Questions and Answers

Pinging Nissan

Q. I have a 1991 Nissan truck 4 wheel drive 4 cyl. 2.4 liter 12 valve motor with 130,000 miles. I have two problems. One is when I am pulling a trailer or going up a long hill the valves or something in the top end of the motor starts ticking. I use 93 octane fuel and have used hotter spark plugs. Also I use 10w30 motor oil. The other problem I have is when the motor warms up it idles high and will hesitate and miss when you first accelerate when changing gears in the 5 speed transmission. Any information is greatly appreciated.

A. It doesn't sound like a valve problem, it sounds like the engine is pinging. Pinging, or technically called pre-ignition or detonation, is when the fuel mixture ignites prematurely. This can cause burnt valves and burnt pistons. I have seen this condition burn hole right through the tops of pistons.

Some causes of pinging is excessive stress on the engine, such as towing or steep hills, overheating the cylinders. A hot spot in the cylinder, too low an octane fuel and ignition timing being off are other causes.

In your case you have the problem of towing and steep hills. The higher octane fuel would help, but the hotter spark plugs won't. If anything you should go to a colder spark plug to help heat transfer. I would highly recommend using NGK BPR6ES-II spark plugs in that engine. If you use any other brand, you will have pinging problems, especially Champion spark plugs.

I would also recommend that you have the timing adjusted to specs. That 2.4 liter engine does not have a lot of torque or extra power, so be sure what you are towing does not exceed the capacity of the truck. If the engine is set up properly, you should be able to use regular gas in that truck without having it ping.

I think you'll find that when you resolve the first problem, the second one will disappear.