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Discussion Starter · #1 ·
Hey Guys,

Question for anyone who is familiar with our knock control system. I think my car is knocking but it does not register with the ECU. I have basically a stock 88 GT with Boost controller, blaster coil, Adam chip. I now have a high-res voltmeter set up to monitor the singal wire from the Knock-module to the ECU. Under no conditions does the signal ever go below 4 volts. The facotry manual states that this signal should be 1.6-3.3v under "knock" conditions. I have tried knocking on the engine lift point with a hammer per the manual, the knock signal voltage to the ECU does not fluctuate at all, still above 4v.

I have always had problems with stuttering/severe-knock type of behavior over 9-10psi of boost, that usually goes away if I replace the plugs, and then comes back a few thousand miles later. I've tried every plug out there. Running stock style, 1-heat range colder NGK's now. Ignition base timing is set to stock per the manual.

I find it hard to believe that I never get any knock under any conditions. Anyone else played with or familiar with the knock module behavior?

Drew 88GT
 

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Discussion Starter · #2 ·
Update

Update to my stuttering problems...I disconnected my Blaster coil and tested it with the volt meter, looked just fine. I noticed however that the terminals on the distributor coil-wire side, and in the coil itself were a bit corroded. I cleaned those up and plugged the coil wire back in(the Mazda/NGK wire to the Blaster coil just doesn't seem to fit *quite* right). Now most of the stuttering is gone, just a bit every so often under boost now. I'm sure yet another set of new ZFR7A11's will solve that problem(It's good I stocked up on'em!). I ordered a new cap and rotor and wires as well.

I don't know about anyone else but my car seems to be extremely sensetive to ignition system health, and it needs new plugs about every 10k miles. Other than that I guess I will just have to trust the knock module reporting no knock. The EGT's look good, I guess it's time to put in the Walbro and crank the boost up a little more.

Drew 88GT
 

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it's probably not knocking. Sounds like your blowing out the spark and you need to decrease your plug gap. Don't run the .044 spec on a boosted car. Run a .032 and you should get rid of that miss.

BTW, a knock event is about .5 mS long if i remember what my oscilliscope was reading when i was tuning. A regular meter will have trouble catching an event that short.
 

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Discussion Starter · #4 ·
Thanks for the tips Zombie, I think I gapped the plugs at .036 last I had them out but I'll squeeze them down a bit more and see how that does.

Drew 88GT
 
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