Hello,

This is my first post. I need help with my wife's car if you guys don't mind. It's been a great car, but recently has begun to make a strange sound. While moving, with the engine at low RPMs, the car will make almost a grumbling sound from the engine bay. As the RPMs raise, the sound increases "grumbles" (GPMs?), and then eventually at around 3k RPMS the grumbling stops. This happens in any gear where the engine is under load at low RPMs. I can not recreate the sound by revving the engine in neutral, or by revving it in gear with my foot on the brake. Acceleration doens't seem to be suffering, nor does steering or anything like that. At this point, it is just a noise with accompanying vibration. I have suspected bad motor mounts. I tested them by revving in gear and looking for engine movement. The engine does seem to move excessively (not too bad though), and there is a spot on the hood insulation where the distributor cap is wearing from the engine lurching). But while doing this test, I don't hear any clunking or thuds, or unusual noises. I just did the alternator and idler pulley, (alternator for whining, and idler pulley due to Autozone recommendation I had to raise the motor to get the old pulley out, so I had to D/C some motor mounts to do that. Anyway, my point is that I will do what is needed to fix the car, but would like to avoid excessive work/cost. If you guys have experience with this and are pretty sure it's motor mounts, I'll do what I have to do. If you have a strong feeling it's something else, I'll go that way with it. Let me know if you need further clarification on it, thanks!

PS- My next step is to ride under the hood while my wife drives at a low speed to see where the noise is coming from. If I can avoid that, I'd be most appreciative!

Welcome to NICO!
Unfortunately things like this are notoriously difficult to diagnose over the internet (without seeing/hearing the problem), but here's a few things that COULD be the problem:
Loose heat shield somewhere. Try hitting some heat shields or the exhaust with your fist when the engine is cool.
Timing chain noise. Typically when the KA24DE engine gets to be a little older, the timing chain can rub against the upper guide. You can remove it without worry (free) and see if that fixes the problem. You just have to remove the valve cover to do it.

Thanks for the reply. I'll try doing those things, I already messed around underneath with some stuff looking for looseness, but no luck. It does have 154k on it, I'll look at the guide. Do I need to replace the valve cover gasket if I remove the cover, or can I get away without doing that? Thanks!

Is there supposed to be a bolt here? This is where a motor/tranny mount appears that it is supposed to be bolted to the tranny. It's just below the starter (to give you a point of reference.) If you have trouble seeing it, it's almost perfectly centered in the pic. If so, where do I get this bolt and do you think this would help?

alnen wrote:Thanks for the reply. I'll try doing those things, I already messed around underneath with some stuff looking for looseness, but no luck. It does have 154k on it, I'll look at the guide. Do I need to replace the valve cover gasket if I remove the cover, or can I get away without doing that? Thanks!

Yeah, at 154k, if the valve cover gasket isn't leaking, it will be soon.

alnen wrote:Is there supposed to be a bolt here? This is where a motor/tranny mount appears that it is supposed to be bolted to the tranny. It's just below the starter (to give you a point of reference.) If you have trouble seeing it, it's almost perfectly centered in the pic. If so, where do I get this bolt and do you think this would help?

I'm not exactly sure what I'm looking at there (and I don't have an Altima I can go look at), but you should be able to find it in the FSM somewhere.
http://www.nicoclub.com/FSM/Altima/1995/

My guess is that yes, there is supposed to be a bolt there.

first thought is also heat shield

picture went missing?