I did a search on this but could not find this specific problem discussed.

I have been tuning an ANLU VE map for my 350 TBI w/ vortec heads (cam, headers, exhaust).

While driving (I drove for 1+ hour), my BLMs are reasonable: 128 +/- 2 or so. After getting back home, I had the car idling while I saved my various Winaldl tables. During this time, I noticed that the BLM at RPM1200-MAP30 (idle RPM-MAP), dropped to 117 (previously at 128 or so).

I looked at the real time WinALDL data and BLM was steady at 111, and the BLM average value (latest readings) kept dropping to reflect this.

My original chip was an AXKW. I transferred some settings from the AXKW to the ANLU to help idle quality (decreased idle to ~1000 RPM). Thank for your guidance, RBob!

Could this be an IAC settings problem or could the O2 sensor (it is new) not be giving good readings at idle for some reason?

Just wondering if anyone else besides me has seen BLM register at 128 (or close) while driving and then read rich at sitting idle.
Or if you know of a thread discussing this topic that I missed-

Any help is appreciated.

Thanks,
S-D

 

Weird, Im going to though the same thing today.

My partial throttle driving BLM's are good, 124-129, but when it hits idle they drop to 113 and my Ve table is getting mighty low. I guess I'll keep dropping it but I dont know how far I want to go.

 

Hey Chuck-
After identifying the problem, I did the round-robin- I lowered my VE table to accomodate the rich idle condition. Idle was OK, but when driving, that cell registered a lean condition.

I was like, "Damn! That makes me want to do a long smokey burnout!" So I did, but it didn't really help anything.

So I changed it back and wound up with my original condition (rich idle, normal when driving).
That is what made me wonder if maybe at idle the O2 sensor is not giving accurate info and is causing the ecm to compensate needlessly. Not sure on that.

I searched using "BLM" AND "rich" AND "lean" AND "idle" (all together) but couldn't find this specific problem discussed.

S-D

 

I changed my cells in table 2 for 400 and 800 rpm to lean out across the board and that brought blm's up to 118 at idle, but then at cruise my blms were in the 130's, so then I put the table back to the way it was and changed fuel table 1 some more and Im back to 112, lol. Man its one step forward and 2 back.

At least the burn out cleared your head

 

i also have this problem

 

hmmm... It could possibly be due to exaust reversion if you have a hot cam. I hear that can have an effect on the 02. I had similar problems at very low engine speeds and a cam that i foolishly didnt degree. The cam with a 112 lsa and installed a bit retarded made for lots of rich and lean codes, along with a nasty lope, when the computer tried to idle down to the stock idle speed. Im a real stickler about fuel usage as I do alot of commuting so Ive been able to get blms to 128 at idle and still keep the other blms around 126-130 under most conditions. Dont really see much coupling between different portions of the VE table but on some motors maybe the areas at idle and driving overlap some. and Although the car seems to idle better in gear with a touch more fuel so id be inclined to say leave it if its not effecting the engines idle quality or emmisions. If you can go into winaldl and grab a screen shot of the averaged blms plotted against MAP and RPMs so we can get a look at the areas that are problem spots and maybe zero in on them in the VE table.

Some other things to make sure of is that you dont have any pass. side exaust leaks. At low speeds the pulses will take in alot of air behind them and from experience that really messes stuff up.

 

Chuck. Only change a couple of cells at the map and rpm values that the motor idles at. even with an auto itll only be three-four cells in the main VE table to dial in the VE's for neutral and drive. Changing them 'across the board' will effect areas that the engine traverses over while your driving. Another great way to see where teh engine is at any one time is to open the blm's window in winaldl and observe where the engine is in the table and what the blms are in that spot and adjust accordingly. Again, winaldl comes to the rescue.

 

Funny, my BLMs are all 128, so are my INT! I don't know what you guys are talking about. Oh wait, I forgot, I'm running open loop . That would explain it.
Yeah, when I was in closed loop I would have the same difficulties. I believe you'll find your answer in tuning the spark and AE. If while in steady state with vehicle speed you're getting BLMs around 128 then believe those because you're more likely to be holding a TPS position and not have any kind of de or even DFCO mess things up.
I finally got my laptop working with the usb to serial adaptor so lockers is back up and running. Good thing too because just the other day I was getting a really bad stumble with tip in after the car had warmed up and my open loop AFR table decayed back to stoich values in the mid 14 range. I think it's time to take it to the next level and do some cold tuning with the wideband. Nothing like this crazy cold below freezing Ohio weather to make you want to curl up and never go outside . Takes my car 7 minutes to go from 20 to 130!! It's too cold for a camaro.

 

I'm also in the same boat. My best guess is that with a healthy cam the overlap is just throwing the O2 for loops. There is a way you can run just open loop at idle if you want. You might have to retune a couple times a year because the blm routine won't adjust your idle for the weather. I'll have look through my bin again and see how I accidently envoked this with my 747 ecm.

 

I should make a clarification. Im reffering to averaged blms. If you guys are just looking at the straight up BLMs in the datastream then thats pretty much meaningless as teh blms will fluctuate when the engines operation is transient. When I tune, I try to avoid any highway driving (no HW mode) and try to keep the engine near steady state so the BLMs have meaning. Also try to make sure you get LOTS of data points. The more the better.

 

i will be installing a 226/234 @.05 in spring. would anyone consider running open loop at idle with a spring fall chip/ and a summer chip with that cam? if i recall i saw another post about the ecu jumping from cell to cell adding gas and taking it away and affecting timing but only if spark changes cell to cell? that is idle qualifty was the issue that post. If open loop i assume "choke enrichment" is not affected as is coolant/spark not affected?

 

As for weather changes, the tuning will change since the tbi ecm doesnt make much use of the MAT sensor in the calibrations. Jsut looks like some adjustments to the BPW as the temperature changes. Youll probably find yourself making small changes when summer, and then winter comes back around. One thing that will help with the idle will be to flatten out the spark and fuel tables at teh area that the engine idles in. This really helps to make for a smooth idle with no fluctuations. Running in open loop at idle may help but if the cam has a close enough LSA to cause problems with the 02 then itll also cause problems with the map readings to the ecm. IIRC some after market ecu's have an option to use the tps to determine the needed fueling with a hot cam so the whoe erratic vacuum issue can be avoided. The stock ecm coudl also be made to do this (uses the tps upon map failure) but id probably just use a cam with less overlap to avoid the issues altogether.

 

Top of post you stated " MAT"? I dont have one but d0e have MAP. in open loop i assume both 02 and MAP are disabled. can you explain the term "flatten out"? I am running what i believe to be conservative tables. in fact i think they are for iron heads and i have alum 64cc? if my idle with current cam 210/216@.05 is desireable and i swap cam could i just leave VE tables as is and disable "closed loop"? i assume at that point i cannot adjust A/F mix as i have no reliable means of measuring it. my 02 AND WB02 will not function? so i could fiddle with the cells it idles in to see if enleanment will help a little but possibly just leave it where it was b4 cam swap? also i can advance spark a couple degrees again in those cells as sparK conservative currently. is that cam 226/234 @ .05 considered to be large(for me) and then wreak havoc on my 7747 SD system? i want to get RPMS to 5800 minimum as i feel my mods will allow more RMS and HP. 5100 rpms now.

 

For those running the '8746 the IAT compensation table for BPC code is in the EPROM. A couple of simple code changes would lower the temperature range of the table. This would allow for better air intake temperature compensation for weather changes when using an open element.

RBob.

edit: this is the table I am referring to: