Holley EFI Tuning Problems
 

I am having a problem with my Terminator EFI system. I haven't been getting much help from the Holley Fourms - a couple of suggestions but no solution to my problem yet.

Overall, the car runs well. It pulls hard an idles well when the idle spark is turned on. There is an occasional low RPM bog (at or off idle) that makes the car want to stumble. When cruising or accelerating, it runs great.

Right now it idles pretty well. Right around 900 RPM. However, if I try to rev the motor without a load, the RPMs will hunt/bounce up and down and never settle on a steady number. AFR goes full rich to full lean (10-28) during this hunting. At idle, AFR varies from 12-14 with a goal of 13.5. If I turn off Idle Spark control or turn on Static Timing, it will hunt at idle too.

I'm not sure where the problem is. Holley forums (Danny mostly) thinks I am either too lean, have a failing WBO2 sensor, or an exhaust leak. I'm not sure any of these are my problem.

Lean?: the Learn table is removing fuel, anywhere from 2-5% in these areas. Learn is active during these bouncing fluctuations.

WBO2 failing?: This has been happening for a while. I replaced the WBO2 sensor a few months ago. This was happening before the replacement and continues to happen despite the new sensor. I don't want to replace another $100 sensor and have it also not be the solution.

Exhaust Leak?: I resealed everything from the heads back. Still bounces.

There is one suggestion that I may be having a misfire causing a false lean spike, then overcompensation by the ECU causing a rich condition which causes another misfire. Not sure how to test that. I'm getting spark in all 8 as verified by a timing light.

If anyone is willing to look, here is my Global Folder (datalogs included inside ZIP: Click Here

Here is a picture of the log while hunting (if it will load, Click Here if it doesn't):

https://www.dropbox.com/s/rggvgykj3z...ngRPM.jpg?dl=0

If it matters, I have the following:
408 stroker
Cam 230/236 at .050
MSD 8452 with Ford brand Ignition module
MSD wires, Champion plugs recommended by AFR
AFR 195 heads
Mallory HiFire 6853M ignition box (MSD 6AL copy)
Mallory 30440 ignition coil

Any thoughts on what's happening?

Thanks in advance, Tom

Where is the O2 sensor mounted.

Passenger side pipe approx 8 inches after the collector.

It's probably too far back. I ended up moving mine to one cylinder header because someone had already put a port there. After that the idle ran lots better. I was told by the Accel system guys that the low volume at idle allowed some air back into the pipe and caused the o2 sensor to get false readings.

I have read stories about leaks at the collector causing problems if the O2 is after. I know nothing I like to read about technical things and that one thing has been the source of some problems. Take it with a grain of salt.

In the drop box graphic, it looks to me like it's so rich it's missing and reading lean. Here's one of the areas where auto tuning can't work. It sees a rich misfire as too lean. Having the O2 so far down the line makes it react slower and sluggishly. Manually pull about 20% of the fuel from the offending part of the fuel table. Just mess with the 9 to 12 cells the oscillation is happening in. if it fixes it, manually smooth the table around it.

I've found the area below 2000 RPM is the hardest to tune. Especially where you're just coming back onto the throttle in second gear after a right turn or something where you lug down a little.

If you do eventually give up (not at all suggesting you do) before you scrap the hardware, get a megasquirt. They have the good sense to not let the auto tune do anything below 2000 RPM without changing the VEAL (VE AnaLyze, their version of autotune) default settings.

If you can, it's best to turn off all closed loop correction systems until you get it stable and running good. Closed loop feedback systems like AFR corrections, closed loop idle control and idle advance can all wreak havoc trying to correct for an off tune. Double that with a lopey cammed V8. They should only be enabled after you have a pretty good running engine to make it perfect and able to correct for changing constants like alternator load, temp and altitude.

Didn't you take it and get it professionally tuned?

Stick with it. You'll get it figured out.