Thread: Cruise KR, and a lot of it.

Originally Posted by J57ltr

I actually meant knock sensors... My bad


the gauge reads -* as in degrees before, is this correct? I've never used one of those. But if that is the way it reads then that is low timing for sure. Mine would go to 0 and 15*adtc. It's done 10* atdc but I have some other issue as well. Mine was doing just that before I changed the knock sensors but it even did it with that other computer so I think in my case it was both the PCM and knock sensor. Did it just all of a sudden happen or progressively over time? Did it happen right after a tune?

Jeff

I use the symbol * to represent Degrees. Knock Retard and Timing are both read in Degrees. Mine could be a combination of both, like you stated. Knock Sensors and a PCM issue. This all of sudden happened a few months ago, but I never really cared about it because Cruise Timing isn't "detrimental" to an engine like WOT KR is. But it has gotten worse over time, and now when I'm cruising anywhere, my KR is pegged at 14.9* KR and the car is pulling all my timing, and causing me to average 14 MPG. And this can't keep going on, as the issue needs to get fixed since I'm wasting my money on fuel every 4 days. Averaging $40 every 3-4 days.

Originally Posted by J57ltr

I think there is something in the program's get (either stock or aftermarket) that causes it to do so without the knock sensors connected. Like a default table of sorts.

Edit: remember that I am guessing on this as I have no GM program experience.

Jeff

Your guess is as good as mine, at this point. Luckily, I do have a ZZP Canned tune for my car laying around in my garage. It's a **** tune as my LTFTs are -21 +/- while driving, but it might give me an idea if the KR is related to a bad PCM or not. I could try switching the PCM's and plugging my Knock Sensors back in, and seeing what it does.

Originally Posted by bandook

I'll take a look at the tables in Tiny Tuner, but who knows if there is a hidden table that is causing this. There are definitely several tables that modify spark, but for your scanner to show KR I would think that could only come from one place-knock sensor. Its like having the MAF unplugged but still reading MAF frequency changes. Doesn't make sense to me.

Exactly. My only thought at this point is it's PCM related or possibly a combination of both a bad PCM in that regards and faulty Knock Sensor(s). Like I mentioned above ^ I do have a spare ZZP Canned Tune PCM in my garage I will switch out and see what the car does. Could also try putting my newer Denso o2 sensor back in as well.

Yeah, I may be lookingbat it wrong. When your AF gauge reads -14, I'm viewing that as -14 atdc. For instance, my car idles around 24°. Would yours normally idle at -24 according to your aeroforce?

My car idles at -22*, so I'm assuming that's 22 degrees below top dead center, if I'm correct? So when watching timing, as mine is read in negative values, that should stand for "X" degrees below TDC.

Yeah, makes sense now. I would definitely get that other pcm in and compare. The tune might suck but you should get better mpg with negative trims than you would with crap timing.

I'll swap PCMs, and plug both knock sensors in tomorrow and let you know the results.

Curious though, if it is the rear knock sensor, how do you get to it? It's on a tight spot looking directly up at, can't fit a wrench there, I wouldn't think.

Just so you know, all 97 PCM's read timing backwards.

All negative timing numbers are really positive. But that still doesnt change the spot where it asking for timing, it's still 22º before tdc.

From Hp Tuners.

Converting negative reported timing advance to positive
Application: GM V6 based vehicles

For many late model GM V6 based vehicles (those derived from the 3800 Series II platform) the factory computer will report positive timing as a negative number.

The way I understand everything is that it's always the advacned timing before top dead center.

If you had a spare pcm laying around and still having issues after all that test work , I would spend the 5 minutes swaping the computers. It sure as hell beats the labor involved doing a read knock sensor and what ever else.

Now we have another issue on our hands. I won't create another thread, so I'll just post here. Here are my steps:

-Plugged both Knock sensors back in.
-Removed both 7mm bolts holding the PCM Wiring Harness into the PCM
-Replcaed PCM with spare ZZP one I had in my garage
-Went to start car, crank no start.

-Put "old" PCM back in, crank no start again.
-Turned ignition on, fuel pump is not running or injectors. Car is getting no fuel.
-Checked Fuel Pump Fuse and IGN1 fuse, both good.
-Can hear fuel pump relay "click" when ignition is turned on.

-Removed rear seat
-Removed fuel door cover, unplugged fuel pump connector, turned ignition on and checked GRAY and BLACK wires (Power/Ground) for fuel pump motor feed with a voltmeter, and no voltage.

I'm stumped. Why in the hell is the fuel system not running when all I did was replace the PCM. It's a '97 and these cars don't need a CASE learn because of the Knock Module. Fuses look good (unless I'm missing one). Just checked the 15A fuel pump fuse in engine bay fuse block.

Only thing I can think of, is pin 55 on the PCM (I think) is for the Theft Deterrent Fuel Enable Signal. For some reason the car is detecting theft, and shutting down the fuel system?

Maybe just leave the key in the ignition for 10 minutes?

Ignition on for 10 minutes?

To "learn" the new PCM?

What about unplugging the battery for 10 minutes?

Originally Posted by J57ltr

I don't know about the earlier cars but the DIC on my 05' will say "Starting disabled due to theft system" or worded very close to that. I haven't swapped in my old PCM because it pulls full lean on me so I've only the experience of replacing 1 PCM but the starter didn't even try to turn over when I switched PCM's until I went through the learn procedure. Hearing the relay click is odd unless there is another relay that kills power to it. Do you have a meter?

Jeff

Unless I'm hearing another relay click.

Yes I have a multimeter.