2002 Nissan Pathfinder SE leaves clues but I'm clueless

Like the Mars Pathfinder my 2002 Nissan gives me unprecedented amount of data. I just need experts in the field to help me decipher the code. I purchased the vehicle roughly in 2007 by auction. About 3 years ago, I notice that the car sometimes has trouble turning on but I saw it as a sight nuisance at the time. As I turn the key to start the engine there is a delay and when it does turn on it makes some disturbing noises but this is not a routine occurrence. I thought it might be the battery so I purchased a new one. I had a mechanic look at the car and he said it was the catalytic converters but I’m not sure since it passed the smog test without any problems. The car also trembles at times and releases white smoke from the exhaust pipe. I have looked at the oil stick and it has little bubbles which I’m not sure when that started. My boyfriend seems to think that it has something to do with the spark plugs. I don’t know but would appreciate any feedback from anyone. Thank u.

I Think There’s A Chance That You’re Losing Some Coolant, Internally.
White Smoke, Delay When Starting (Hydro-Locking), Bubbles On The Oil Dipstick, And Car Trembling Can All Be Symptoms.

Have you checked and monitored the coolant level (with engine cold for safety reasons) in the radiator/coolant reservoir ? Do you have to add coolant ?

Do you ever experience poor heater/defroster performance ?

If these are symtoms of coolant being consumed by the engine then it shoul not be started and run until the source of the problem is located and corrected. Severe damage to the engine could result.

CSA

Another Possibility Is Leaking Fuel Injector(s).
CSA

You need an actual mechanic to look at it. I suspect you have more wrong than the cat converters. If it were me, I’d want to check for signs of a headgasket breech, like bubbles coming up in the radiator fill hole with the cap off and the engine running (do this cold please…don’t scald yourself), or dumpy scum under the coolant fill cap (contamination from combustion gasses getting blown into the water jacket).

The typical symptoms of a bad catalytic converter include the illumination of the Check Engine Light and the failure of the smog test. Occasionally one will fail in a manner that creates a serious loss of power, but I don’t see that here. Your cat converters are likely fine.

You should have failure codes stored in your car’s computer, Have those downloaded and post them here. They’ll be a big help.

Disturbing Noises On Cold Start In Nissans With The VG30E And VG33E Engine Can Be Rattling Caused By The Hydraulic Valve Lifters.

A Nissan bulletin lists revised replacement lifters 13231-V5005 (x12) to fix the problem in vehicles with those engines, built before 10/13/03. Do you have either engine ?

CSA