Background:

Took a long 400 mile trip down to the southern tip of IL this weekend. Halfway through the trip I tried some new injector latencies to see if I could fight some cold-start bogging problems I've been having related to a hard intake pipe change.

Everything was fine for most of the trip down and while there. On the way back, the first station I stopped at seemed like nothing was out of the ordinary. Did the E85 fill up and it was the same station I had been to just 2 days earlier.

After cruising 80-90mph for about 50 miles I started getting periods where on perfectly flat ground, no throttle modulation I would see 1 or two low knock light flashes, then a CRAZY amount of high knock light flashes. I finally caught a log of it below.

My fuel trims were on the lower side since the latency change, but not yet maxed. AFR looked to be decent when this was happening. I can't think it was bad gas since I had been fine for the whole weekend from the same station right before this. My timing isn't crazy in this area and wasn't bouncing around near the area where the knock would occur (that was my next thought). There was no audible knock, but IMO the car is rather loud from wind noise at this speed even though my exhaust is fairly quiet.

Then, at my next stop I saw the log and almost flipped.

Log: http://thefrost.net/randomfiles/tuni...crazyknock.csv



The same thing happened a few more times the rest of the way home, but traffic was building a bit at that point. Still no audible knock, still very light if any throttle modulation. Always right around 3600 RPM or 3900RPM.


The only thing I can think is it is possibly related to the way tephramod V6 handles octane value interpolation now and was making the ECU go crazy. Has anyone seen their octane level drop on a v6+ rom?

 

i have never seen anything like this before.

 

Its in the 60-80 cells similiar to my midrange knock... Granted I don't drive 400 miles, but you read in my other thread that it would happen once on every 45 mile trip. I am running a V5.1 and V6 combined map from all the compiling of xml's I have done for the 94170015 rom. Just wondering if you think it could be something similiar?

But very random none the less, and very interesteing. Subscribed for the solution, if it might be relative to me.

 

Yup, I was going to cross-link your post. It reminded me to post this.
https://www.evolutionm.net/forums/ec...rtup-help.html

Fortunately for you there isn't constant 36 counts in your log!

 

Interesting. It didnt do this at all on the earlier versions 5.x? If I didnt know better I'd say you have all the classic symptoms of balance shaft delete instigated knock.

 

Its right at the edge of transition between the low and high filter in the knock control which is also odd. Since its vacuum and on e85 I would say numb the sensor if you want to keep V6 or switch to an earlier version if that cures it/never happened.

 

Yeah, for now I'm going to burn off this tank and see if I can get it to happen again. (on this tank or another one from my regular trusty station). I haven't had a chance to drive her since I got home, but I usually do 50 miles to work 3x / week so hopefully I should get a chance to see what was going on.

I do get random small counts here and there at light throttle every couple of days, but changing the latencies probably threw things off enough to toss a couple of extra ones. Thats what is making me think that it might be going into some sort of error routine for the octane value since the 4 count looks like it spiraled it off into the craziness.

I'm still on the stock timing belt and balance shafts, but I haven't touched the knock filters at all. I'm running S1s with an AMS front lower mount, so things are a bit rougher at times. If it keeps happening I'll try to dumb them down a bit right there and see what happens. I had considered it before since I was getting some spool knock, but pulling a degree or two cured it so I hadn't touched them yet. The random counts I get DD'ing was having me second guessing weather or not I should decrease the sensitivity slightly, but hadn't been enough cause for concern yet.

 

I'm not sure this is totally relevant, but I actually had to lower timing from my gas map in the 3500ish RPM range to quell knock on E85, which I thought was very weird.
I also believe we may have just hit the switch date to the middle blend E85 gearing up for winter around here in IL. I can't remember the date for sure but I'll go check out my LTFT's for you to see if mine look funny.

 

I wouldn't have thought V6 would have anything todo with it..

my guess is tank of gas, knock sensor on the way out, or something else odd

 

I am currently after this weekend leaning towards maybe a little to agressive boost, and very crappy UTAH 91.

I adjusted maybe 3 cells decreased timing by one point only, and bought gas in another state, and i saw almost 2-3 counts lower of knock on a 3rd gear pulls, but she is still knocking in the high end though.
(Edit: I noticed that the knock in the high end is occuring when the car is in the 5-7k range, it starts to drop load out of the 200's into the 190's and 180's, it's this reverse drop in load that is kinda unsmooth. Not sure how to tune for this type of knock?)

200 + miles of cruising 2.5k rpms ~ 4K rpms, 23 psi max, with 0 knock, on the current settings.

Could be gas related for those of us up north where gas is switched for heating fuel etc, and then the pumps suffer.

Edit:Tephra, do you by chance have a very clean V.6. of the 94170015 rom, that I could try? I will also make a donation later today or in the morning. Paypal right?

 

yeah i got a similar problem with tip in knock.

i would recommend check ur knock sensor, even ur gas, i once got 87 octane instead of 91 octane here in trinidad, then again its a 3rd world country

 

States that have a Fuel Plant of any sort in them, that process diesel or gasoline, get the 2nd of the pickings and get worse gas at the pump then those states that the gas is trucked or shipped too...lol.

On the knock sensor, is that something we should check? What do those usually run for replacement?