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2006 Maxima dieseling (knocking) head gasket going to fail?

I have 2006 Nissan Maxima SE with the 3.5 engine. I have used regular gas for the entire 88K miles. Lately the engine knocks (diesel like). I asked my guy what to do. He said a nitrogen fuel injector cleaning… Did that. No change. When I use premium it stops. However, I suspect something more is wrong. In fact, I suspect a head gasket issue. How can I diagnose without going to the garage? If it is the head gasket, am I doomed (cost a fortune to fix).

I should add some detail. The knocking is at low rpm, sort of off the line. The car seems more sluggish than in the past. Also, I smell coolant in my garage after the car is parked there for a while. My 1998 Windstar smelled similar before “dying”.

This sounds like either a knock sensor or EGR system problem. This can occur without illuminating the CEL or setting any codes. Don’t worry about head gaskets.

ok4450, could you recommend my next course of action to fix?

As usual, I believe that ok4450 is right on target.
Cleaning the EGR valve would be an excellent first step.
If that doesn’t stop the problem, then replacing the knock sensor would be a good next step.

And, of course, old eroded spark plugs could explain both pinging and sluggishness.
When were the plugs last replaced?

The head gaskets might be a problem, but at this point, I don’t see it as being likely–especially on an engine that doesn’t have a history of that type of problem. The smell of coolant is likely from a weeping hose connection (check all of the hose clamps), or even from a pinhole leak in one of the heater hoses.

Is the car actually losing coolant, as indicated by the level in the overflow reservoir?

The plugs are original. As for coolant, I don’t see signs of lost coolant. It’s the smell and my memory of that smell that had me thinking about it. The oil looks good too. Not white or milky at all.

“The plugs are original.”

…and you don’t think that after 8 years of use, and after experiencing pinging, you should replace them?

You could also have combustion chamber deposits causing the knocking. The Nissan V6 seems to be sensitive to octane, they’ve been recommending premium for years - what does your owners manual say?

Click and Clack addressed this on (almost) your exact car:

Thanks guys… I will follow the recommendations and keep you posted.

I also will use the premium…yikes, an extra 10 bucks every fill up! Do octane boost product work as an alternative?

@jr4488 in a word…no. Keep using premium if your vehicle owner’s manual requires it. Follow the advice of @VDCdriver and get your engine back in proper running order. BTW…dump the guy who suggested a nitrogen fuel injector cleaning. All he did was clean your wallet.

A problem with a knock sensor or EGR fault should still not be ruled out. Actually, that car should run on 87 with little or no problem in spite of any 91 recommendation.
There has been somewhat of an issue with knock sensors on these cars anyway and at 8 years of age it’s entirely possible to have a clogged EGR port or stuck EGR pintle.

Maybe getting the codes pulled at a local chain auto parts store could be done. It’s possible anyway that something could show up in spite of no CEL and it’s free of charge.

For what it’s worth, a friend of the family has owned, and currently owns, Maximas of this vintage and runs nothing but 87. He drives the cars hard and has had no pinging problems even with the car loaded and on trips through the mountains on the way back and forth to NYC.