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Maybe your problems are corrected with a new engine but did you ever inspect the cats? The following is my experience.
Buying and driving cars always in the end boils down to economics, time involved in repairs, and safety. For years I drove brand new GM vehicles because they seemed to have the best repair records versus initial cost. I then began to buy 2nd hand cars. However the last GM vehicle I had was a GM Saturn that eventually had a subframe front bar that you could have literally karate chopped in two because it was so thinly made and rusted to the point that I was lucky it didn't break and have my engine literally drop to the highway while driving. That happened at 252000 km. That was the last time for any GM product. The thinking here was if that was GM's attitude about safety then I wanted no more to be a part of their vision. The next car was a Honda Civic that I got 2nd hand with 200000 km on it. I finally had to get rid of it after another 30000 km because the head gasket went and I was having to resupply antifreeze every time I drove the car. Also the motor was burning oil about a litre every 5000 km. So that car had 232000 km on it before I decided to get rid of it. I figure a car should give you 400000 km in places where they salt the roads (much more than that in places like Arizona and Cuba) if you rustproof it from the beginning and 300000 km if you don't. Since I bought these cars secondhand I at least expected 300000 km out of them. Didn't happen. So I now have got a 2006 Altima that I just recently bought that had 68000 km on it. Even though the car had never been rustproofed I figured with such low mileage on it I couldn't lose because I got a steal of a deal. However in 3 months I have had to put $5500 Canadian into it. Basically the 3rd generation Altimas were a lemon. However with careful planning and good maintenance and some luck, I think I can get to my target of 300000 km. The previous owner never rustproofed it and that was a big mistake as these cars are known as Fred Flintstone cars. There was a design flaw with the floorboards rusting from the inside out that Nissan only corrected in 2007 when they redesigned the Altima for the 4th generation. That fact is the basis of a class action lawsuit in the state of Illinois on behalf of all 2002-2006 Altima owners in the state OF Illinois. We will have to wait for the verdict and how it will apply to owners outside of the state of Illinois if the suit is successful. In the meantime I had to spend $900 to put new steel plates in the floor on both the front drivers side and passenger side. The other major problem with the 2002-2006 Altimas and some Sentras was the fact that the crankshaft position sensor was made with a cheap plastic housing that cracked under high heat and began giving faulty signals to the ECM. Nissan ignored the problem for 5 years until there were so many Altima and Sentra owners who were bringing their cars in under the warranty, that they finally redesigned the sensor in late 2006. My car was one of the last on the Smyrna, Tennessee assembly line but it seems that Nissan never replaced the sensor on the factory floor until the 2007 model year. Nissan finally had to do something because they were faced with a 100 million dollar problem of replacing over a million crankshaft position sensors on both models of cars. They came up with the idea of reprogramming the ECU so that the ECU basically ignores any signal that it gets from the crankshaft position sensor. This was a lot cheaper than installing a new redesigned part in a million cars. Officially there were about 800000 cars on the official recall list but there are many horror stories of many early Altima and Sentra owners never getting a recall letter because their VIN number did not show up on the list. I don't have an exact figure on the number that were left off of the list but based on sales there should be at least 200000 more owners around the world who had a bad crankshaft position sernsor. The early Sentras and Altimas both had the same QR25DE engine with a crankshaft position sensor measuring the crankshaft angle and engine rotation speed located in the engine block and a camshaft position sensor which is exactly the same part number as the crankshaft sensor but located in a different place near the camshaft. Nissan changed the factory service manual in late 2006 to reflect the fact that they had all the owners bring in their cars for reprogramming. The manual states " When the crankshaft position sensor (POS) system becomes inoperable, the camshaft position sensor (PHASE) provides various controls of engine parts instead, utilizing timing of cylinder identification signals." Seems like a lawyer wrote that clause. Some owners had wanted their sensors to be replaced by the new redesigned sensor instead but the dealers wanted to charge them $400 even though the cars were under warranty. When the dealer said that the car would be reprogrammed for free, 99.9 % of the owners opted for the reprogramming. The problem is that during the time that the faulty crankshaft position sensor was sending garbage to the ECU all hell was breaking loose inside the car with DTC codes constantly popping up and the owners bringing back their cars to see what was wrong. The recall went out in November 2007. So in the case of my car the previous owner had driven it for 14 months before he received the recall letter. Some other owners especially the early 2002 Altima and Sentra owners had been driving their car for 5 years with the problem. There is no way of knowing exactly when each crankshaft position sensor on any of the cars went wonky but any owner who drove their car fast and on long drives probably were in a worse position. To top this all off QR25DE are interference engines along with every other engine that Nissan makes. These engines give better gas mileage because the valves are allowed to invade the same space that the pistons occupy(at different times of course) so that the air flow is optimized for ultimate clean efficient engine combustion. However this necessitates making the tolerances so fine in engine design that the intake and exhaust manifolds are both open at the same time twice for a fraction of a second on each engine 360 degree revolution. This wouldn't be a problem if there was nothing to be sucked back into the engine. However since every car now has to have a catalytic converter( the Altima has 2 cats); if the honeycomb material breaks down inside the cat that is next to the exhaust manifold, it will get sucked back into the engine with eventual engine failure. The longer the period of time that the faulty crankshaft position sensor's information was being sent to the ECM the more likely that the cat would heat up too high having to deal with the incompletely burnt fuel from the engine cylinder. In that case fragments would get sucked back into the engine. The internet is full of stories where an Altima or Sentra owner would be driving without problems for up to 150000 km (some a lot less) and suddenly they get DTC codes and Service Engine Soon lights and they get the bad news from their mechanic that their engine is unrepairable. So knowing the above facts, I on a hunch took my 2006 Altima into my local garage to check on the cats. The mechanic put the car on the hoist and pulled off the back cat and as he was doing so, pieces of the cat dropped out. This was not catastrophic because these pieces would never get past the 1st cat. However when he took off the undercover of the 1st cat that is bolted onto the exhaust manifold, we saw a burnt spot on the honeycomb as large as a quarter. The mechanic told me I might be lucky that nothing got sucked back into the engine. He said that if I had driven it much longer I would have risked engine damage. So my hunch was right. The Nissan dealer and their mechanics said that the cats should last forever on these PZEV(Partial Zero Emission vehicles) vehicles. Nissan however only gives a 8 year cat warranty, even though in California the exact same car has a 15 year warranty mandated by the state of California. Cats normally should last a very long time but not when faulty crankshaft position sensors are sending garbage to the ECM. It cost me $2400 to replace the 2 cats plus 2 oxygen sensors, but I may have saved a potential engine cost of $5000 Can from a blown engine. I have heard that excessive idling causes cat failure but nothing about this in the owners manual nor have I read it anywhere. So there are 2 possible causes for my cat damage. The previous owner idling his car or the fact that sometime in the 14 months before the crankshaft position sensor was disabled through reprogramming, the sensor had started to go bad. Either way these conditions wont happen in the future of this car. The problem remaining however is that there are 800000 Nissan vehicles out there without a functioning crankshaft position sensor. It makes me a bit uneasy that my car is one of them (it is like having only 1 kidney). As long as the timing chain doesn't stretch and the camshaft position sensor does its job then things should be fine but I'm thinking maybe I should get the timing chain, guides, and tensioner and sprockets replaced in another 50000 kilometres as a preventive measure. Nissan says that the timing chain will last the lifetime of the car but I have known Altima owners who have had to replace the timing change after 200000 km. Note that the timing chain is still working all the time you are idling so if you idle a lot it is the same thing as doubling your mileage.
Last edited by korner; 01-06-2016 at 05:15 PM.