Hard starting when hot

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7,847
Location
Hudson, NH
2006 Nissan Altima 2.5 S. 166k. Starts great when its cold. Hard starts when its warm or hot after sitting 15-20 minutes. For example I start the car in the morning. Drive to the grocery store. When I come out 20 mins, 1/2 hour later it doesn't want to start. Cranks for a good 15-20 seconds then starts. No codes. Battery, alternator, starter are ok. Replaced crank sensor, cam shaft sensor with OEM. Recently replaced the water pump, both thermostats, temp sensor, all the coolant. Not going through any coolant or oil since I started driving it 300 miles ago. Just seems like when the engine warms ups, doesn't want to start and I may get stranded. I'm not sure what to do next, would appreciate any help.
 

JHZR2

Staff member
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45,318
Location
New Jersey
Have you tried giving some throttle when cranking?

My old bmw 318 had an issue like this, and it turned out needing a new fuel pump and a check valve on one of the lines. I suspect it was related to insufficient prime on the older/weaker pump, combined with the ecu not pushing as much fuel since it is hot.
 
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2,836
Location
DELAWARE
Hope you get it sorted. I have a 2009 Ford Ranger with the exact problem. Cold engine, it fired right up but on a warm engine that sat for a few minute like if you went in grocery shopping and came back and still semi-warm, it was an extend crank like 5 seconds or so before it started again. No codes and fuel pressured checked good. Shotgunned a couple of parts like a temp sensor and IAC but just lived with it for a couple of years before trading it.

I think you are going to need a good diagnostic tech and some time to get it figure out.
 
Messages
1,679
Location
RI
How long ago did you change the cam/crank sensors? They are the most common culprit for this on these engines. I’ve seen bad ones out of the box, too, from Nissan.

Your best bet is going to be putting a scanner on it when it won’t start looking at data.

If you just push slightly on the throttle does it make a difference?
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
How long ago did you change the cam/crank sensors? They are the most common culprit for this on these engines. I’ve seen bad ones out of the box, too, from Nissan.

Your best bet is going to be putting a scanner on it when it won’t start looking at data.

If you just push slightly on the throttle does it make a difference?
Both installed Saturday. I can start by ordering a couple more off RockAuto the OEM is Hitachi?
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
Have you tried giving some throttle when cranking?

My old bmw 318 had an issue like this, and it turned out needing a new fuel pump and a check valve on one of the lines. I suspect it was related to insufficient prime on the older/weaker pump, combined with the ecu not pushing as much fuel since it is hot.
I have not tried throttle. Will do that.
 
Messages
1,976
Location
Minnesota
When it doesn't start go sniff back by the tail pipe. See if it is flooding. If so...diagnose from there. And STOP the shotgun...replace parts approach. It will bankrupt you.
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
How would I rule out the camshaft or crankshaft position sensor by testing? How would I test it? It's 3 wire. I have voltage ground and something else. If it were the crankshaft sensor what am I momentarily missing fuel? Spark? When I turn the key on just before trying to start I hear an electrical noise I'm not sure if that's the throttle plates or the pump priming.
 
Messages
1,679
Location
RI
How would I rule out the camshaft or crankshaft position sensor by testing? How would I test it? It's 3 wire. I have voltage ground and something else. If it were the crankshaft sensor what am I momentarily missing fuel? Spark? When I turn the key on just before trying to start I hear an electrical noise I'm not sure if that's the throttle plates or the pump priming.

Easiest way to verify cam/crank signal and sync is with a scanner. It’s probably the pump priming what you’re hearing
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
The reason why I'm asking about the crankshaft sensor test is because there was a recall for the 2.5 Nissan engine years 2002-2006. Because of its position between the engine block and the bellhousing the crankshaft sensor can overheat causing a momentary loss of signal to the PCM. So there's a potential the car could stall during operation. That hasn't happened since I started driving the car the past week but symptoms of a bad crankshaft sensor are present. Like when it's warm or hot it gets hard to start. The idle gets rough. I know that could be other things but because of the recall I would like to rule crankshaft sensor out first.
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
Easiest way to verify cam/crank signal and sync is with a scanner. It’s probably the pump priming what you’re hearing
I don't have a scanner just a code reader with live data . Is there a way to test the ohms and voltage of the circuit with a multimeter? It's a three-way wire so I'm figuring it's 12 volts. A ground. And a signal wire.
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
Check your fuel pressure regulator if the engine has one. Take off the vacuum line and give it a whiff. If it smells like gas, then your fuel pressure regulator is bad and passing gas through the line.
In the past week I have not been able to get the EVAP monitor ready. I attributed that to resetting codes and changing the sensors. And not driving the car enough. But it is taking a while it's been over 100 miles and the EVAP monitor is still not ready everything else is no codes
 
Messages
1,175
In the past week I have not been able to get the EVAP monitor ready. I attributed that to resetting codes and changing the sensors. And not driving the car enough. But it is taking a while it's been over 100 miles and the EVAP monitor is still not ready everything else is no codes

I’ve had evap monitors take hundreds of miles and weeks worth of driving to become ready again. They have very specific driving patterns that must be met.
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
Looks like one or more fuel injectors leak after shutdown flooding the engine. If it starts easier with the accelerator fully depressed when warm then you should have found the solution to the problem
I tried that and it was still hard to start after sitting for a half hour after use. Will try it again to be doubly sure it was fully depressed.
 

LeakySeals

Thread starter
Messages
7,847
Location
Hudson, NH
I’ve had evap monitors take hundreds of miles and weeks worth of driving to become ready again. They have very specific driving patterns that must be met.
I drove it today and it's still not ready. I wonder if maybe something's wrong and I'm not getting a code because the monitor is not ready? Like maybe a faulty purge valve is why the engine is so hard to start warm. I should get a code rather than just a monitor not ready forever?
 
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