Nissan 3.5 dead engine picture

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This is a picture of Nissa VQ35 engine from a 2005 Maxima. It is a picture of the intake port, and what you are looking at is caked on catalyst on the intake port. What happens many time with these Nissan engines is that the catalyst breaks down and gets digested back into the engine (the catalst dust is caking on in the intake port) and then the cylinder walls get washed out and then you have little/no compressions and thats the end of the engine.

IMG00249.jpg
 
Johnny248,

What is the catalyst coming from? I would presume there is a cat in the exhaust stream just before the EGR tap?

Wayne
 
What what I understand is the catalyst is being sucked back into the engine through valve overlap. The engine has as cat attached to each exhaust manifold, and it bounces around and breaks up, it gets sucked back in through the ehxaust
 
Originally Posted By: hate2work

Are you talking about the catalytic converter? It's breaking down and somehow coming back into the engine?

Is this common to this engine?


Yes, the catalytic convertor is being digested back into the engine. It is some what common on this generation maxima, and you also see it happen on the 02-03 2.5L Altimas. They have a recall on some of the units where depending on what was going on, you would get a shield on your cat, a new cat, or a new engine if the catalyst had been digested. The precatalyst breaks down and sucks back into the combustion chamber which wears walls/rings, valves and causes excessive oil consumpition and low compression. It sounds crazy but ask anyone who has owned one of these cars that needs an engine, and they will tell you its true
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Originally Posted By: IndyIan
Sucked back all the way into the intake ports past the intake valves? I wouldn't think it was possible?


There is valve overlap that pushes/pulls back and fourth on the intake and exhaust ports.
 
INTRODUCTION

Nissan has determined that some 2002-2003 model year Altima and 2002-2004 model year Sentra vehicles equipped with the 2.5 liter engine have defects that relate to motor vehicle safety. For 2002-2003 model year Altimas, there is a possibility that the exhaust pipe hanger pin may catch debris from the road that could be ignited by contact with the catalytic converter and cause a fire. In addition, for 2002-2003 model year Altimas and 2002-2004 model year Sentras, there is a possibility that certain engine operating conditions may cause damage to the pre-catalyst. Material from inside a damaged pre-catalyst could enter the engine and result in increased oil consumption. If the engine oil level is not checked on a periodic basis and drops below the low level, and the driver continues to operate the vehicle ignoring noticeable engine noise, engine damage may occur which could result in a fire.
 
I've heard this before, I think even on a TSB.

I don't understand it either, as in... I'm not sure when in the engines operation there is significant enough vacuum in the cylinder when the exhaust valve is open. Startup perhaps. I guess it only takes one small shard of cat to kill a cylinder, so even if it's one in a million it's only a matter of time.
 
Originally Posted By: bepperb
I've heard this before, I think even on a TSB.

I don't understand it either, as in... I'm not sure when in the engines operation there is significant enough vacuum in the cylinder when the exhaust valve is open. Startup perhaps. I guess it only takes one small shard of cat to kill a cylinder, so even if it's one in a million it's only a matter of time.


It is hard to understand, but there are so many things that occuring inside and engine that just your basic vacuum air in, combustion, and exhaust.

The fact is wether anyone wants to argue the idea or not, it is happening and engines are being trashed, I see them all the time here
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Originally Posted By: rcy
How is it that the 3.5 is one of Ward's ten best engines, yet can suffer from something like this?


It may be rated on of the best engines, but everything has it's weaknesses. I see a lot of oil consumption with these engines overtime. The variable cam solenoids are oil driven, and once oil gets low they start making all sorts of noise. Not saying it is bad engine, but you can pretty much chose any car, any engine no matter how good it may be, everything is mechanical and everything is only as good as its weakest engineering or production quality issue.
 
Originally Posted By: rcy
How is it that the 3.5 is one of Ward's ten best engines, yet can suffer from something like this?
easy! it is not an engine defect but a cat convertor defect. i am sure that would be wards defense? mike
 
I rate the ford 2.5L V6 duratec in my '95 contour GL 5M as a better engine than the 3.0 in my 98 maxima GXE. Also, When looking in the oil fill in the maxima V6 the cam showed excessive parting line flash, which I thought was very shoddy and inferior and unnacceptable component part finish.
 
I've heard of it on the Nissan 4cyl 2.5L like the TSB explains, but that's a first for the 3.5L V6.

Joel
 
Originally Posted By: JTK
I've heard of it on the Nissan 4cyl 2.5L like the TSB explains, but that's a first for the 3.5L V6.

Joel


So far all I'm seeing it happen to the 3.5 is on the 04-08 or whatever the last generation Maxima is.
 
Originally Posted By: Johnny248
INTRODUCTION

Nissan has determined that some 2002-2003 model year Altima and 2002-2004 model year Sentra vehicles equipped with the 2.5 liter engine have defects that relate to motor vehicle safety. For 2002-2003 model year Altimas, there is a possibility that the exhaust pipe hanger pin may catch debris from the road that could be ignited by contact with the catalytic converter and cause a fire. In addition, for 2002-2003 model year Altimas and 2002-2004 model year Sentras, there is a possibility that certain engine operating conditions may cause damage to the pre-catalyst. Material from inside a damaged pre-catalyst could enter the engine and result in increased oil consumption. If the engine oil level is not checked on a periodic basis and drops below the low level, and the driver continues to operate the vehicle ignoring noticeable engine noise, engine damage may occur which could result in a fire.


I love how they describe ring damage..."could result in increased oil consumption".
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Cats are evil lol. I like for them to be well away from the engine and down the exhaust pipe. Those pre-converters so close to the exhuast manifold must be seeing reversion pulses that wouldn't as likely be seen further down the exhaust system.

I guess this is just another reason why I liike to change oil every 3 months/3k miles. Although it's doubtful more frequent oil changes would save the cylinders, it couldn't hurt.

Oh yeah Ward's also rated the GM 3.8 a best engine. It had upper intake manifold/EGR stove pip problems and manifold gasket problems. Wards is not really focusing on quality control or ultimate durability history.
 
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