignition and combustion with the engine operating from start-up through the sputtering.
Q We have a 2002 Camry with 115,000 miles on it. On Sept. 22, the engine light went on. We checked that the gas cap was on tightly. The dealer did a computerized evaluation, replaced a vacuum valve and manually turned the engine light off. We paid $214 for this. On Oct. 4, the engine light came on again. This time, the dealer replaced a canister assembly for another $515. On Oct. 17, the engine light came on again. The dealer said they couldn't do a smoke test because the gas tank was too full. They told me to bring it back when it was less than a quarter full.
We pointed out that since neither the first nor the second attempted repair managed to fix the problem we should get our $729 back. No dice. Again, they manually turned off the engine light, and we drove the car until the gas tank was below one-quarter. The light had not come back on by then, so I didn't take it in. We filled the gas tank and continued to drive it. On Nov. 15, the engine light came on for the fourth time.
Have we been taken for a ride?
A Only if the dealer didn't really give it his best effort to find the problem. If they just threw parts at the car based on diagnostic fault codes, you have a valid point. But then again, do physicians refund money for a misdiagnosis?
Although you didn't share the specific fault codes the dealer found, I'm assuming they relate to the evaporative emissions system. A vacuum leak -- which they may find with the smoke test -- may well be the problem, so why not give the dealer one more try at solving it? If they're successful, negotiate the total cost of all their repair efforts.
Q Our 2007 Mitsubishi Endeavor was totaled in a crash. I loved my Endeavor and want to buy another one. If you were given the choice of a 2008 with 35,000 miles for $14,600 or a 2010 with 26,000 miles for around $16,000, everything else being equal, which would you opt for and why?
A I'd go with the newer vehicle with 9,000 fewer miles for $1,400 more. A quick look at the National Automobile Dealers Association (NADA) used-car pricing guide shows about a $3,500 difference in value between the two vehicles and a retail price of almost $20,000 for the 2010 base model with 26,000 miles.