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Discussion Starter · #1 ·
Been scratching my head over this for quite some time. 2004 Maxima SE (5 speed AT) will turn over and fire up when cold (sitting 30 minutes or so), and immediately after cutting off (no matter what distance is driven), but after 15-30 seconds, it gets progressively harder and harder to start, up until the point it is cold. Behavior is very repeatable.

To back up, some history. Wife was driving it and said the car cut off and wouldn't go above 2000 rpm and the MIL light was on after restarting. The P0340 code, I later learned, threw it in limp mode, and the "2000 rpm" limit was the fact the trans locked in 5th gear. Replaced the VIAS thinking it might have been that. Bought both front and rear sensors just in case, tossed them in the trunk, and drove the car for several months with no issue. Was driving this past weekend and had the same thing happen. Replaced the front camshaft position sensor since it was in the trunk, cleared the code, and was on my way. A few miles later, it cut off again, and restarted back into limp mode. Drove it to a house and replaced the rear position sensor.

Car drove back home just fine (several hundred miles without me stopping), but then had an issue where the car wouldn't start back after sitting for a few minutes (less than 5). Tried resetting security/pulling the negative, and that only worked after letting it sit for quite some time. Replaced the coolant temp switch to the ECU with an aftermarket one, but the probe diameter was ~1mm larger, enough to block coolant flow. Regardless, still had the same issue with the new sensor, so the original was reinstalled.

Drove it to work today in the morning, and fired up just fine at the end of the day. Stopped for about 10 minutes and it wouldn't fire up at all. Got some starter fluid, sprayed the intake, and it finally roared to life. Got back to my house again and observed the same repeatable behavior with it getting harder to start when warm up until the point it cools off.

Seems like a fuel issue, but I'm not sure what. The car runs fine for hours of driving after it starts, completely smooth with no skipping, not very indicative of a dying fuel pump. My old Jeep had a problem with fuel drainback that made it hard to start, so I'm thinking it may be that, or something related to that and fuel line temperature (or a combination of the both). Any help would be appreciated.
 

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First thing to try is a new crank sensor. Sensors that are missing occasional teeth or have low sensitivity when the reluctor is moving slowly (i.e., when cranking) can cause all sorts of weird and intermittent problems, often temperature-related and often without throwing any codes. If a new CKP doesn't help, then I'd start looking at fuel pressure or a spotty MAF.
 

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Discussion Starter · #3 ·
I'm confused about the crank sensor. I've already replaced two sensors (one angled flat blade style at the front right, another on the rear bank with a flat barrel shape). Are both of these cam sensors? They were accessible from the top of the engine. Is there a third for the crankshaft?
I've already tried a new fuel pump since I was led to believe I'd replaced the cam/crank sensors already. Will try the MAF next, but any clarification on the crank sensor would be a great help (and thank you for the tips).
 

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Yep, there will be two cams (one each bank) and one crank sensor. Don't recall exactly where the crank sensor was located on the older VQ's, but it should be near or on the joint between the engine and bellhousing. Maybe Smj can help us out.
 

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Yep, there will be two cams (one each bank) and one crank sensor. Don't recall exactly where the crank sensor was located on the older VQ's, but it should be near or on the joint between the engine and bellhousing. Maybe Smj can help us out.
The crank sensor should be located on the rear of the oil pan or the block on the left side of the engine. If the car is jacked up in the front, it'll be easier to see/replace the sensor.
 

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Discussion Starter · #7 ·
Thanks for the help. Still lost. Replaced the engine coolant temp sensor and I can let it run for an hour and it starts back no problem. But when I drive it, it behaves the same (no crank until cool). Guess my only option is the crank sensor. Doesn't make a lot of sense as to why driving it makes the difference.
 

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It's adjacent to the tranny and torque converter, which don't get very warm unless you're driving. If you want to experiment, try doing a 1500 RPM torque converter stall for 3~4 minutes to get the fluid good and hot, then see if it duplicates your problem.
 

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Discussion Starter · #9 ·
Went ahead and replaced the crank sensor (for future reference, Nissan lists this part as a "crank angle sensor"), but I'm still having the same problem. It seems that the problem is less and less as I replace components, but temperatures have also been steadily decreasing. This makes me wonder if it is fuel vapor related. The next things I've heard are possibly the ignition switch and the fuel dampener.
 

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Went ahead and replaced the crank sensor (for future reference, Nissan lists this part as a "crank angle sensor"), but I'm still having the same problem. It seems that the problem is less and less as I replace components, but temperatures have also been steadily decreasing. This makes me wonder if it is fuel vapor related. The next things I've heard are possibly the ignition switch and the fuel dampener.
When replacing sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic items generally are not reliable, don't last long, and many times are DOA. The sensors are not very expensive; around $75. Inspect the harness connectors at all the sensors for any oxidation or loose connections. Insure that any water resistant connector is in good condition; if the seals have been compromised, then any water intrusion can cause intermittent problems.
 

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Discussion Starter · #11 ·
When replacing sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic items generally are not reliable, don't last long, and many times are DOA. The sensors are not very expensive; around $75. Inspect the harness connectors at all the sensors for any oxidation or loose connections. Insure that any water resistant connector is in good condition; if the seals have been compromised, then any water intrusion can cause intermittent problems.
I did purchase the OEM sensors for this. When I just went to start the car, it had a smell of gas. I replaced the fuel pump months ago and some spilled around where it goes in, but that should be long gone by now. To clarify the issue, the engine acts like it's on the verge of starting, and some of the cylinders are firing, but it never fires enough to start the engine. I've heard this could be the fuel pressure regulator/fuel dampener, but also leaking injectors. Would the best method of checking leaking injectors be to pull them, let the engine prime, and check for one leaking? Would rather not replace all the injectors only to find out the regulator is bad, but it is also difficult to find a replacement regulator.
 

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I did purchase the OEM sensors for this. When I just went to start the car, it had a smell of gas. I replaced the fuel pump months ago and some spilled around where it goes in, but that should be long gone by now. To clarify the issue, the engine acts like it's on the verge of starting, and some of the cylinders are firing, but it never fires enough to start the engine. I've heard this could be the fuel pressure regulator/fuel dampener, but also leaking injectors. Would the best method of checking leaking injectors be to pull them, let the engine prime, and check for one leaking? Would rather not replace all the injectors only to find out the regulator is bad, but it is also difficult to find a replacement regulator.
To perform a fuel pressure test, tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel damper that's on the rail; you'll need a quick connect adapter tool to release the fuel hose. The readings at idle should be around 51 psi. If the pressure is very low, it could be that your new fuel pump is bad or a bad regulator which is inside the fuel tank mounted on the pump.

While you have the temporary fuel pressure gauge still installed, a quick test for leaking fuel injectors is to turn the ignition switch to the run position without starting the engine. The fuel pressure should stay around 51 psi for a long time. If it drops of quickly, that indicates one or more injectors are leaking.

To find a leaking injector(s):
1. Unbolt the fuel rail from the intake manifold and pull off the entire assembly.
2. Keep the fuel hoses still connected and don't remove any individual injectors. The injector harness connectors should remain connected.
3. Unplug the ignition coil wire from the coil or on late model vehicles, disconnect harness connectors from all ignition coil packs .
4. Place pans under each injector.
5. With the assembly now away from the intake, turn the ignition key to the run position WITHOUT STARTING THE ENGINE. Now observe each injector to look for leaks. There should be no drips.
 
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