Q: I recently purchased a 2004 Nissan Sentra with the four-cylinder 1.8 engine and 74,000 original miles. From Day 1 it's had off-and-on hard starting. The dealer finally replaced the crankshaft position sensor, which seemed to help some. Then the starter failed and my mechanic put in a new starter and another crankshaft position sensor. Now I'm back to square one – hard starting. My mechanic found no DTC codes. What do you think the problem is?
A: Fuel pressure. Or more precisely, lack of it. There is no direct fuel pressure sensor in the engine management system. If fuel pressure bleeds down after the engine is shut down, it will take a period of cranking to build up fuel pressure to the required 51 psi to run the engine. No code will be thrown because from the engine control module's point of view there's nothing wrong — it's just "out of gas," so to speak. Once fuel pressure comes up, the engine starts and runs normally as if nothing happened.
Here's a quick DIY test. Locate the fuel feed hose in the engine compartment and pinch it firmly between your gloved fingers. Have a helper turn the key to the "on" position. You should feel fuel pulses in the hose for one second, confirming that pressure is building up quickly.
If you don't, try turning the key on for two seconds, then off, repeating this a half-dozen times. Then try starting the engine. If it fires right up you have identified the issue — lack of fuel pressure.
Have your mechanic "T" in a fuel pressure gauge between the fuel hose and the fuel feed line. Check for leaks and start the engine. Confirm that there's 51 psi fuel pressure at idle. Then shut down the engine and monitor how long the system holds fuel pressure. If it bleeds down very quickly — less than a minute — the problem is most likely in the fuel pump assembly in the fuel tank, which is accessible through an inspection plate under the rear seat. Nissan offers a fuel pump repair kit to fix this problem.
Q: What is your take on the CVT technology being so widely adopted? I like today's multi-speed automatics. I suppose the CVTs are cheaper to produce, but can they possibly be as reliable as automatics? Reminds me of the old Buick Dynaflow Drive. Lots of RPM as the driveline works to catch up to the engine speed. Not so much reliability.
A: I've never liked the "feel" of a continuously variable transmission — except on snowmobiles and ATVs where they are ideal for power transmission by keeping the engine in its most efficient RPM range regardless of speed. The sense of slippage seems magnified in an automobile, perhaps largely due to our lack of familiarity with the feeling. But CVTs do work quite well. Instead of your "multi-speed automatics," CVTs are effectively "constant speed automatics" with infinitely variable gear ratios, each the perfect RPM< and torque for the specific conditions of operation at that moment.
With modern engineering, metallurgy and manufacturing, durability doesn't seem to be a major concern these days. They just feel weird!
Motoring Note: On whether or not to shift to neutral at stops — from Tim McNeely, "one other reason not to shift to neutral at intersections — it is illegal. Some states have it in their driver's manual. I don't like it. I drive a stick and rest my left foot at intersections, especially at long lights."
I'm with you. Granted, holding the clutch down disengages the engine from the driveline like "neutral," but generates wear and tear on the clutch release bearing. For longish stops, I shift a manual transmission into neutral and take my foot off the clutch pedal.
As far as legality, I could only find state statutes that prohibit coasting in neutral downhill, not shifting to neutral while stopped.
Paul Brand is the author of "How to Repair Your Car" and "How to Repair Your Truck and SUV," published by Motorbooks.