Poobah Posted April 10, 2005 Report Share Posted April 10, 2005 I posted this issue about a month ago and received some good suggestions. Unfortunately, the problem persists. Hopefully, somebody can shed some light on this baffling problem. For quite some time, I have had an intermittant case of detonation on part-throttle acceleration. It only happens every once in a while so it's been very hard to track down. I finally got a diagnostic customer snapshot of it. The snapshot data said: 1. PD41 = 0 (The knock sensor did not detect any knocks even though my ears sure as hell did!) 2. PD40 = 0.00 (There was absolutely no spark retard resulting from knock sensor data this time. All snapshots I've taken when I wasn't hearing detonation showed between 1.5 and 9 degrees of knock sensor retard.) 3. PD08 = 23 (The spark was running about 5 to 8 degrees more advanced than any snapshots taken when I didn't hear detonation.) Other pertinent information: I give it a WOT at least 3 or 4 times a week (because it's fun). I always use premium gas. No codes are being set. I replaced the EGR valve about 20,000 miles ago and cleaned out the passages and "mouse holes" in the intake and phenolic spacer shortly after that. The car recently passed California's smog test. The car has absolutely no drivability issues - it runs like a dream. I've heard no detonation for, maybe, two or three months and thought the problem had gone away. All of a sudden, it's back. The only thing I can think of that's changed is the weather has warmed up a little. From the snapshot, it seems that something in the knock sensor/spark retard circuit stops working for a moment causing the spark to run too advanced. I suspect the knock sensor is acting up because it wasn't reporting detonation yet I could hear it as plain as day! I can get a new knock sensor from GMPartsDirect.com for about $45 including S&H. Book time to replace it is 3/4 hr. Total cost about $100. I wouldn't mind replacing it but a bad knock sensor should set code P131 and knock sensor circuitry problems should set code P132. I have not gotten either of these codes, ever. It's a real puzzle. I'm hoping somebody can help me find the answer. Thanks in advance Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
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