Tuning question

[discostu]

exactly the reason i disabled open loop mode.. mine would run in the 6.x AFR range and die constantly untill closed loop would come in and it would run great.

So you run closed loop as soon as you fire your engine? Even with a cold O2 sensor that isn't giving a proper O2 reading?

Why not just adjust the open loop AFR's?

[Superdave]

nothing worked at the time.. i know a bit more now, maybe i'll work on it sometime.


my heated wideband takes like 15 sec to warm up, the BLM's go crazy in those 15 sec but looking at the big picture the car never stalls.

[torq455]

even with my small mods, my cold AFR needed at least .5 richer. my 02 was under 100 mV. now it's up in the 900s.

[discostu]

New question. I've got a hunting idle when warmed up, over about a + or - 75 rpm range surrounding the desired idle. I'm thinking that it's because of the idle spark and fuel routines. The idle spark goes up and down over about a 6* range from 16-22 or so, and injector PW also has a .3 mSec range of about 1.3-1.6 mSec. Does anyone else have this problem using BFUZ code?

Also sometimes (not very often) the idle drops quite low, like 300-600 below the commanded idle (800), then the stall saver kicks in and it revs up to like 1500-2000 for about 10 seconds before the IAC steps are decayed.

Is there a way you can not use the idle spark and fuel routines, like open loop idle or something? Is anyone doing anything else with their idle that might help me?

If anyone was going to ask, I just did a complete tune up with new plugs, wires, PCV valve, oil change and carb cleaned the plenum and tb. I also put Seafoam in my crankcase, fuel and intake via vacuum line (1/3 can for each). Man did it smoke for a long time (like 15 minutes) after the seafoam in the intake lol.

[torq455]

i have the BFAH withthe same problem. the timing and IPW vary simple because of the varying rpm and kpa values. you have either had the battery disconnected, or just burned/uploaded a new .bin. the ecm has to learn how to idle either way. i'd suggest performing an idle relearn, but when you are pretty much done tuning. i was told this by a GM tech: disconnect battery for a min. of 30 seconds, reconnect, with ALL electrical accessories/anything off and the engine cold, start the engine. if it dies just turn the key again-don't do anything else. then let it warm up until the thermostat opens, shut it off for no less than 10 seconds, restart and put it in drive with the E-brake on. let it idle in drive for no less than 5 minutes and you're good to go.

that method has never failed me. there are other versions too, but i know this one works.

[Superdave]

check the idle over and underspeed spark advance correction VS RPM error.. some tweaking there usually helps.

It's pretty normal for MPFI engines to hunt a little at idle, that's why SFI OBD2 engines run so much smoother.. better injector controll under 2K RPM.

[discostu]

check the idle over and underspeed spark advance correction VS RPM error.. some tweaking there usually helps.

It's pretty normal for MPFI engines to hunt a little at idle, that's why SFI OBD2 engines run so much smoother.. better injector controll under 2K RPM.

I suppose that makes sense. Low rpms > batch fire
I did check the over/underspeed advance tables. I tried lowering them a bit before, but I'm not sure it had much effect. Maybe I'll work on them a bit more.

What about open loop idle, or lowering the settings so I never enter idle spark? Anyone ever tried anything like that?

[Superdave]

what does your integrator do at idle.. swing around alot or does it stay pretty decent?

I wouldn't disable idle spark, but you could always give it a try and see what happens..

Set "Idle Spark Disable TPS Threshold" to 0 % TPS.. that should do it.

Also, if it's the fueling side causing the hunting idle try messing with the "Idle rich/lean o2 Threshold" it's set to 0 in the 5 speed bins but .163 in the autos..

[discostu]

The INT is very steady at idle, barely swings at all. Idle BLMs are between 124-128. I haven't really played with the O2 settings yet. I haven't gotten my heated O2 installed yet and I have no idea how many miles are on this old 1 wire O2 that's currently installed.

Something I did do in my tuning was lower my BPC from 224 to 197. This is on a bone stock 3.1L. I laughed the first time I saw how rich it was with the stock BFUZ tune, like low 100 BLMs, pretty much everywhere. It's still rich in some areas too.

I also added 3* of timing to the entire timing table, then smoothed the hell out of it. It feels more responsive and less jerky, and I've never seen a single knock count. There's tons of areas in the stock bin that have 5-7* differences only 1 cell apart.

[Superdave]

weird.. my old 93Z ran BFUZ and the BLM's stayed around 128 most of the time.. Maybe you're at a different altitude then I am.. lol

[discostu]

Maybe. I'm in Edmonton, AB. The altitude is 2200 ft and baro is usually 93-95 kpa.

[torq455]

mine ran rich too. (BFAZ) was between 105-115 BLM, and that's with all of my current mods! yeah, a better tune and 2-3* more timing really helped the responsiveness. my alt. is 1200 ft and baro is 90-92 kpa. i also added 4* of timing in the 600-1000 rpm, 20-100 kpa ranges. that really made the engine idle smooth.