WarMonger

Hi all. I have a 99 maxima GXE with 77k miles on it. Recently it was "tuned up" by a local repair shop, and since then there's a rumbling sound around 2-3000 rpms. Its pretty predictable, like 2100 is when it sounds like a muffler rumble but it's in the engine. My question is would that be a knock sensor symptom? The shop showed a knock sensor fault code and wanted to replace it, but I didn't let them seeing as it's like $200 for a new one. What symtoms are there when the KS is bad? I've been searching the web for more info, but can't find what I need. What's the best bet for my car?

Thanks,
Dan

njmodi

iTrader: (4)

Welcome to the ORG. Since you are serious about asking for help (you donated), I'll do my best.

Do you know what all items the tune-up consisted off? Do you know what brand/part number spark plug they used (if they replaced them?)

A bad knock sensor typically will just retard timing - so the most noticeable side effect is that your car feels sluggish all the time. A bad KS will not cause any rumbling sounds.

Is your car a auto or 5-spd?

Does the sound happen while in neutral (i.e. not moving?).

Are you sure it's not a pinhole leak in the exhaust system? -> What makes you so sure it is coming from the engine? (I'm not patronizing you, I'm just asking to see if there is something more specific that you noticed but failed to mention in your original post).

Does the engine vibrate when you hear the rumble? (i.e. have someone else apply throttle while you observe). Obviously this is only possible if you are able to duplicate the sound while at a standstill.

Are there any driveability symptoms with the rumbling?

WarMonger

It's an automatic. I believe they changed the filters/plugs (platinum) and ran the diag. machine. It came back with KS code, which I double check with a friend who had a code machine. There isn't any problem while in neutral. Its apparent only when in gear and only at 2100-3000 rpms, through all the gears. I'm assuming the "rumble sound" is a vibration because I can feel it through the gas pedal. Acceleration has been sluggish, esp. when shifting it seems, and I get that sound just before it shifts. It's like a deep "errrRRR.." but it stop after 3000. I appreciate any help or tips you can give...Thank you

njmodi

iTrader: (4)

As you can probably imagine, diagnosing sounds over the internet is not trivial. Perhaps you could post a sound clip?

If it only happens in gear, you might have a transmission issue... have you ever changed the transmission fluid?

Do you know if the shop used NGK platinum plugs? There are many other platinum plugs available (which they could have used), which are not the correct ones for your engine.

It could also be something like a bad motor mount - which happens to be resonating at those RPMs...