82 Prom Operation Question

You don't synch the IACs, they are wired parallel and don't need synching as of that, the pos is the same for both.
I think (have not tested this) that the IACs only follow the throttle above 75%, they open all the way then. For the rest they settle at the base position (which is in the prom somewhere as a setting for throttle down pickup so the engine doesn't die)

The BLM has a large range but only a small effect on injector opening time. The INT is what's most important here. Removing the cat really doesn't have that much of an effect, the biggest chokes are still the heads and cam and as a result the engine will run fine. We have a souped up 82 here with a bunch of mods and it's pushing way past 300 horse, runnning the stock ECM but with a tweaked up fuel pressure. Still fiddling with that eery now and then though.
 
Twin_Turbo said:
You don't synch the IACs, they are wired parallel and don't need synching as of that, the pos is the same for both.
I think (have not tested this) that the IACs only follow the throttle above 75%, they open all the way then. For the rest they settle at the base position (which is in the prom somewhere as a setting for throttle down pickup so the engine doesn't die)

The BLM has a large range but only a small effect on injector opening time. The INT is what's most important here. Removing the cat really doesn't have that much of an effect, the biggest chokes are still the heads and cam and as a result the engine will run fine. We have a souped up 82 here with a bunch of mods and it's pushing way past 300 horse, runnning the stock ECM but with a tweaked up fuel pressure. Still fiddling with that eery now and then though.
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Yes, I already knew they were wired in parallel, and I hear you on the base initial position that starts decel control to idle when the throttle is lifted. (vs throttle following like is done on my Accel Gen VII) I don't know for sure, but I bet the IAC's are position synchronized when the ignition key is initially turned on. There has to be some initialization sequence that insures the stepper motors are positioned where the ECU thinks they are. Anyway, still don't understand what you meant by "reset" at 35mph / closed loop. What's going on there?

Bullshark
 
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I'm not sure either, if someone has an 82 shop manual maybe they can look it up. I think it was in there. On startup the steppers most likely go to a pos as indicated in the prom.
The "reset" is exactly what it means, above a certain speed (I think it was 35mph) the IAC motors go to pos 0 (or 1 from 256 positions) and then go back to the desired position for the current engine variables. This only happens once after starting the engine, it won't happen again unless you turn the ignition off.

Another thing is, when you turn the ignition off the IACs probably "park" in a certain position (maybe someone can check that, I never bothered to) and therefore it may be wise to turn the key off and leave it off for some time (10 secs or so) before unplugging the IAC, so that it's "parked" in the correct position. A lot of injection systems do this so I assume the GM stuff does too.
 
Twin_Turbo said:
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The "reset" is exactly what it means, above a certain speed (I think it was 35mph) the IAC motors go to pos 0 (or 1 from 256 positions) and then go back to the desired position for the current engine variables. This only happens once after starting the engine, it won't happen again unless you turn the ignition off.
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Ah, that's what I initially thought you meant. And , That is the sequence I was calling sync. I just find that a little strange. What happens if it is busy reseting when you need a decel control after a rapid throttle lift. I guess the IAC response is quick enough to handle that situation??. Just thinking out loud here. :bonkers:

Twin_Turbo said:
Another thing is, when you turn the ignition off the IACs probably "park" in a certain position (maybe someone can check that, I never bothered to) and therefore it may be wise to turn the key off and leave it off for some time (10 secs or so) before unplugging the IAC, so that it's "parked" in the correct position. A lot of injection systems do this so I assume the GM stuff does too.
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Yes, I think you are correct about that. Takes alot less than 10 sec I bet. :drink:

Bullshark
 
The 82 Service Manual says that the IAC motors will reset after reaching a speed of 45 MPH or greater. Somehow on cold start the IAC motors open up to act as a choke until a certain temp is reached. Hopefully mine will do this after replacing the O2 sensor to the collector area. I have already purchased the heated O2 sensor fwith 3 wires for the cold start improvement.

Thanks for the Help!

Herb
 
I got the heated O2 sensor installed today. I had to put it in the spot where I already had the bung. Anyway after wiring it up I got some good data. The IAC motors did start to work. By watching the flad data on WINALDL all of the IAC boxes had check marks. I think the idle setting was 22 on the IAC position. Sounds close to what Marck said. After watching the data being collected, I started to learn how to interpret the data a little better. The ECM goes into closed loop pretty fast. I am now starting to hear the engine hunt. By looking at the data, it appears that the O2 sensor is going high then low. The flag data goes from normal to rich. I think that this agrees with the ECM trying to balance out the system. The car is running very rich. I hope that moving the O2 into the collector area will solve this problem.

I powered the O2 with power from CKT 39 ( Pink/Black ). I don't really know what the current draw should be for the O2, and I don't want to overload this CKT. I know it needs to be on a switched CKT.

Does any of this make sense?

Thanks

Herb
 
I checked, IAC position normally should be around 20 so you're good there.

The O2 sensor only properly detects lean conditions, so the system always leans out the mixture until the O2 pics up a lean mixture and then the system goes into enrichment mode and automaticall leans out when the lean cond. is gone. It cycles like that.

Remove the 12V from the ECM for 30 secs to wipe the BLM, with your old O2 sensor it will have screwed up all the fields and starting off fresh will populate them faster with correct correction numbers.

I would advise you strongly to use a fused relay to power the O2 sensor, do not pull power from any of the ECM wires. Use the oil pressure sender 12V to fuel pump wire to switch the relay, that way it's always on when you have oil pressure (and not needlessly on when you just have the ignition on)
 
Marck,

I checked the voltage on the oil pressure sender wires. The orange wire had 12V, & the brown wire had like 8.6V. I don't know why this was like this, so I picked up CKT 39. I am assuming you mean one of the brown wires, not the orange.
 
You need the tan/white wire. The tan one is for the gauge, the orange is the 12V source.
 
While checking the wires to the oil pressure switch, I noticed that the engine will run with the connector disconnected. This doesn't seem right. It seems that I still have wiring problems somewhere! Orange wire is hot at all times, 1 drown wire switched, 1 brown wire with nothing. This is part of the engine harness I think, that was just replaced with a new one.
 
Look carefully, the wires are actually tan (discolored to brown) but one of them has a white stripe on it. That's the one you need.
This is not part of the engine harness, it's part of the harness that goes to the HEI and TCC.

Orange should be 12V continuous (not ign. switched) it's the feed for both the pressure switch and the relay. It's fused directly off the main battery feed.
 
Things are getting better with the O2 change. I will get the O2 moved in the morning. I am still not getting a high idle when cold. I checked the sensor, wiring at the firewall, and back probed the pins on the ECM. The resistance stayed at 3400 ohms cold. At around 160 it was at 500 ohms. I still wonder if the prom could be having some type of problem not seating properly? The only other thing that I have not changed is the TPS. Going from normal to WOT, I am getting some funny resistance readings at around 3400 ohms. At the voltage side, everything looks ok. It might just be the digital VOM. Can the TPS affect the cold start.
 
I think I have found the problems. The 4 wires on the IAC connector were melted pretty bad. When I made up the new harness, 2 of the wires were backwards. I found an 82 at a local shop this morning, and was able to verify the wires. Blue/black & Green/Black were opposite corners. It make sense after thinking about it. 1 ckt runs it in, & 1 runs it out.

One other thing I found today was the cannistor vapor solenoid wires were also backwards. These came out of the plug when removing the harness. I never thought that the solenoid was that important, and that it was only a sensory device. Once it was reveresed the O2 voltage stablized, and the engine stopped searching. Someone can tell me how this plays such an important role. I am guessing that it controls the vacuum in someway. Other than running a little rich still, I think everything is back to normal. Tommorow when I get a cold start high idle, I will know for sure.


Thanks for all of the help.
 
The canister purge solenoid, when opened lets fuel into the engine from the vapor canister. It comes in with the air from the PCV, additional air + fuel -> high idle.
 
Twin_Turbo said:
The canister purge solenoid, when opened lets fuel into the engine from the vapor canister. It comes in with the air from the PCV, additional air + fuel -> high idle.
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I actually had a low idle, that affected the O2 causing the voltage to go from .2 to .9v. With the connector unplugged, it had the same effect when I reversed the wires. The wires were pink & green.

When the ECM learns the ( BLM ) I think, will it lean out some? Should the cannister purge valve checkmark stay checked on WINALDL flag data. My AC check mark also stays checked when off? I don't understand all of the data, but I'm started to think about what it's telling me. That's scary!:lol:
 
Marck,

I am still getting a low idle on cold start. It is around 600 RPM. I have been reviewing past ALDL data, and have noticed that the O2 readings are staying around .85v. The past good data I had before the headers was around .45v. You commented earlier that it should be around .4v. What does this mean, & where should I look now. Should I try the old O2 sensor to see what happens? Could the new 3 wire O2 have a different claibration factor? I will try and copy the old & new data to an Excell doc, and try and post that way.

Thanks

Herb
 
Just read your other post. If you can post the data concerning BLM, INT, knock & cross counts and such here so we can have a look at it. WinALDL should be capable of exporting a log. I'll have Jonas chime in here, he wrote the program.
 
Twin_Turbo said:
Just read your other post. If you can post the data concerning BLM, INT, knock & cross counts and such here so we can have a look at it. WinALDL should be capable of exporting a log. I'll have Jonas chime in here, he wrote the program.
Click to expand...

It saves a log, but they are to big to import. I will see if I can put the data into Excell and paste back in columns.

Thanks
 
Dirtbuster1 said:
I think I have found the problems. The 4 wires on the IAC connector were melted pretty bad. When I made up the new harness, 2 of the wires were backwards. I found an 82 at a local shop this morning, and was able to verify the wires. Blue/black & Green/Black were opposite corners. It make sense after thinking about it. 1 ckt runs it in, & 1 runs it out.
Click to expand...

Dirt, you have my head spinning. Your chasing more tails than a stud in a field full of mares. So all this time the IAC(s) were out of control?? No telling what effects that had, depending on the IAC position it was driven to. If it went wide open then it would cause a lean condition, assuming the engine reached operating temp and went into closed loop, the O2 sensor would probably peg to the rich side trying to compensate. Not to mention the fact that, the BLM parameters would also bias trying to correct. Have you corrected this and verified proper IACs position / control? Why don't you try checking each sub-system out individually. When trying to troubleshoot these systems you need to eliminate all the variables and focus on one thing at a time. Is there anyway to disable closed loop operation and disconnect the fuel vapor canister etc.etc.. Those things are just confusors right now. You should be able to get this thing running pretty smooth with just a basic setup and then add these functions back in the control loop systematically one at a time. Trying to chase the cause and effect of all the subsystem elements simultaneously has you chasing your tail.

Maybe it's time for a tech day down in Georgia . You ready to make the trip back TT. :D There has to be an expert down there somewhere that can give you some trustworthy hands on help. Two heads/eyes are always better that one.

Bullshark
 
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I just got off the phone with Bosch. Basically he is saying the same thing as Marck said. He suspects that the 1 wire sensor must go above .5 v to go into closed loop. I saw this last night when I idled the engine up in park. It will only stay in closed loop for a short time. With the heat O2 he agrees that it will jump into closed loop based on the heater. However he said at .9v, that it is running to rich. He said to create a lean condition by unhooking the brake booster to see if the O2 would drop in voltage. If the voltage will not drop, the sensor is most likely defective. At least this gives me some direction for verification of the sensor. If the voltage on the sensor drops, what do I do to lean out the mixture? Or what can I do to cause the 1 wire back into closed loop. It seems that we are narrowing down the problem, but it sure is not easy.

Thanks,

Herb
 
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