# 2007 Sentra 2.0 Hard to start!!



## mustang1226 (Sep 10, 2018)

I have a 2007 nissan Sentra with the 2.0 and lately its been hard to start if it sits for over 8 hrs or the first start of the day. It will fire up but the idle hunts up and down and dies. If you start again and it does the same thing but by the third try or so it will clear out and idle and run normal. Any start up after this it starts and runs normal. I have had the p0340, code, P0113, code, p0420 code and p0507 code So far I have replaced the fuel pump, cam position sensor, and crank position sensor with Nissan oem ones. The air intake tube had a small tear in the bottom so I have replaced that as well. Since those parts the only code it seems to be throwing is the P0420 catalyst system Efficiency below threshold bank 1. I am replacing the maf meter today with a oem one. I am really at a loss here. I am hoping someone on here has some insight to this problem. Thanks!!!


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## Lsal2016 (Apr 29, 2020)

Did you ever figure it out because everything you said I did too!?


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## Nissan0301 (11 mo ago)

It would be helpful if people reported back with the issue weather it was resolved or not..


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## VStar650CL (Nov 12, 2020)

P0420 is a "dead cat" code, it means the ECM doesn't see anything wrong with the rear O2 but there's too much oxygen in the outflow, indicating a dying front catalyst. I'm sure he ended up replacing it. Or blowing up the engine. The MR20DE is Miller-cycle, so driving it around until the cat fails is a bad idea. If it clogs then you lucked out, if it melts then the engine will inhale the debris and you can kiss it goodbye.


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## Nissan0301 (11 mo ago)

I only get P0420 when I run random brand gasoline. I was going to look into replacing the front cat, which is combined with the exhaust
Manifold, right?

I don't have a live data scanner yet but I'm definitely interested in the o2 voltage if it shows it. I don't think mine has been replaced in 11 years..


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## VStar650CL (Nov 12, 2020)

Nissan0301 said:


> I was going to look into replacing the front cat, which is combined with the exhaust
> Manifold, right?


No, on an MR20 the manifold is separate and the front and rear cats are combined into one assembly. They're still not too pricey if your car is Fed spec, under $300 on RockAuto. If it's Cali spec then you're in trouble, the CARB-compliant versions are 3x the price and more.



Nissan0301 said:


> I don't have a live data scanner yet but I'm definitely interested in the o2 voltage if it shows it. I don't think mine has been replaced in 11 years..


Get an ELM327 adaptor for your diag port. If you have a Samsung or LG phone, for $5 you can download Torque Pro and it's very capable, lots of live data and work support items. There are other packages out there for Apple, but I won't make recommendations since I don't own one.


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