Q: My 1993 Toyota pickup has the 2.4-liter four-cylinder. I had a problem where the engine was pinging really badly. It took it to a mechanic who changed the timing. This stopped the ping, but now it doesn't run nearly as well as it did.

A:To keep it simple, a ping or spark knock is caused by an improper burn within the combustion chamber. Actually, optimal performance and emissions occur with settings just before the spark knock takes place. This is why older engines had a lot of ping problems, while late-model technology has the issue under control. With your Toyota, the noise can be caused by a lot of different factors, including engine temperature, ignition timing, a lean air/fuel ratio, and excessively high compression. Start by setting the ignition timing back to specs, while taking a good look at the crankshaft pulley (harmonic balancer). The outer pulley can twist on the inner hub and throw off the timing mark(s). During all this, be sure the engine is running at normal operating temperature. Next find the Exhaust Gas Recirculation valve. Basically, the EGR valve bleeds exhaust gas into the air/fuel mixture to lower combustion temperature and therefore reduce harmful emissions (NOx). I'm not going to get into the full EGR diagnostic procedure, but you must be sure the valve is opening while accelerating. And even if it is, you also have to be sure the exhaust ports from the valve in the intake manifold aren't obstructed with carbon buildup. If the EGR tests well, I'd suggest using a top engine cleaner such as Sea Foam to clean carbon buildup on the top of the pistons. This buildup can raise compression or create "hot spots" in the combustion chamber, which would cause a ping. Start with these suggestions, and get back with me if there's still a problem.


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If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

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