Had a problem of car just choked down then quit. Would throw codes p0305, replaced #5 spark plug and boot assembly. Then engine throw p0300 code but still would not run good, actually poor to no run at all. After going trough a list of 9 corrective measures that involved replacing sensors, the last thing on the list was taking out the o2 sensors. Mine were welded in place so I unscrewed the cat bolts enough to let gasses out and it corrected all issues. So I removed the cats and lo and behold the upper converter had blown into the lower and stopped it up. All fixed.

Turns out the catalytic converter melts and clogs the exhaust. Failed with no warning. The Xterra started idling rough after I filled it up with gas. Thought it was bad gas so I added HEET Red and it cleared up for 24 hours. When I drove to the grocery store on Sunday the check engine light started flashing. Took it out later that afternoon and the engine wouldn't go over 2,000 RPMS. Barely got it home. Got online and it looked the it was the MAF which I ordered. Car sat for a week while I waited for the MAF. Changed the MAF and the idle was still very rough. Was able to get the check engine light to go on. It was showing a P0300 error code for random cylinder misfires, nothing indicating a problem with the catalytic converter. Had it taken to the dealership and they said that parts of the catalytic converter had melted and clogged the exhaust. Cost would be around $2,000 to repair and that they would have to do a compression test to see if the engine had been damaged. It was a 50/50 chance on the engine and that would cost around $5,000. Already spent a few thousand this year replacing shocks, fuel pump etc. Called a few places that take junk cars, highest offer was $910. Thought about it and on Sunday I went and went and bought a KIA Niro. The KIA dealer is across the the street from Nissan. I asked for $1,000 for the car and they gave it to me along with 0% interest $900 in rebates and no pressure to buy the car. Last night I found out that consumer reports rated the NIRO as the most trouble free car of 2017. California just raised the gas tax so buying a car that gets more than 45 MPG made me feel good. They have had one recall and it is a page in their owner"s manual that needs to be updated.

In Jan dealership replaced ECM relay under a recall, didn't tell me. In July vehicle started acting up, took it in, diagnosed bad ECM relay, replaced, charged me, and still didn't tell me it was replaced in Jan. Next day service engine light came on, took it back, they said he cat's were gone and "theses things happen". Started researching, found out there was a recall on the ECM, called the dealership who then admitted they replaced it in Jan. Basically they pulled out a part that had worked for 11 years, installed a defective part, which failed in less than 6 months, when it went it dumped extra gas into the engine which ended up burning off in the cats.