Ok, first I have searched and read most of the numerous threads on this, just wanted some other opinions on this particular situation.

I ran my car (95 formula) at the track for the first time today and did kind of bad (15.2 @ 92). Wasn't sure what it was at first but then I did a few logs and saw I had 12 degrees of KR at wot.

It gets especially bad past 5500. I know that headers/cam etc. can cause false knock but I wanted to know if anyone had experienced it on a more stock car (my car is stock except for flowmaster 80 series exhaust and a tune, nothing ignition related in the tune).

I think that the knock is false for several reasons, one is that I don't hear or feel anything strange when this occurs. There is no stumble, miss, etc. and the car feels like it's running good, just doesn't pull very hard (obviously due to that much timing loss). Also it appears that the knock sensor continues to detect knock even with huge amounts of timing being pulled. If it was real knock, wouldn't this correct it?

Here is a relevant portion of the log so you can see what I mean.

AFGS LO2 RO2 TPS RPM spd MAP adv ret knock count
227.11 910 919 100 5600 91 93.7 28 12 7571
235.23 901 928 100 5525 92 92.3 29 10 7609
232.47 906 910 100 5725 93 91.9 33 6.8 7609
231.09 910 906 100 5675 93 94.9 28 12 8649
234.01 906 892 100 5725 93 93.7 28 12 9903
229.96 910 901 100 4325 95 94.5 29 10 10178

Also there are large sections of the log where the knock count does not increase but there is still retard.

One thing I wasn't sure about, the previous owner apparently ran 87 gas in the car (yeah I know), but they drove it infrequently and never raced it. I got all of that out and filled it up with 93. Could this have put the computer into the low octane mode and could that be causing it to do this? I know the low octane mode uses a different timing table but I wasn't sure if it affected knock sensitivity.

Oh and I plan on running some race gas and seeing if that changes anything but it may be a week or two before that happens.

 

I had the same problem, but mine would occur at 3800-4300rpm, even on a stock tune. I did all the troubleshooting and finally dialed the timing WAY back in that block until it went away. Have you tried throwing in a stock tune and making a WOT log or 2 to see what it does? Im no computer genious when it comes to tuning and looking at logs, but I could take a look at yours if you want. benitez2367@yahoo.com

 

All of the timing is still stock. The only thing different in the tune is some stuff like fan settings and tranny shift points.

I'm basically just trying to figure out what the chances are that it is real knock. If it's not I'm just going to reduce the max knock above a certain rpm, because there's no reason to reduce timing if it's not really there. I'm just not sure why if it was real knock 12 degrees of retard would not correct it.

 

any other ideas?

 

Mine was getting about 8-10 degrees when I took it to the track for the first and only time so far. A while back ago when I put it on a scan tool for the first time (maybe 3 years ago) it was getting alot of knock going from highway cruise to accelleration...I then took out several degrees of timing and cured it.
But at the track at WOT conditions it could be a number of things....weak fuel pump, fouled spark plugs, toasted wires, weak coil, or worn opti.
My fuel pump was still flowing 42# at WOT which is what the pressure should be with the vac line disconnected from the regulator, but the flow of the pump could be suffering...so with that, I just changed the pump this weekend, and put in a new coil.
Going to be putting on headers in the next few weeks, and will be changing the factory original 85k mile plugs and wires too...I hope that will cure it.
I was planning on doing all of these things anyway so the knock didn't really concern me too much, knowing it had a lot of miles on the plugs/coil/wires/pump. If it continues to do, and you don't want to replace things just yet, fill the tank with some unleaded 104 race fuel and see if the knock remains. The higher octane may be enough to mask a weak pump but may not the other issues....the pump is the hardest to replace anyway so thats a last resort. If your plugs/wires/ and coil have alot of miles on them, I'd replace them.
My motor BTW was 100% stock to start with, nothing but the battery and belt had been replaced.

 

His O2's don't indicate its running lean. Recognizing the limits of the stock O2 sensors, its not certain, but likely.

You won't "hear" anything when you have knock retard. The knock sensor hears it before you can, and pulls the timing. You are not likely to hear anything, or at most a little "rattle" when the knock first hits. When it detects knock, the PCM starts pulling timing quickly until the knock disappears, then gradually puts the timing back in, until it hears more. Then the cycle starts all over again.

You won't necessarily feel a stumble or a miss, because the knock retard does not cause those. It pulls timing and power drops. It will feel like a dog. If the retard it there all the time, it will just be slow, not a surging feel.

Its entirely possible for retard to be present without the knock count going up. Its also possible for the knock count to go up without causing retard.

You indicate you have a "tune", but then say the timing table is stock. The PCM is attempting to set advance in the range of 39-40deg, but its pulling 10-12deg, so you're only seeing 28deg. I don't have a stock timing table in front of me, but is the stock table that high at 5,500rpm/93kPa?

 

No stock is 35 deg in that range. What could be causing it to run 4 more degrees?

I suppose I could try reducing it 4 deg and see if that makes it actually 35.

 

Almost forgot, I had a PCM go bad once and the only thing it did was create a false knock reading, it was taking out 4 degrees just at cruise and 10-12 on accelleration. Replaced the entire PCM and no more knock....I guess it could have been a bad knock module in the PCM as well that could have been replaced separately.

 

Ok, got some more info here.

It appears to be speed related as well.

Notice that the log portion I posted starts at 91 mph. I did some more logs and I only get that bad retard at WOT starting around that speed. There are occasionally a few knock events but the retard recovers and goes to zero. Once I get around 90 mph I get this horrible consistent max retard and the knock count continues to increase even with max amount of retard.

So it appears to be either related to speed or rpm over about 5500.

 

My stock table for the 95 has timing at 30 degrees for anything over 90 KPA MAP reading. You may not see the exact timing thats in the table due to op temps, coolant temp and maybe some other variables.
I'd say, reduce the timing in the upper end by a few degrees. Sometimes having only a degree or two more than the octane/compression can handle will cause 4x the knock retard.
Maybe the gas quality has changed significantly since the "tune" was done. Winter gas is lower quality to begin with. As a test, you can always add a few gallons of 101 or 103 unleaded race fuel to a few gallons that are already in the tank and see if the knock goes away. If it doesn't effect it, then it may be false knock. But then again, since it begins to occur when the engine begins to loose the load against it...which also causes the motor to not tolerate more timing as well.

 

I don't know if this is your problem, but a carbon tracked Opti-Spark cap was causing massive knock retard on mine.

The cap had a track that was causing the next cylinder in the firing sequence to fire prematurely.
Even on light acceleration, there was massive retard.

Tom Piper

 

I have seen a 95 and a 97 knock at higher rpm's with the stock table. My stock table showed 33 at 100kpa and 35 and 90 and 95KPA.

Currently, I like my timing table set at 30deg for 90,95,100kpa at 2800 all the way up.

The computer slowly adds more timing up to about a total of 34 by 5000 or so.