Intermitent bad knock

[RealMcCoy]

When the conditions are right, usually around 13-14 psi, hot temps, under a hard pull, I'll suddenly get horrendous yank all your timing out knock.. When it happens, you may as well shut it down and cruise it home, because it's not going to stop.. If you shift gears, or get back in the throttle, the knock is immediately back, and it doesn't matter how much timing it pulls..

The car is pretty stock, just gutted precats, open element air filter, manual boost controller, and more fuel pump than the stock injectors could ever use..

The car still has the stock heat range platinum plugs.. My current theory is that they're going glow plug on me. Has anyone had this happen with a basically stock car at these boost levels? Anyone fixed a problem like this with colder plugs?

[lawdogg]

Are they NGK plugs? At .030 - .040 gap?

What's your timing & AFR under knock situations?

[RealMcCoy]

Originally Posted by lawdogg

Are they NGK plugs? At .030 - .040 gap?

What's your timing & AFR under knock situations?

Yes NGK plugs. It's been a few months, but I think I gapped them at .035

Stock O2s parked on .95

Stock timing map base at 5 deg. I wasn't kidding when I said it would yank all the timing.. I've seen it at -2 advance with no change in knock count.

Thanks,

Larry

[lawdogg]

Huh. How much knock? Do you have any logs you can post of this happening?

[RealMcCoy]

Originally Posted by lawdogg

Huh. How much knock? Do you have any logs you can post of this happening?

When it happens, the knock count will be 22-28. I normally don't see anything over 6-8.

I could post some logs tonight after work..

[RealMcCoy]

Well I was having some issues with my logger talking to my PC.. Got that solved. Then I was seeing some weirdness in my fuel trims and O2 readings. Found a bad fuel pressure regulator.

Got it back to a normal state of driving me nuts now...

Here's a couple of logs. I wasn't logging very many parameters in these trying to keep the refresh rate up, but they do prove what's happening..

It seems MMCd tools was designed for the original version.. I'm using 1.8, and the timing is correct on my palm, but reports 10 deg higher in the Exel file, so you have to subtract 10 deg from these logs to get correct timing.

I've found that if I roll on the throttle easy in second, and granny shift to third, it pulls hard with little knock all the way through. If I hammer down in first, and bang shifts like you're trying to get somewhere, You get crazy knock as soon as you shift, and it won't go away until you get off the throttle.

[RealMcCoy]

OK, Here's some zipped versions of the Exel files. (CSVs Don't look very organized)

I'm not sure if it's a software glitch or a real problem, but I noticed that I'm getting some tach variations in the log. there are several instances where the RPMs drop a couple hundred when I was under full power acceleration. I think I'll break out the lab scope and see if I have a primary ignition issue.

[ZephTheChef]

Motor mounts/other phantom knock?

[RealMcCoy]

Originally Posted by ZephTheChef

Motor mounts/other phantom knock?

That's a possibility that I'm entertaining, but I don't have any real evidence either way.. It would seem that motor mounts would show up in low gear the most.. They all looked good when I had the motor and trans out, with the exception of the rear mount which I replaced with new..

My next step is to get a lab scope hooked up to it, and look at the tach and knock signals for evidence of interference, or some recognizable pattern..