Man can we just stick one in?Ive benn looking at it for 3 days and am not sure..

 

sticking in an adjustable fuel pressure reg will not change the closed loop AFRs.

The way to get around this is to never let the computer go into closed loop mode. turbotrana disconnected his HEGO and got this to work. you are still going to need a wideband AFR meter to tune it. and the wideband is most of the cost...

 

If you mean just sticking in a wideband HEGO thats not going to work. the wideband HEGO needs a fair bit of electronic control to run it.

 

follow turbo torana's lead on this.

He has the best understanding of how to do this as far as I ma concerned.

Adjustable fuel regulator and wide band HEGO and then build a fuel pressure map to suit the A/F ratio u want.

 

The loop monitor mentioned showed a link but the link went to an ad. for a magazine.
What does it do and how is it connected?
Also curious about the changed input to the computer from the HEGO. The information about the HEGO seems to indicate that it is part of a negative feedback loop which maintains the most efficient combustion of the fuel. Non linear amplifiers are not difficult to make ( maybe a couple of transistors and a diode) but the control of the mixture must be programmed into the computer and that could be non linear.
Two sites just visited
http://www.bobblick.com/techref/projects/o2sensor/o2sensor.html
http://www.mr2.com/TEXT/O2_Sensor.html (self powered oxygen sensor)

 

Thats a pretty cool idea ,maybe getting the resistor values might be tricky though , perhaps that air-fuel kit listed on jaycar could be used to program the right values.

AFAIK the SMT-6 piggyback can modify O2 sensor output , dunno about the others.

 

I've had the wide band a/f ratio sensor (cost $300+) in with the standard ECC4. Basically what happens is when it switches to closed loop while cruising it adjusts it really lean and really rich to the point that you can feel the engine dropping off power as it goes into the lean loop (if this makes sense or answers any questions as I did not read the earlier post in any detail), so its no point using it.

 

The author of one of those links thought that the best way to solve all the problems was to earn more to buy a new car more often.
I will try connecting a digital multimeter to the oxygen sensor. It has an input impedance of 10 meg. Probably just push a pin through the sensor output wire to connect.
There is a problem of the car not wanting to start after standing hot for a certain time. The pump tests good on pressure and resistance and always starts when cold or hot (if the time is not the problem range). Now have fitted a small lamp above the back seat which monitors the voltage to the pump. It was an easy connection using small strips of spring brass pushed into the back of the plug. Also have a monitor for the spark using a 8cm wide strip of al. foil wrapped around the output lead from the coil and connected to a small neon. This gives a very visible glow in the cabin near the hood release. It looks from the circuit that the computer can disable everything.
I need to know the logic behind any changes and this car is a slow learning curve.

 

I am not sure about my understanding of the fuel control system but had the idea that a small adjustment could be possible to the sensor control. This would have to be guided by just how the engine was using fuel under different driving conditions.
This circuit may not be suitable but will illustrate the idea.
The circuit may not be correct but should have a gain of 1 and have an adjustable output volts level pos. or neg. ?

 

I think we are spending too much time on this and it will lead us to a dead end as the ecu's use of closed loop is pretty well limited to light cruise to get past emmision controls when the car ages and is not serviced so its not all that active a lot of the time.

The circuit you need is pretty much like the speedo corrector from jaycar in that its a PWM signal not a discrete voltage.

Interesting but I not sseing this get us anywhere fast.

I played with a pot in series and all I got was a hole in the performance just off idle on light cruise. Couldn't make it do much at all.

 

The idea behind the circuit is not to change the operation of the system but to shift the output from the HEGO into a different fuel mixture range. If the sensor was not working as well as it should then the circuit could be used to correct the output.
The HEGO circuit may be high impedance so the amplifier may need to be close to the sensor. And safer to use a battery supply. 3volt?
A pot would reduce the sensitivity of the system but perhaps a pot. across a small cell to tap off a voltage would shift the output voltage level. As it would interfere with the startup mixture there may need to be some control to switch it on when the system goes into closed loop.
A bit of research would be needed and if my sensor readings are not as they should be then I may try to bring them in range.

 

My HEGO puts out 0.980v at idle... is that uber rich? It blows much black smoke at idle when it's cold.

 

Also, I can only get closed loop action at cruise... never at idle. It wont go closed loop in cruise sometimes too, which I suspect is because it's in limp mode. Any idea how I can tell if it's in limp mode?

 

The problem most of us have is that there is no clear explanation of the computer control available. The output of the HEGO may be ignored by the computer until the engine has reached a certain temperature and then the fuel mix would be changed to shift the HEGO voltage to the required level. It would help if someone could let us know what the sensor should read under different conditions for an engine in good working order.
A rich mixture at idle may be caused by other sensors or adjustments but a list of possible reasons would help. And would the HEGO in good condition indicate the fuel mix at idle? Or when not in closed loop?

 

The HEGO output sensor voltage should vary but it shouldn't be above 0.5v all the time. If it is the engine is rich and the MAP is faulty or there is a vacum leak or you have a cam which has lowered the vacum.

The HEGO output is ignored by the ecu for most driving conditions.

between 0.2 and 0.5v is lean and 0.5 and 1v is rich but the range of the HEGO is very small so off scale is not to be unepected.

 

My HEGO sensor is now officially dead.

When I switch it on it will slowly rise to .990v. Unplugging a vacuum hose to cause a lean will not make it change voltage. Theres no closed loop now. Revving the engine steadily will make it rise to just over 1v... switching the motor off will cause it to drop down to about .7v but quickly go back up to .9v and then slowly drop back down to 0v over about 5 minutes.

 

Your HEGO could well be dead but if you unplug a vac hose and let more air in the MAP will read lower pressure and put more fuel in as it thinks lower pressure engine is under load and or throttle is open wider. This will happen in run mode at idle.

At idle a HEGO will behave as you found normally. 1v rich off scale is not that rich as the HEGO is not a wide band device.

That said the HEGO life is probably less than 100,000km.

 

There may be a way to check the oxy sensor. Perhaps if it was screwed into the lid of a jar and a candle lit inside, the oxygen would be used and the reading could be compared with a good one.
Checked the sensor with a digital multimeter which was too slow to follow the changes but it quickly went into loop and seemed to be reading about .6 or .7 mixed up with fast changes to zero. It seemed to stay in loop when driving or idle.
If the readings were about 1v then the sensor could be good but the signal may not be getting to the computer.

 

http://www.mr2.com/TEXT/O2_Sensor.html

 

http://www.findarticles.com/p/articles/mi_m0BUR/is_4_77/ai_64715531/print

 

It should be in closed loop at idle... I've never seen my EA in closed loop at idle, which I think is either a stuffed ECU or it got damaged by too much fuel from the injectors and low pressure from the fuel pump.

The reason I think the HEGO is stuffed is because I used to watch it behave very differently. It used to go up to .9v quickly after starting the motor.. now it goes up MUCH slower. It used to drop back to almost 0v when switching the motor off, now it SLOWLY goes back down over 5 minutes... I'm talking about this thing having a voltage differential UNPLUGGED... the thing seemed to generate it's own voltage. I thought my multimeter was stuffed. I'm guessing they contain some sort of semiconductor that has broken down due to heat and there are 2 different metals now contacting eachother generating the voltage (???)

Anyway I'm not keen to fit a new one until I'm certain the rest of the system is working and wont destroy the new one.

 

I've never had closed loop idle either until the EGO was replaced . Mind you it didnt fix all the idiotic behavior of the ECM but it did help ,better economy too.