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Message: <blockquote data-quote="SlowRider" data-source="post: 1509609" data-attributes="member: 29436">I am back to this thread as I continued diagnosing the timing/pinging issue with no success. I have checked all the grounds, PCM, replaced all the ignition components but still the car pings/knocks. However, I have noticed a few things about this issue. First, jerking of the voltage needle is related to the engine vibrating/jerking during idling. This additional vibration is periodic and in addition to the normal vibration from the engine. I believe somehow there is a misfire although it passes cylinder balance test. This happens with or without the spout connected but more with the spout connected and I believe is causing the timing to be erratic under timing light. Also, the excess vibration goes away at higher rpm. Second, it seems that this problem is temperature dependent. It pinged a lot during summer (80-90F) under any sort of acceleration with the spout connected. So I took the spout connector out during the summer which makes it ping less and keeps the car drivable. However, as the temperature dropped (50-60F) in last couple of weeks it pings much less even with the spout connector in. Also, pinging/knocking is virtually absent when I drive the car first time in the morning with cold engine. As the engine warms up the pinging/knocking comes back. During the KOEO test the only code shows up is 564 which is cooling fan circuit related (although the fan runs in low and high speeds during the test) and nothing else. KOER test pass successfully.I am looking for a powertrain control/emission diagnostic manual for OBD 1 to be able to diagnose this correctly. It makes me wonder if EGR could be the culprit. Any suggestions/inputs will be much appreciated.</blockquote>