Spilly Posted January 30, 2009 Report Share Posted January 30, 2009 Alright. Ever since I got this car it's done this, and I've put probably 3500 miles on it and did one oil change since I got the car. When the car is cold, the oil pressure will sit just over 40 Psi, when it's warm, idling in park it will run 30-35, and if I increase RPM's to around 2500-4k slowly the engine seems to vibrate more than normal and make pop/knock sound, but not once per revolution like a rod knock, it does it very sparingly, say if I held it at 3500k for 15 seconds, it would only make the noise once, maybe twice. Now, when it pops, the engine flexes a bit, it's visually noticeable. What's going on here? Piston slap? Bad gap on the plugs? Backfire? It sounds like it's coming from the top end. The really weird thing is, the car still has awesome power, doesn't make the noise under load (when accelerating) even at redline. Any ideas would be appreciated, my grandfather is an automotive guru, heard it and didn't think it was a big deal or significant, but it gives me the creeps hearing that. Quote Link to comment Share on other sites More sharing options...
Pontiac6KSTEAWD Posted January 30, 2009 Report Share Posted January 30, 2009 Holly double post BatMan... Piston slap, or a bad misfire. When was the last tune done? Quote Link to comment Share on other sites More sharing options...
Spilly Posted January 30, 2009 Author Report Share Posted January 30, 2009 It got new Bosch wires 1k miles ago but other than that, the plugs look like they've been in the block for awhile. Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 30, 2009 Report Share Posted January 30, 2009 Motor mounts? Quote Link to comment Share on other sites More sharing options...
Pontiac6KSTEAWD Posted January 30, 2009 Report Share Posted January 30, 2009 That would be the place to start then. plugs, diaelectric greese on the terminals, PCV valave, and check the air filter. Quote Link to comment Share on other sites More sharing options...
Spilly Posted January 30, 2009 Author Report Share Posted January 30, 2009 Air filter is good, Pcv would throw a code wouldn't it? Plugs are so far my guess. Motor mounts are in damn good shape, I imagine they were replaced not too long before I got the car. Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 30, 2009 Report Share Posted January 30, 2009 While it's running, pull the OIL FILL cap and put the palm of your hand over the oil fill hole in the valve cover. If it starts whistling, then the PCV is leaking or bad. Quote Link to comment Share on other sites More sharing options...
Spilly Posted January 30, 2009 Author Report Share Posted January 30, 2009 Will try that tomorrow, neato. Quote Link to comment Share on other sites More sharing options...
ManicMechanic Posted January 30, 2009 Report Share Posted January 30, 2009 Learned that on my L27 Silhouette. A bad PCV won't throw a code though. Quote Link to comment Share on other sites More sharing options...
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