i just bought a 1990 nissan maxima with 71 thousand miles on it and now all of a sudden the engine is makin a little weird noise..the muffler is like rumbling it sorta sounds like and when the car is at a complete stop it feels like something is kicking under it..i was wondering if anyone knew what might of caused this..

 

That description is WAY to vague to even try to help you. Try to write detailed description of the problem, not just 3 lines. If you think you cannot give such an description, have a trusted mechanic take a look.

Remember: Internet diagnostics is one of the hardest things to do.

 

yeah the thing is im a new car owner this is my first car so i dont have a trusted mechanic yet and im in fear of some sorta 4000000$ repair bill..heh..it took me an arm and a leg to dish out 6,000$ for insurance!...new york sucks for insurance...anyways when i am stopped ..like i put my foot on the break peddle it feels like in the middle of the car its sorta like 'kickin' the rpms are jumping up and down a little bit ..when i press on the gas the muffler like rumbles and its a little jerkish..i used eagle one chrome cleaner on the muffler i dunno if that would have anything to do with it..but the rpms jump up and down a little..any help is appreciated

 

go get a PCV valve.... unless you did that (its like a 3 dollor part) that should smooooth things out for ya.. if not .. check for vacum leaks

 

Check these, any problems replace with NGKs...