‘99 GMC Suburban K2500 454 Pinging/Light Knock


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Aug 15, 2020
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My ‘99 Suburban has 98k miles on it. Recent changes made: K&N Cold Air Intake Kit, Bosch Injectors, Custom Tuned ECM UltraPower GM / Workhorse 7.4L Vortec (454) Custom Tuning and a new radiator. Radiator needed replaced. Reason for the upgrades were to improve performance while towing my camper (8,500 Pounds Loaded). First time out after the upgrades the Suburban began running rough with a light knock, loss of power and noticed the passenger side floorboard was hot. Check engine light came on, but when I plugged in a computer to read the code(s) no code(s) were given and the check engine light went off. All gauges read fine during the tow. First thought was the catalytic converter. Had a back flow test done and it was spot on, so it’s not that. Checked my oil level and noticed it was a little over a quart low. Oil level was fine prior to the start of the trip, so within approximately 400 miles I lost a little over a quart. I’ve been running 5W-30 High Mileage Synthetic. Had a guy tell me since I’m pulling with it the 5W-30 may be to light and recommended I use 10W-30. Any ideas what may potentially be going on here? I added about a quart and a half of 10W-30 High Mileage Synthetic, but still doesn’t run smooth and still has a light knock. For about the first 30 miles after adding the oil I didn’t notice the knock. I know what I added wouldn’t solve the problem due to the fact there’s more 5W-30 than 10W-30 in the motor. Could the oil be causing my issues? I appreciate any and all feedback/advice. Thank You!!!