Thread: The last piece to the puzzle...

I'm 100% convinced my car is running knock free (with the occasional 0.5* blips of PT KR when leaning heavy into the throttle with the TCC locked). Only, it doesn't seem to think so.

As soon as I hit PE, be it by gently rolling in to the throttle or straight up flooring it, 9* of KR shows up and begins to recover with no more spikes. I can recover before I get out of 1st and see no knock through 2nd and a good ways into 3rd (limited by running room and the size of my cajones). No matter how I try to do it hitting PE gives me 9* of KR to start with. I am now certain it is something tune related, due to how it appears only right then.

I'm going to dig through the PCM and see if I can find what is causing this. If that fails, I'm just going to increase the KR recovery rate since I know it isn't real knock and that the car is running great.

Any suggestions would be helpful.

for a spike like that, its got to be your exhaust hitting something.

that is, if youre convinced the tune is spot on.

But if my exhaust was hitting something, it wouldn't occur at the exact TPS value every time that my PE mode is set to engage. If I set PE to 30%, it happens at 30%. Set it to 60%, it happens at 60%. That correlation is what leads me to believe it is false KR generated by something in the PCM. Once it recovers it runs like a champ.

Also, it isn't just me. Whitelightnin04MC is having the same issue and he used a ZZP file as his base. I used a stock file to start with. Our mod lists are similar.

hm...weird. i have no suggestions anymore. good luck?

Originally Posted by Bio248

hm...weird. i have no suggestions anymore. good luck?

Thanks anyway. I'm open to all suggestions because I'm hoping we're missing something.

ok so here is a question for you. can you more or less get rid of the knock sensors? or do you have to have them? for all you folks that continusly monitor your stuff, why do you need it if you are always looking at it.

If you get rid of your knock sensors, the PCM won't be able to detect knock and compensate. Thus, the engine will be damaged (chipped piston, damaged rod bearings, etc).

Knock is going to happen at some point or another. I'd rather the PCM be able to compensate than the engine blow up. Removing the knock sensors is like taking the "Check Engine Light" out of your dash and ignoring the problem. Nothing changed, just you removed how the car can notify you of something and possibly avoid damage.

yea, but they have been running s/c and other cars without them for years without the help of a computer. anybody that still uses a dist and carb can atest to that. personally I seldom had problems of the such. I know its there for a reason, but I still cant understand why you would keep them once you start getting into the street rod side of mods.
Im not trying to be facious honest.

True, but carb'd engines weren't pushed to the limit in regards to spark advance like electronically controlled engines are. EFI engines are more powerful than carb'd for a reason, mostly because they can push the envelope on spark advance due to the safety net provided by knock sensors and the quick reaction time of a computer.

All it takes is under a second of uncontrolled knock and our engines are toast.

ok now I got the answer that sent the signal to the little light bulb above my head.

Back to your regularly scheduled tuning thread.

I've got an idea, but it's got to wait. I was working a lot this weekend and with low manning won't have a day off to compensate. Maybe this weekend I can try out some of these ideas.

My guess would be that you are running rich or lean when you hit PE. Do you have a WB?

Originally Posted by Zef_66

My guess would be that you are running rich or lean when you hit PE. Do you have a WB?

Not yet unfortunately. I'm going to play with PE and see what happens. I doubt it's lean since it isn't knocking as I gently roll into it, but as soon as PE hits (and O2s go up) it gets that ~9* spike.

My other idea is the EGR valve. When PE engages its supposed to shut. I'm wondering if it's dirty or faulty and this shutting motion is causing a "ping" one of the knock sensors is picking up. Gotta unplug it and see what happens.

Originally Posted by Sabrewings

Not yet unfortunately. I'm going to play with PE and see what happens. I doubt it's lean since it isn't knocking as I gently roll into it, but as soon as PE hits (and O2s go up) it gets that ~9* spike.

My other idea is the EGR valve. When PE engages its supposed to shut. I'm wondering if it's dirty or faulty and this shutting motion is causing a "ping" one of the knock sensors is picking up. Gotta unplug it and see what happens.

Unplugging the EGR won't necessarily help if the valve is stuck. Removing it would be your best option here.

I didn't say it was stuck. I said the sudden shutting of it might be causing a vibration (ping) the knock sensors are picking up. Unplugging it would keep it from moving, thus helping me in my troubleshooting.

Unplugging the EGR didn't do anything. I knew it was a long shot.

Back to crawling through my file and my scans for anything. If I don't find something new to try, I'm increasing the KR recovery rate.

Finally solved. WOT on the L36 file is just too damn high. I found a happy medium around 18-19*. Stock file commands 24*. O2s are in the 880-890 range.

..you were running 24* of WOT timing? with a mild setup i dont think you could ever run that high.