Car ping or knock

What would make my 2003 Nissan Maxima knock, or ping, at around 35-45 MPH? I use high test gas, as manual suggests. I now have 137,000 + miles on it.

Some possibilities include:

A non-functioning knock detector
A non-functioning EGR valve
Spark plugs in need of replacement
Carbon deposits in the cylinders

All that sounds like it would be expensive to fix! Especially the carbon deposits. Right?

When’s the last time the spark plugs got swapped? I’d look there before I started worrying about the expensive stuff.

There’s a liquid engine treatment called Sea Foam ($10 a can at your local auto parts store) that can help break up carbon deposits.

Not saying that you do have a carbon problem, but if you do, a can of Sea Foam may help.

Ok. Thanks again.

“All that sounds like it would be expensive to fix!”

I did not mean to indicate that ALL of those situations existed with your car.
I gave you the four most likely scenarios, and hopefully only one of them is the real cause of the problem.

However, if your definition of “this is too expensive to fix” includes simply replacing spark plugs, then perhaps we have found the problem, namely poor maintenance.

When were the spark plugs last replaced?
Is this car maintained in strict accordance with Nissan’s maintenance schedule?

Is you car a manual or automatic?

In most cases an EGR system fault is the cause of this and it needs to be corrected. Severe or chronic pinging can damage an engine.

First step may be to get AutoZone, Checkers, or a similar parts house operation to scan the car for any codes. They will do this for you free and keep in mind their job is to scan and provide you the codes; NOT to diagnose the problem.
Sometimes an EGR problem may exist without leaving any codes.