Hey guys, i have a problem. I want my ECU to stay in open loop at idle. It isn't cooperating. I think its in my settings. Tuner Pro ECU - 7747 - ASDU based open loop MPH thresh = 5 open loop idle thresh tps% = 2.73 open loop idle off = 0 open loop idle on = 900 I may try reversing open loop idle on = 0 and open loop idle off = 900. I read alot of threads but i couldn't find an answer. Can someone please help? ---------- Also my "Idle 02 error correction" was set to 0. Stock was .75. i may set it back and see if it helps.

Quite possibly Watson, that there is no way to run a 7747 in open loop idle. Very inquisitive my dear Holmes. Watson, take notes. Perhaps maybe if the Fuel Map is richer than open loop idle, the ECM uses the richer value ? Eh Watson? Why certainly Holmes.

Is it possible Watson, that i have asked a question that no one can answer? I'm not sure Holmes. Perhaps my dear Watson, that I'm going to have to use my ingenuity here and figure this mystery out FOR them?

IVE GOT IT my dear Watson! We will present the problem to Professor Mauriartti, the only advocacy capable of defeating me. Ah yes Holmes, good call.

Just an idea here guys, but..... what if i tweaked the main fuel map @ idle out of the R/L thresholds forcing the ECU to go into O/L. Come on guys, i know at least one of you has worked with this before.

Michal, here are settings that should work for an open loop idle. However, I don't know if you have a binary definition file for these parameters. The values shown are raw BIN values. The comments have the actual values:
A bunch of the BBC trucks ran open loop idle. Checking those BINs can help.

RBob.

ALOT of small block vans did as well. The 02 sensor is located in the Y-pipe on 1/2 ton models until like 1991 and does not stay hot enough if the engine is allowed to idle for any length of time.

I switched to a heated oxygen sensor and recalibrated mine to an ASDU truck based calibration in order to stay in closed loop.

HEY! Thanks guys, i will apply those settings and go from there.

Fricken closed loop idle . I think my camshaft is messin with the idle. I dunno what happened, i spent along time trying to get the thing to stay in closed loop stock, and it never would. This is makin me CRAZY. I dunno, call me crazy but.... i think these might do something with the idle.


02 AFR Bias value - 43.60mv
02 Prop term duration @ idle - 16.00
02 Prop gain factor at idle - 16.00
INT delay bias at idle - 0
Error factor for rich 02 - 0.91
Idle 02 error correction - 0.75


The problem im having is in closed loop @ idle the ECU is subtracting fuel untill the thing dies at a stop sign. I may have to go back to a stock bin and go again. I tried adjusting everything and i dont know how i screwed it up lol. Not sure what Prop term, or prop gain is, but if i can get the thing to quit correcting at idle would be great lol
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I seriously think its the overlap of the camshaft, sisnce the rpm band of it is 4000-7200. Im sure with the right settings it will work.

I have noticed my car does still does go C/L in gear most of the time. Goes into O/L in park more. I changed my 02 sensor from the small tip bosch back to the original AC delco unit and ive noticed it takes a bit more to go into C/L. Now, the Bosch 02 sensor would hold a voltage after the engine was turned off (i dont think its supposed to do that) like 850mv or 982mv and would take considerable amount of time to reach 0mv. I was thinking about my RICH 02 THRES setting of 850mv, if i were to up the fuel map at idle to go over that, and turn the delay to O/L to 0 seconds,that may force it to idle in O/l, and solve my idle issue. I also have the 083 ECU that came in the car. Im going to fiddle with the O/L and C/L AFR'a a bit. I just cant remember what i changed. This car used to idle O/L all the time. Actually, im going to up my "02 AFR Bias value" from 43.60mv to 366.00mv. One would think adding bias voltage to the 02 voltage at idle would trick the ECU into thinking its richer than it really is. I will see.

You know, i leaned out o/l by 2 points ( i think cause of the lack of vacuum) and the frickin thing kicks but in O/L. Is there a manual or some site that will explain the terminology? I prolly wouldnt ask so many questions

The O2 sensor going offline (open loop) at idle is frequently due to too cool of an exhaust mixture on the OEM one wire sensors. Is that what you're using? A one wire O2 sensor? Do you have headers? If so, you should seriously consider converting over to a 3 wire heated O2 sensor like the AC Delco AFS74 sensor used in the early to mid nineties trucks and cars. Stay away from the Bosch sensors if you can, a lot of the more knowledgeable folks on this forum swear they are no where near as accurate as the GM/AC Delco sensors. Just my two cents for ya.... YMMV

Hey vernw,
I just read your post and I am having the Open Loop problem at idle with a Bosch O2 ,my question is on the heated ac delco sensor is this a direct hook up from the one wire sensor or will you need some mods to make it work?

Ok guys, i just figured out how dumb i am. A while back i painted my timing mark on my balancer, well, my car seems to start the stronger @ 23 degrees initial, so i painted another line on the balancer 20 degrees off so that i could set it at 3 degrees which would really be 23 degrees, but i put it on the wrong side .I now have it set correctly and the thing idles like normal. Also i set my settings to that BB bin too. My engine seems to "windmill" below 19 degrees unless something else is off. Id rather the thing spark knock when the first piston fires. i dunno. I think ill search around the threads to find the best way to set initial.

Prop Term duration 02 Error all set to 0.20 and Prop Gain is all set to 3. Now instead of gradually adjusting idle, now the thing oscillates at idle, if i change Prop Gain to 0, will that make it not adjust the idle?