96 Grand AM GT with 2.4L DOHC & 5 speed sat for a year at dealer with ABS problem. Auction car I bought. Replaced fuel pump, heater core and intake cam seal. Car runs fine but has loud to moderate "slapping" noise that is RPM sensitive. It seems to be coming from the timing chain end of the engine and is not affected by oil weight. Virtually the same with Walmart 5W30 or 20W50. The noise will sometimes taper off to almost nothing then all of a sudden come back with a vengance. Was suspecting timing chain chain slap but can't see problem there when enging running and chain cover loosened for viewing chain. Inspected oil pump chain and although seemed loose, there is no problem there. Adjusted chain tensioner to slightly tighten. Cams, lifters and valves visually look ok. However, that was just a visual inspection. Noise could be coming from 1 or 2 cylinder area though. How do you check a hydrallic lifter to verify it is pumped up and working properly?
Also, any other ideas on what the problem might be other than lifters? And how do you check for those 'other ideas'? Thanks all. RLJT60

96 Grand AM GT with 2.4L DOHC & 5 speed sat for a year at dealer with ABS problem. Auction car I bought. Replaced fuel pump, heater core and intake cam seal. Car runs fine but has loud to moderate "slapping" noise that is RPM sensitive. It seems to be coming from the timing chain end of the engine and is not affected by oil weight. Virtually the same with Walmart 5W30 or 20W50. The noise will sometimes taper off to almost nothing then all of a sudden come back with a vengance. Was suspecting timing chain chain slap but can't see problem there when enging running and chain cover loosened for viewing chain. Inspected oil pump chain and although seemed loose, there is no problem there. Adjusted chain tensioner to slightly tighten. Cams, lifters and valves visually look ok. However, that was just a visual inspection. Noise could be coming from 1 or 2 cylinder area though. How do you check a hydrallic lifter to verify it is pumped up and working properly?
Also, any other ideas on what the problem might be other than lifters? And how do you check for those 'other ideas'? Thanks all. RLJT60

By the way, even though the knocking faded in and and out it turns out the problem was a spun rod bearing in #3.