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Discussion Starter · #1 ·
Hi have a 2006 pathfinder with a po300 code. my patty has no compression. If I floor it I can slowly get up to keep up with traffi..Changed the coils and everything to do with spark. . took it to the shop and the mechanic said it was the catalytic converter so we drilled it out. Still not the problem. Changed mass air flow sensor. I don’t know what else to do. bought a parts truck and going to start changing more sensors and relays. Please help
 

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Welcome to the forum Ronsomatsuo4.

There are many causes for the P0300 (engine misfire) code, as any DuckDuckGo search will show.


There are folks on this website that are smarter than I am, and they will probably be along later. But no one is going to be able to lay their hands on the computer screen and magically diagnose your problem. It will require effort on your part.

You will want to find and download the FREE and COMPLETE Nissan Factory Service Manual. I saved mine as individual PDF’s EACH chapter, on my iPhone, and later on my iPad (easier for my old eyes to read) and on one of my laptops. I also ‘renamed’ the PDF’s to make it easier for me to find the chapters that I needed to study. The FSM is invaluable for diagnosing, and walking you through the exact repair processes of the 06 Pathy, If you are diligent, and can read and follow instructions.

When I fixed my SO’s ‘06 Pathy (a few years ago) with a p0300 code it was an air intake leak, and easy to fix once I tracked it down with the help of the FSM.

The FSM that you seek can be found on the NICOclub website IIRC.

YouTube is also a good place to learn, but you have to be careful as to who’s advice that you follow, as some of them are just plain wrong, as was the ‘mechanic’ who instructed you to drill your catalytic converter. I think it’s unfortunate that you ‘Drilled’ you catalytic converter, because once you fixe the P0300 code, your Pathy is probably going to throw another code for the Catalytic converter.. I’ve heard that those are not cheep to replace.

Good luck in your endeavors!
 

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You said the truck has no compression, was a compression test performed? It wouldn't run if it has no compression.

If it's not a coil or plug, then it could be an injector, fuel pump, vacuum leak, head gasket or low compression.

Your scantool might be able to read mode 6 data, where it should show you a misfire counter based on cylinders to see where the most hits are.

It sounds like the mechanic was guessing. There are tests that can be done to determine the actual issue.
 

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Discussion Starter · #6 ·
You said the truck has no compression, was a compression test performed? It wouldn't run if it has no compression.

If it's not a coil or plug, then it could be an injector, fuel pump, vacuum leak, head gasket or low compression.

Your scantool might be able to read mode 6 data, where it should show you a misfire counter based on cylinders to see where the most hits are.

It sounds like the mechanic was guessing. There are tests that can be done to determine the actual issue.


thanks man and yes everyone was just guessing and paid mechanic to find problem he said cat converter. Did that then he says muffler! I’m so over it plus I work 7 days a week I have to make time for this
 

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Easy way to test his theory is to either measure exhaust pressure in the a/f sensor port, or just disconnect the front exhaust and see if power is restored. When the convertors break apart, it's possible for the pieces to clog farther back sections of the exhaust.

The p0300 means that the ecm can't tell which cylinder is misfiring, but it should show up in the mode 6 misfire counter to give some direction.

Quick and easy check, make sure your engine oil level isn't too high. The crank doesn't like having to plow through too much.

There is a lot that can be tested, but you have to have some basic test tools.
 

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Discussion Starter · #8 ·
Disconnected the muffler and still no power. Thanks for all the info I will invest in tools to measure the exhaust pressure. And also to read codes 6 misfire. Just took off catalytic converter on exhaust manifold and wish I read this first I have cats from a frontier of the same year but plug is different. Before I order o2 sensors blindly I will do some test. I really appreciate you guys
 

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Discussion Starter · #9 ·
Hey you guys Sorry been working 7 days a week and did not invest much time in the pathfinder. I food notice a cracked rubber hose between the egr sensor leading to the dpfe sensor. So I unbolted is and there is a loose piece that I could remove by hand. Just wanted to get an opinion before I spend the money to change it. Do you think this could be the cause for a random mid fire?
 

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A vacuum leak can definitely cause a misfire. Easy to test once you get a scantool that reads live data. A Bluetooth dongle from Amazon for $10 and a $5 app is all you need!
 
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