People who've had false knock..
 

Wanted to see who's had it and what it turned out to be.

Valve train noise?
Exhaust leak?
Sensor installed too tight?
Incorrect sensor?
Other?

This isn't for my car, I'm working with someone who has knock, but the data is inconclusive on whether it's false or real (I'm getting conflicting indications that it could be false or real) . Engine is an ANJF 90-92 style speed density TPI. Knock sensor has been replaced with an factory GM unit, correct p/n for the application. Spark timing has been verfied at the distributor and the spark advance part of the tune is factory. Engine is not running lean as the BLMs are doing pretty good.

Re: People who've had false knock..
 

The transmission geartrain in 2nd gear in the 4L65E in my Express van.

No knock retard in 1st gear, knock retard in 2nd gear, 3rd gear it was gone. Trans died a few thousand miles later. Swapped in a 4L85E and magically no more knock retard.

My spark map was the same as a GMPP HEI distributor used in the 330 HP 350 HO and ZZ4 at the time. I got fed up one day and tested WOT to 111 mph in 3rd gear at 4,500 rpm and it was knock free on the same timing value that was showing 6-8° retard in 2nd gear. The false knock was so bad it would put me in the low octane spark map.

https://cimg1.ibsrv.net/gimg/www.thi...0de8cbd1fa.png

Re: People who've had false knock..
 

Re: People who've had false knock..
 

As the owner of a 91 TA 5.7 with spark knock (not sure whether it's real or not), why would a new ICM eliminate spark knock? I've had my ICM tested and it checks out fine. Also, the poster in the link stated he adjusted his timing to 9 deg BTDC....that should increase spark knock, not lessen it, right?

I'm at 6 deg BTDC and running 93 octane fuel....even added an octane boost to increase it more. BLM's are more on the rich side right now while we try to determine the source of the knock (or phantom knock). Tuner Pro still shows a lot of Knock Retard and a lot of pulled back timing resulting in really bad 1600-2000 RPM performance. Disabling the Knock Sensor from the ECM calibration makes the engine run great at all RPM's. Cannot figure this one out.

Re: People who've had false knock..
 

how common is it for the knock filter on the memcal to go bad?

Re: People who've had false knock..
 

Re: People who've had false knock..
 

Tire spin can produce false knock reports. Cracked accessory bracket or loose accessory bolt will do the same.

RBob.

Re: People who've had false knock..
 

Re: People who've had false knock..
 

thanks Tuned. what is the actual failure mode of these things? is it visually detectable like a broken solder joint or something like that?

Re: People who've had false knock..
 

Re: People who've had false knock..
 

Any one know how to determine if a knock filter on the original MEMCAL is faulty?

Re: People who've had false knock..
 

Re: People who've had false knock..
 

Is the filter in the MEMCAL or the ECM? All I know for sure at this point is the knock counts are crazy high, but the actual knock is very minimal or non-existent.

Re: People who've had false knock..
 

Re: People who've had false knock..
 

I removed the wire lead connected to Knock Sensor and did some more data logging. Tuner Pro showed zero knock counts, so would that mean my MEMCAL filter is okay? What exactly does the filter do????

Re: People who've had false knock..
 

I have a question. The plugs that are installed on the car (1991 350 TPI) are NGK UR45GP (0.060 gap) when I believe they should be NGK UR4GP (0.040 gap). All of the specs are the same between the plugs minus the preset gap from what I can see online. I pulled a plug and it's gapped at 0.050-0.055. Would this gap be enough to cause a spark knock???????