Intermittent Starting Issue

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jakobgrayhair
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Joined: Wed Jan 08, 2020 4:33 pm
Location: Oregon

Intermittent Starting Issue

Postby jakobgrayhair » Wed Dec 28, 2022 11:56 am

So, I have 2007 Nissan Pathfinder SE OR with a 144k miles. About a year ago, I drove my daughter to school and on the way back (after about 10 minutes of driving) I had to pull over and turn it off. A couple of minutes later, I try to start it up and it cranks over strongly, but won't start. I try 3 times, and then try to figure out a plan. After about 3 minutes, I tried again and it started up. No issues for the next year until two months ago, when the temp dropped here in Oregon (20s here in the Portland Metro area).

It has now done this same thing several - including just this morning - Will crank strongly, but doesn't start, and so I wait a minute and it fires up.

I do feel like the engine is cranking over a little longer than it use to, but I'm not sure.

The only new code I am getting, using a Blue Driver code reader, is P1615 "New key, or key unmatched". I have the original key, so I don't know what is going on there. Does a key issue allow the engine to crank, but not start?

Thanks for any help!


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VStar650CL
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Re: Intermittent Starting Issue

Postby VStar650CL » Wed Dec 28, 2022 1:39 pm

See if the security lamp is lit solid when it does this. If so, it could be that your key is getting weak in its old age, or it could be a malfunctioning ECM Relay. If the sec lamp isn't lit then the P1615 is incidental or possibly "past" and isn't causing the problem. The list of things that can cause a no-start without codes is pretty short, fuel delivery or pressure, crank sensor, cam sensors, MAF, exhaust blockage.

jakobgrayhair
Posts: 5
Joined: Wed Jan 08, 2020 4:33 pm
Location: Oregon

Re: Intermittent Starting Issue

Postby jakobgrayhair » Wed Dec 28, 2022 3:00 pm

Thanks for the response! Well, the security lamp is not lit.

So, how would a very amateur mechanic (i.e., me, a guy who is learning to work on cars by waiting for issues to arise and checking forums and Google) go about checking for these things? Just google each of those problems? Or should I take it to a mechanic to diagnose? Things I could do to narrow it down?

Again, thanks for any help!

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VStar650CL
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Re: Intermittent Starting Issue

Postby VStar650CL » Wed Dec 28, 2022 5:02 pm

This all assumes you've already popped a coil and a plug to make sure you have spark and that the plugs aren't soaking wet. Nothing Nissan will start when flooded, and of course you need good spark. On Nissans the ignition timing is determined by the crank sensor (CKP), so if the coils have power but there's no spark, immediately suspect a bad CKP.

Checking for a fuel starvation issue is easy, pop the airbox and spray something combustible like Brakleen or Gumout down the barrel. If it starts and stalls then it's fuel starved, if it starts and stays running then it probably has low fuel pressure (most likely a balky pump). If it doesn't start then you've excluded fuel starvation as the cause. The fuel systems on Nissan VQ's with port injection are dirt-simple, the check valve and filter are both built into the pump, so there's really nothing besides a bad pump which can cause low pressure.

The MAF is hard to check without a scanner that can stream data, but I'm pretty sure your Blue Driver will do that. The rule of thumb is that you should see a bit more than the engine's displacement in grams per second at idle, so a VQ40 should read something around 5 GpS at idle and about 1.5 GpS when cranking. Some scanners give pounds per minute instead of GpS, to convert it multiply by 7.5. The reading should be reasonably steady and go up predictably when you tap the gas. When MAF's go bad, the most typical symptom is inconsistency.

Nissan VQ engines have a useful trait that you can use to check the CKP and cam (CMP) sensors. First, understand that a no-codes no-start occurs when one of the sensors is lying but not dead. Dead sensors will give you codes. On VQ's, if the CKP is good but both CMP's are dead, it will start on the CKP alone after a long crank. If both CMP's are good but the CKP is dead, it's the same thing. So you can exclude the CKP by disconnecting both CMP's and see if it starts. If it does, the CKP is vindicated and one of the CMP's is implicated. If it doesn't start, reconnect the CMP's and disconnect the CKP. If that starts it then the CKP is bad, if it still won't start then the problem is elsewhere.

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VStar650CL
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Re: Intermittent Starting Issue

Postby VStar650CL » Wed Dec 28, 2022 5:10 pm

PS - Nico has complete factory manuals for almost every USDM Nissan from the late 80's to 2016. Here's the link to the Engine Controls section for your ride:
https://www.nicoclub.com/service-manual ... 7%2Fec.pdf

jakobgrayhair
Posts: 5
Joined: Wed Jan 08, 2020 4:33 pm
Location: Oregon

Re: Intermittent Starting Issue

Postby jakobgrayhair » Wed Dec 28, 2022 6:04 pm

Thank you!

I replaced the plugs in July, and everything seemed good then. And the issue happened once last year.

It seems to be increasing in frequency, but it still starts eventually, after letting it sit for anywhere from 30 seconds to 5 minutes after I first tried to start.

I did have a camshaft sensor go bad 2.5 years ago (can't remember which side) and when it did the VDC and Slip lights came on. I had an issue with the lights coming on again this summer, so given what you said, I will try checking out those camshaft sensors first.

Thank you again for all the info!

TooMuchControl
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Re: Intermittent Starting Issue

Postby TooMuchControl » Thu Dec 29, 2022 5:13 pm

I had an old Dodge Spirit, and it did the same exact thing. Gradually would start after the pause.
It was a fuel line issue - pump pressure or filter. It was worse when it was warmer.

The smell of gas - or perhaps more precisely, the lack of smell of gas, hints fuel pressure is low.

Next time you have the issue:


Key the ignition to ON/Accessory position, but do not START.
Do this maybe 3-4 times.

This action should prime the fuel pump, and build fuel pressure in the lines.
On the 4th time, key to START, see if it starts up.

If it does....


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