some knock and fuel trim Q's

[cyberslug]

Hey guys,
In general my Talon is doing well but there is still cpl of things that are nagging me.

Fuel trims, are 80-85% at idle. They move around lots, seem to go up in cruise and back down at idle. Here's the real kicker, I put my headlights on they jump to 103%. I have no significant leaks. ~18-20HG vac at idle, TB leaks a little but I can't fixed that until I get a new non-'90 TB. Also, O2's are fine, definatly closed loop. I get idle surge a little w/o the headlights too. Just wierd....

Knock, since the new head and related work, I have 0 knock when I get on it. I can stomp on it, spool up, get full timing all that good stuff. But when I'm cruising, especially when cold I get TONS of knock. Like 2nd gear, barely any throttle, 43counts. Lots from a stop too, almost like the drivetrain is cold. Seems to fade off after driving for 15mins or so. I did go 1 step colder on plugs, ngk 7's can this cause it?

When i put these 2 problems together in my mind I think injectors. Either a clogged one or something voltage related. I heard that the injector voltage is based on the battery, is that right? My battery is nothing special (sears diehard), but seems to be fine. No starting issues or anything. Maybe ECU related? Can you guys give me some stuff to check?

Thanks much!

For the record, pretty dang stock...
KN filter, unhacked MAS
2.5" exhuast w/big cat
Stock boost
NGK wires, 7es plugs
EGR blockoff
500Miles on rebuilt head, MLS gasket
New knock sensor (helped LOTS)
Still have some lifter ticks, need to have Jack replace them.
A/C, PS pulled
I think that's everything relevant

[yokotabrat]

Injector deadtime is based on battery voltage, however since you are relatively stock and you have an unhacked MAS, I kind of doubt you're deadtime is off. I think the key would be to get your idle surge figured out first since it sounds like the isc can't compensate when the headlights are off. Have you adjusted the biss per the manual? That'll center the isc range and provide full adjustment capability of the isc. I'd also check the isc coil impedances to see if everything is okay there. Maybe if the idle surge is fixed, the low fuel trim will fix itself.

For the knock, I'd start with some high octane fuel to see if the knock goes away. If it doesn't then I'd start looking for mechanical noises. The lifters are a very likely candidate and can cause all sorts of weird partial throttle knock.

Hope this helps.

[cyberslug]

BISS fixed the idle surge, it's sticks at 750 no matter what now. Fuel trims didn't really move though.

[yokotabrat]

Hmm, well according to my notes, deadtime increases as the battery voltage goes lower. That seems opposite of what's happening on your car (if my assumptions are correct). When you turn the headlights on, the fuel trim goes higher indicating you're leaning out. Usually, when the headlights go on, the battery voltage will drop slightly which should cause you to go richer if you go to the next lower table value in the deadtime map. According to the map, though, that doesn't happen until about 11.68V. I just don't know if it interpolates between the values.

Can you log battery voltage before/after you turn the headlights on?

Also, I forgot to clarify earlier, which trims are moving around? Is it only the low trim that's moving a lot? What are the mid and high trims sitting at?