What makes a car engine ping? Several reasons makes the engine ping, however the reasons will depend on the condition. If the engine produce pinging noise when driving uphill but no noise when driving on normal roads, it means the fuel you use is a low grade fuel or the air that comes in the combustion chamber is thin.
Pinging noise is usually related to an engine problem, also pinging can also related to low octane gasoline especially while driving uphill. A low grade gasoline with and octane rating of 88 and below can cause the engine pinging noise because low octane gasoline tends to burn quickly or will self-ignite just before the piston reaches the top of the combustion chamber, this phenomenon is called pre-ignition. Pre-ignition usually happens when the engine is extremely hot and under stress like when driving uphill.
Other reason of pinging noise when going uphill is thin air. It is a fact that the air on high altitude is thin and when the engine is under severe stress like when driving uphill because the air is thin the fuel will self-ignite in the combustion chamber earlier than it should be thus pinging sound occur.
To solve this problem is to try to use a high grade gasoline such as gasoline with 92 octane and up. You can easily found the rating printed on the front of the gas pump. Gasoline with higher grade tends to resist pre-ignition because it burns slower. Since there is no pre-ignition then there is no pinging sound.