86z28iroc-z

Not sure if this is normal for OPEN LOOP, but i just noticed lately that if I start my car from a cold start, and let it warm up for a good minute and took off, it felt like it had no power, and then another 2 minutes down the road all of a sudden bam! it had power again. So I hooked it up to my computer and stated datalogging, and i noticed right away that during the OPEN loop stage, my SA will sit at 28 and slowly drop every 40 seconds or so and keep dropping, it'll go down to 20* and my TARGET AFR will be set at 15.3 and it'll spike and drop for an instant here and there to 30 and 0... But as soon as the OPEN loop timer (250seconds) kicks in, my SA will jump back to the table, and my TARGET AFR will go to the 14.7 which its supposed to be at. What's the deal here? That can't be normal can it? I've got a 4-wire o2 so it'll start making crosses before the 250seconds are up, so i'm wondering if I should lower the timer or completly eliminate it, but I'd like to know why open loop is doing this?

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'86 Iroc-Z -_-_- 357 TPI -_-_- Rebuilt 700R4 w/ heavy duty TC -- shift kit -- -_-_- Lunati Voodoo 60101LK -_-_- Dart Iron Eagle SS heads -_-_- CC Pro Magnum RR -_-_- Heddman Hedders & Y-pipe -_-_- Flowmaster 80 -_-_- Ram Air -_-_- Astrostart -_-_- Daily Driven

hmx

I'm not 100% sure because of your description, though my car has a similar problem. It appears that operating in open loop mode, it has some power sag, but runs fine around town in closed loop mode. The problem is exacerbated in colder weather, as it takes longer for the car to get into closed loop mode.

I'm seeing high BLMs, too, which means that my car is 'seeing' a lean condition and is trying to correct for it (which has to do with my fuel injectors, I'm pretty sure... see my thread in this board). Because the Open Loop mode doesn't correct for this, the car has too little fuel and sags out when in OL mode. When in CL mode, the BLM can correct for my fuel injectors and thus there are no problems.

What are the rest of your readings on your datalog when the car is hot? Are they normal or out of whack?

86z28iroc-z

Everything is normal/perfect in closed loop. My BLMS are 124 when really cold and 129 when not as cold in open loop and it stays around 128 in closed loop +-1or2 the only thing that's weird is my SA and my Target AFR in open loop.

My fueling is ok in open loop, i'm sure it'd be alot better if my SA and Target AFR wouldn't be wacked out.

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'86 Iroc-Z -_-_- 357 TPI -_-_- Rebuilt 700R4 w/ heavy duty TC -- shift kit -- -_-_- Lunati Voodoo 60101LK -_-_- Dart Iron Eagle SS heads -_-_- CC Pro Magnum RR -_-_- Heddman Hedders & Y-pipe -_-_- Flowmaster 80 -_-_- Ram Air -_-_- Astrostart -_-_- Daily Driven

86z28iroc-z

I did some poking around and found that it is dependant on the set time of closed loop timer, and the SA is 20* plus whatever is in the Spark Correction - LV8 vs coolant temp table. and it'll sit at that value no matter what until the timer has run out.

The Target AFR is dependent on the Afterstart fuel enrichment table.

So I changed the timers to 15 seconds and 30 seconds for the hot and warm and left the cold at about 160 seconds; changed the SA Correction table to 8.5 degrees in the bottom and 0 up top, so it'll stay at 28* during warmup, and then made small changes in the Afterstart table to make the Target AFR be 13.1:1 and slowly trickle up to 14.7 by the time the timer runs out.

So far, so good. Will keep datalogging and testing, but the engine seems happy with it.