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Topic Review (Newest First)
05-29-2012 04:25 PM
B-1 Thanks to all of you guys!
05-29-2012 04:22 PM
B-1
Quote:
Originally Posted by T-bucket23
Leave it, drill a hole in a more convenient spot and weld a bung in and you are done.
Straight forward advice T-bucket23. Will probably braze the broken one at the top, saving threats to my exh. manifold and install another somewhere before the cat. I've seen enough stuck fasteners to know it ain't gonna be pretty after messing much more with the old one. On an engine stand - could be done while eating a sameech; either removing OR damage recovery.
Thanks!
05-29-2012 04:13 PM
B-1
Thread Fiasco

Messing the pants is so easily achieved these days with everyone's sensitivities on the surface. As concerned as I am about it would mean chopping the car down to a trike and setting in a chair to replace the 02 sensor, which is probably what will eventually happen if the ride has a major "lay down". But it's going strong/good enough. I'll fix it, yeah.
But did you ever just wonder? Well you can't in some circles apparently.

Anyway, the magic crossover number around .450 MV then if 02 sensor not responsive enough reads the tables in the ECM. Like all of the other less critical senors (excluding CPS exploding & such). Typical fare.

I'll keep me wonderin' to myself around here and keep it on book level learnin'. Take it easy on your nerves cobalt327, It's only questions in life. Nobody asked for the vault key.
05-29-2012 04:06 PM
T-bucket23 Leave it, drill a hole in a more convenient spot and weld a bung in and you are done.
05-29-2012 03:23 PM
F-BIRD'88 On that EFI system the O2 sensor acts only like a on off switch
Its either in teh low state or the high state.

less than .450MV or more than 450MV. The ECM dos not care otherwise and you cannot trim or bias the O2 sensor voltage up or down.

the computer still looks for the .450MV cossover. If it don;t see it or the sensor response is slow. The ECM just ignores the O2 sensor and reads the tables
AND THROWS A diagnostic code.
Now it will not run in closed loop mode at all.

You cannot tweek the O2

running extended time in limp mode will make the O2 sensor get dirty with carbon and fail.

The whole purpose of the O2 sensor is to allow the ECM (while in Closed loop mode) to maintain a idle and cruise 14.7:1 AFR so the cat converter functions correctly.

The cat converter will soon fail too with extended limp mode driving with a fubared-disabled O2 sensor.

If any of the sensors are reading out of spec to the ECM it will not run in Closed Loop at all.

You sure can sure piss everyone off.
05-29-2012 03:08 PM
cobalt327
Quote:
Originally Posted by B-1
I expected to hear more "what if's", but I guess most don't want to break ranks from the norm. It's that sheep thing that civilization is built upon I guess.
I don't know what you're smoking- but this is an example of some "thing", all right. Like if you hadn't crapped the bed removing the sensor in the first place, this wouldn't even be an issue. And it has not a damn thing to do w/sheeple, my friend. But it has a LOT to do w/practicality and results obtained from effort, time and money expended.

No one here is going to spoon feed you directions to try to fake out the O2 sensor when you have been given the obvious, cheap, easy solution already: simply replace the sensor and be done w/it.
05-29-2012 01:37 PM
B-1
Quote:
Originally Posted by sbchevfreak
Here is how it works, without getting into too much detail:

The 02 sensor is just that, it senses how much residual oxygen in in the exhaust stream. There is a material in the sensor tip, that generates a voltage between 0v and 1v, roughly, when exposed to oxygen. The sensor has to be at or above 660* F to work, which is why the old 1 wire sensors were mounted in the manifold, so that the exhaust would heat them quickly. At .450-.500 volts, this is the "ideal" mix. Above and below, rich/lean. This cycles in the milisecond range. A fixed voltage will not work, and you cannot manually switch it fast enough.

fbird's idea with the 4 wire sensor mounted furthur down the pipe is a good one. The sensor will be every bit as accurate, likely even more so, as the original. The heated sensors were brought into use because the 1 wires had a tendancy to cool off below threshold, and drop the fuel system into open loop, increasing emissions. The solution was to add a heater circut that was ECM controlled to maintain sensor themp above threshold. In reality, all the early ECM did was turn on the 12v feed to the heater when the car was stared, and turn it off when the car was shut off, so a switched power realay feeding 12v to the heater circut does exactly the same thing.

Your methods will not work. It is time to be rational, and realize that by the time you "engineer" a complicated jimmy fix to fool the ECM, you will have spent more time and money than the car is worth. If you do not want to put in a heated sensor down stream of the original one, you need to remove the original sensor, and replace it. There is no in between.


Going on the limited understanding I had of the 02's physical and interactive characteristics and knowing that the voltage cycled through a very limited range, that was the direction I was facing. Now when you say millisecond cycling, I can understand that. I have not given up on replacing the original sensor or installing another further down stream. Over two days work has been focused on removing the old one. I don't give up easy. I'm throwing ideas around for feedback. All I'm hearing is it's impossible to fool the ECM, but a MAP enhancer does just that, right? Nothing is impossible. But as I continue until the repair is completed, I can't take a purist outlook & say it can't be done. I expected to hear more "what if's", but I guess most don't want to break ranks from the norm. It's that sheep thing that civilization is built upon I guess. Well, I'm not going to butt my head up against that wall. I'll let you know if and when it can be done. Computers and programs can control & deceive other computers. Cost is no factor to achieving something worthwhile or to prove something can be done differently. But Time, Ah, time is a different matter. Priorities come into play. But I stick by the fact that many things CAN be done. I'm glad you posted sbchevfreak. I had your post in a tab from http://www.hotrodders.com/forum/temp...-191490-2.html. Saved me from looking in the manual for those specs. Good day friend.
05-29-2012 01:03 PM
sbchevfreak Here is how it works, without getting into too much detail:

The 02 sensor is just that, it senses how much residual oxygen in in the exhaust stream. There is a material in the sensor tip, that generates a voltage between 0v and 1v, roughly, when exposed to oxygen. The sensor has to be at or above 660* F to work, which is why the old 1 wire sensors were mounted in the manifold, so that the exhaust would heat them quickly. At .450-.500 volts, this is the "ideal" mix. Above and below, rich/lean. This cycles in the milisecond range. A fixed voltage will not work, and you cannot manually switch it fast enough.

fbird's idea with the 4 wire sensor mounted furthur down the pipe is a good one. The sensor will be every bit as accurate, likely even more so, as the original. The heated sensors were brought into use because the 1 wires had a tendancy to cool off below threshold, and drop the fuel system into open loop, increasing emissions. The solution was to add a heater circut that was ECM controlled to maintain sensor themp above threshold. In reality, all the early ECM did was turn on the 12v feed to the heater when the car was stared, and turn it off when the car was shut off, so a switched power realay feeding 12v to the heater circut does exactly the same thing.

Your methods will not work. It is time to be rational, and realize that by the time you "engineer" a complicated jimmy fix to fool the ECM, you will have spent more time and money than the car is worth. If you do not want to put in a heated sensor down stream of the original one, you need to remove the original sensor, and replace it. There is no in between.
05-29-2012 12:20 PM
B-1
OxySensor Fiasco

By the way, this engine runs smooth much of the time; idles easy without the 02 connected, except sometimes pulling a heavy load it will run a little rough because of the rich fuel mixture I guess. Pull in to get gas and restart to a smooth idle, zippy take-off. Haven't had any plug trouble. All of this has led me to believe that this OBD1 system is not as finnicky as I originally thought. That's where the "fooling the ECM" idea came in. I thought I might join the idea of manually leaning out the fuel mixture and injecting HHO. Mind games.
05-29-2012 11:55 AM
B-1 Back to work my friends.
05-29-2012 11:54 AM
B-1
Quote:
Originally Posted by cobalt327
The O2 will change the a/f ratio VERY rapidly, it's far from stationary except at WOT. You'd be better off leaving the sensor disconnected than to feed the ECM false info. That's just not gonna work. If you can braze, just fit a new bung, seal off the old sensor and be done w/it. But w/o an O2 sensor working, ain't no way you're gonna pass inspection.

Here in WV, as long as the brakes, tires, lights, glass, exhaust are in tact with no body parts flapping in the wind; it will pass.
Hard to start and rough running engine raises no eyebrows. THANK GOD!
05-29-2012 11:44 AM
cobalt327 The O2 will change the a/f ratio VERY rapidly, it's far from stationary except at WOT. You'd be better off leaving the sensor disconnected than to feed the ECM false info. That's just not gonna work. If you can braze, just fit a new bung, seal off the old sensor and be done w/it. But w/o an O2 sensor working, ain't no way you're gonna pass inspection.
05-29-2012 11:37 AM
B-1 Oh, cobalt327, thanks for the analysis on tricking the ECM with a "middle of the road" voltage. Now THAT gives me something to chew on. Thanks!
05-29-2012 11:34 AM
B-1 When I get this PC job out the door and the rain passes over, I am going to get the beefier torch tip and give it another go, but I'm going to get some brazing rod too so I can legally drive it AND occasionally work on it till I get it in decent order. If time runs out on me before inspection, I'll slap the "Farm Use" magnetic signs on the door until I get a proper repair. hehe
05-29-2012 11:25 AM
B-1
Quote:
Originally Posted by cobalt327
The problem w/"tricking" the ECM by feeding it a middle-of-the-road signal is the air/fuel ratio will be correct only a tiny portion of the time. I'm sure you could get the engine to run, and possibly run well enough that you don't kill it immediately- but the only sensible thing to do is remove the old one or weld a new bung and install a fresh sensor there.

Thanks for the reply cobalt327. Yes, that is the sensible and desirable thing to do. This car is a work car. I mean very often pulling a half ton load. It works so well at doing it that my F-250 is still setting in the garage stripped down to a short block waiting to be fixed. As a journal note - The car is a clunker in most peoples eyes. I looks fairly good, but it has held up to very much and will be used as long as it doesn't take up too much time to maintain. If all else fails, cobalt327, I'll do the job right, when I get the time. Too busy to get too overly involved right now, but always time to consider things and experiment. I mean, it's a 1988 Regal and there are other things to be repaired, like the house, guitar, truck, bike, customer PC's. hence the need to get this car to pass inspection and repair better when time permits. I know if I end up pulling the head to repair broken manifold bolts and stuck 02 sensor, that will tempt me to do a total rebuild. Probably nobody but me can relate to that. Thanks a bunch for your sane and proper answer!
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