Misfiring at idle
11-07-2018, 12:47 PM
#16
has the car sat for extended period of time?
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.
11-08-2018, 05:28 PM
#19
bad gas can lead to the destruction of the fuel pump. Also keep in mind that gas does not go away if the car sits meaning it sits inside the injectors, fuel filter, fuel pump, lines and since gas is oil based eventually turns into gunk which can cause ur injectors to be leaky or slow the speed of the fuel pump. Defently sounds fuel related to me. how is the car in cold start? If you start it cold and drive it cold does it run worse then normal?
12-08-2018, 02:55 PM
#20
I took the car to yet another mechanic who is also having trouble fixing it. He will most likely give up and return the car with the misfire. This thing is undiagnosable; I didn’t know that could even happen. The stock intakes are back on and the car will be sold or traded in the upcoming week. Thank you for all of your input and suggestions!
12-08-2018, 03:11 PM
#21
Out of curiosity, was there any oil inside of the banks of the plugs? if you have a leaking valve cover gasket, then oil could be seeping into those banks and fouling the plugs. At 160k miles it could be a possibility. I'm experiencing the issue now at 80k
12-08-2018, 07:50 PM
#23
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Same thing happened to me with my old Maxima. Leaking VC gasket led to oil pooling in one of the plugs, which eventually led to an intermittently failing coil-pack. Replaced the gasket, cleaned out the plug hole, replaced the CP... oddly enough, the spark plug was A-OK.
12-12-2018, 02:17 PM
#29
has the car sat for extended period of time?
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.
if the intake swap to stock didnt help i would start with the basic. At this point you need to try anything you can. Assuming the stock intakes are back on i would do a spark test make sure spark plugs are clean and no injectors are leaky, coils are good etc, also check fuel pressure for fuel pump, see if injectors all click, gas is good.
Ive had an issue like this it ended up being the fuel pump but the dealer picked it up on they're scanner.
The one sensor it could be is the maf or map since it picks up manifold pressure and tells the computer what mixture to send out.
My Audi also had a leaking valve cover gasket that fouled out the plugs and caused serious misfire.
A stuck open injector can flood and cause a misfire also, and has done so on some vehicles. On the flip side a clogged injector can starve the cylinder at idle but provide enough fuel at WOT to not register a misfire. It can be cleaned and tested but fuel injectors start at $35 and I would just replace it.... on the BAD cylinder in question.
No freak'in way. I can tell you over the 7 years difference between those two cars that there has been dozens of minute changes that we will never see. What are those changes? I don't know, but I work in engineering, and if I can tell you anything its that engineers never leave anything alone. They are constantly tweaking.
Last edited by Rochester; 12-12-2018 at 03:16 PM. Reason: Removed pre-flame content, you know... for the kids.
12-12-2018, 03:01 PM
#30
Except it didn't change....the only change in a decade was a gasket in '12.
https://en.wikipedia.org/wiki/Nissan_VQ_engine#VQ37VHR
The stagnant powertrain was a gripe until the new 3.0tt replaced the 3.7. Typically, I'd agree with you, especially if this was a German car but it's the same motor.
I'd recommend taking a peak into your banks quickly before buying a new motor OP....A shop will have that completed in 3-4 hours and the gasket is $25 bucks. $450 repair vs $$$ motor + install.
https://en.wikipedia.org/wiki/Nissan_VQ_engine#VQ37VHR
The stagnant powertrain was a gripe until the new 3.0tt replaced the 3.7. Typically, I'd agree with you, especially if this was a German car but it's the same motor.
I'd recommend taking a peak into your banks quickly before buying a new motor OP....A shop will have that completed in 3-4 hours and the gasket is $25 bucks. $450 repair vs $$$ motor + install.
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