Questions and Answers

Datsun Pinging Q. Hello: Ever since I've had this truck for the shop, 1981 Datsun King-Cab two wheel drive M/T, A/C, Z-22 8-spark plug engine, it's always had a pinging problem. I've tried everything including higher-octane fuel; "it helps some" and retarding the timing down from factory five degrees to three degrees and pinging still.

Lowering the timing even two degrees greatly reduces the power of the truck and the acceleration or torque curve moves to the upper rpm area, and I loose all low end power, what power there is.

Really frustrated as I've got 160/180 per-cylinder compression, spark is perfect, advance is perfect, fuel CO and HC is within California requirements, and I've tried several carbon cleaning deposits chemicals thinking there's a buildup causing the pre-ignition.

It's mostly noticeable when you first take off even under slight load it knock, knock, knocks, until you get rolling and from second on up as long as one doesn't lug the engine it won't ping. But I've never had an engine even other Nissans knock, or ping like this one does.

In thirty years I've never encountered this, except some Cadillac's that had the 472 engines that would tend to get loaded up from Grandma or Grandpa tooling only around town for ten thousand miles and the engine never saw three thousand RPM to clean all that buildup out.

We've run a can of GM carburetor-clean through it and at the end drowned the engine out through the carburetor and stall it, let it sit for eight hours and drive it seventy or eighty for five miles on the freeway and it was smooth as a Swiss watch for some time. We did this at a dealership too. It worked and I'm not sure a little 2.2 Nissan engine would be able to stand the same treatment if indeed that is the problem.

I should be able to run regular unleaded in this vehicle, but NO way, it would ping and knock every step of the way. ANY suggestions or Nissan insights you might have would be appreciated. Also know I'm willing to recheck some things if you'll make those suggestions to me to double check and how too do them your way might bring about some change or improvements.

Many Thanks,
Paul

A. The dual plug ignition system is designed for fuel economy. It uses a leaner mixture and uses two spark plugs to insure ignition. When the engine is under a load, the ignition module shuts off spark to the exhaust side spark plugs to avoid pinging.

There are a few items that control the timing on that engine, not the least of which is the ignition module. Before you do anything, you have to make sure all the vacuum lines are properly connected and in good shape with no leaks at all. Also, make sure the exhaust coil is connected to the exhaust side of the distributor and the intake coil is connected to the intake side of the distributor. If this is not done, there's no sense checking anything else.

First thing to check is the Thermal Vacuum Valve (TVV). This controls the ignition timing as the engine warms up to operating temperature. To check it:

1. Connect your timing light and start engine when it is cold.
2. Check the timing while the coolant temperature indicator reads below "C", then run engine until pointer on gauge reaches middle position.
3. The timing should advance as engine warms up. If not, replace thermal vacuum valve.

Then check the Vacuum Delay Valve (VDV):

1. Remove the vacuum delay valve.
2. Blow air from port on distributor side. Air should flow freely.
3. Blow air from opposite port. Resistance should be greater than in step 2.
4. If condition of valve is questionable, dip port in water and blow air from brown face side. Air bubbles should appear.

Check the Distributor Vacuum Advance:

1. Connect your timing light.
2. Connect hand vacuum pump to the vacuum advance unit.
3. As you apply vacuum the timing should advance and go back down when vacuum is removed.

Check the Vacuum Advance Control Solenoid

1. Remove both hoses and harness.
2. Remove vacuum switching valve attaching screws and remove valve.
3. Apply battery voltage to valve and ensure that air flows through valve properly.

Now if everything checks out okay, we have to look at the ignition module. For a quick test unplug the exhaust coil and take it for a ride and see if the pinging goes away. If it does, replace the ignition module with Nissan p/n 22020-W0560.

Additional Information provided courtesy of ALLDATA