[dajrdappa]

Yea i have 99 nissan altima and there is a knocking sound from the engine when i start it up. This only occurs when the car has not been start after about 5 hours. When i start my car it knocks then there isn't any knocking but if i turn it off and restart it again it doesn't knock. I just serviced my car thinking it maybe be some bad plugs but sure it enough it didin't change anything.

 

[jserrano]

Sounds like bad piston rod bearings. Pull off the oil pan and you should be able to shake the piston rods to see which is bad.

 

[jrooga]

Sounds like bad piston rod bearings. Pull off the oil pan and you should be able to shake the piston rods to see which is bad.

hi i know this is an old post but i just had the same problem this morning when i started my 99 nissan altima and it did sound like a rod knocking but knocked twice and stopped. i did have a recent oil change within the last couple weeks with high mileage oil the vehicle has over 296,000 miles on it and seems to be still running strong. When i got the oil changed they had to use a thicker oil since they did not have the oil needed for my vehicle at the time and i opted for thicker oil instead of thinner since the vehicle has so many miles. so would this be the same rod and piston problem or maybe just thicker oil? I keep up with regular oil changes as well as the previous owner and i have only replaced the egr valve, backpressure transducer, and the a/c condenser. thanks in advance

 

[amc49]

It's not thicker oil, that runs fine in them. The engines DO eventually wear out.