Knock at 4200-4500 @WOT
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Knock at 4200-4500 @WOT 1994 Z28 A4 - Been fighting this problem before I installed LT4 Hot Cam and it's still there. Shows up as 5-10 HP dip on the dyno at 4200 RPM. Freescan and Datamaster show 1-2K knock count bump and 6-10 degrees of retard at 4200 it then clears up at 4500 no more knock all the way to 6K. When it fails MAP is at 97.1 timing at 40. When it hits BLM cell 15 the knock starts, timing retards, RPM drops 100 RPM for a fraction of a second and then it all clears up. I don't have a wide band to see if it's running to lean at that point (causing knock) and the BLM counts are frozen at 128 during PE mode so I can't see whats going on. Is there anything else I should check.
Did you ever desensitize the knock sensor or get the LT4 knock sensor (or both?). Seems to be a common practice. And you got it tuned with the cam to right???
For the future, Don't mod the car unless it is running right. Modding it is just going to make any problems worse (and could add a few too)
For the future, Don't mod the car unless it is running right. Modding it is just going to make any problems worse (and could add a few too)
Thread Starter
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Dragframe, 10-04 on fixing knock prior to the Cam swap, but I figured why tune to the old cam, lesson learned.. Anyways I wanted to gather a few local trips and runs to see if the new cam/RR's caused knock prior to going to the LT4 Knock Module. I,ve set up the idle and upped my timing to 4 degrees accross the main and extended ranges so far and no additional knock anywhere except the original WOT 4100 RPM spot. I guess I should try desensitization, you got any software tricks or should I go hardware LT4 PCM Knock Module route.
i have this same issue. I mean exactly the same rpms and everything. I have the LT4 knock module and also have reduced the knock attack rates by 15%. Still got it! WTF. Have not changed recovery rates yet. 80k miles stock internals BTW did you fix yours yet
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i420tom, No I have not fixed it yet, Actually I was lowering high RPM timing and was out testing it with the scanner attached when another problem popped up. Car just died running at 1700 RPM, scanner went to 4800 RPM for 4 cycles ?? and then everything shut down, would not restart and I had to get it towed home. Looks like Opti went crazy. It started back up with problems next day - go figure. So I have put the knock on back burner for now.. " they call this a hobby ??? " .
My knock shows up when I enter PE mode from BLM cell 15, the trim counts look OK while in 15 (128 to 136), a little lean but within tolerance, so I was thinking about adding PE enrichment to see if more fuel at top end helps the knock.
My knock shows up when I enter PE mode from BLM cell 15, the trim counts look OK while in 15 (128 to 136), a little lean but within tolerance, so I was thinking about adding PE enrichment to see if more fuel at top end helps the knock.
Last edited by bobdec; Mar 15, 2008 at 10:04 AM. Reason: corrected spelling
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