Scott 89t2

even at idle .03 seems to low. that's basicly 0. I'd be thinking shorted 02 harness wire. unplug the harness at the sensor. and re check the voltage and see if it goes up. if it's still that low the sensor might be shot (possible from the short so re do above test after you change it). I think it should be atleast 0.1 at idle.

Rob500

So it is A and E. Good I'll try that. I am going to look at the solinoid also.

eljefe62

I thought if anything was wrong with o2 sensor, the 'check engine' light would be on?

Rob500

That is what I thought originally. That the O2 sensor was bad and the computer was trying to richen the mixture. But I should get ecu errors if the voltage is low and I don't. That is way all the questions about the feedback loop. By the way the voltage is that low. Tested by pulling the harness plug off and checking the output directly at the sensor.

eljefe62

And also, heard that a better sensor (like for wide band monitoring) could be had from an early 90's civic (the UEGO sensor?)
what's the differences in sensors?

HAILERS

eljefe62
The sensor you mention is not compatible with the ECU in the RX-7.
That sensor is used in a WideBand kit to accurately measure AFR across the full throttle range. The stock is only accurate for Stoic, around .4mv. It loses any accuracy below and above that range.

http://www.techedge.com.au/vehicle/wbo2/wbo2.htm

HAILERS

Well, I just warmed up my 87N/A. I have a wire tap into the 02 sensor. It read 0.1volt. I pulled the Blue connector off the Relief solenoid. The meter now read .8volts. Thats because all the airpump air is now dumping overboard(Blue plug disconnected).

I disconnected the 02 sensor. No codes. Hmmmm. I think this is because the car is not being driven. I know my code checker is working because I pulled off the plug to the air intake temp sensor and it put out a code for that.

When you get home, look at the 02 sensor voltage at hot idle. Then pull the Blue connector off and watch it go to ???? .8 or so.

Change your o2 sensor prior to your next emission checkup. Bosch is only 20-25 bucks. Never hurt to change it.

Rob500

I think that is a good plan. This is a very informative thread and I really appreciate the help / ideas.

Rob

Scott 89t2

ya just change it... my wire got shorted last year and was reading almost nothing with it pluged in or not. I changed the sensor and got a normal reading with it unpluged but still 0 with it pluged in. so the wire was shorted. causing the first one to die. so I had to run a new wire.

on my S5 with the o2 unpluged or when shorted. it took about 20-30 mins of driving for the engine light to come on. but the code did store right away. if you have an S4. I woudln't even bother checking for codes that system never works anyways.

Oversteer

This a great thread...Per Hailer's note from above, I pulled the lower hose off the ACV and it was dumping air...at idle, and about every other engine speed. My car wouldn't pass emissions either.

What is the issue with the ACV "dumping"? Any known causes?

Thanks..

HAILERS

Remember, the engine needs to be warm(hot)when doing this. At cold engine temps it may dump until the water temp gets up.

Also, on a 86-88 make sure that the water temperature switch on the Bottom of the radiator has both connectors on it.

So if the engine is warm/hot, pull each of the two vacuum hose that are located just above the ACV, off. Feel to see if each has a vacuum on them. If both have a vacuum on them, then there might be a problem with the ACV internally(not likely on a N/A).

Most likely what you will find, is that one of the vacuum hose has NO vacuum on it. So write back as to what happen as far as the vacuum goes. I have to stop right here because I forgot which hose goes to the Relief solenoid and which to the Switching solenoid. I'll have to go look at my n/a which if far, far from where I am right now. Maybe tomorrow.

Well maybe one more word. It's(dumping of air) usually related to the Relief solenoid (Blue connector) not getting either a ground signal(ECU0 or no 12v on the black/white wire when the key is to on. The lack of a ground can be related to the setting of the TPS or a blown transistor in the ECU. So you'd want to pull the blue connector on and off while feeling the solenoid it is connected to. And feel the solenoid to see if it clicks as the blue connector is pulled on and off. It should if the engine is fully warm/hot.

Oversteer

There is vacuum in both lines, and with the key on, if I disconnect the blue connector, I can hear it clicking so I know it's getting power and ground. There may be other issues. I checked the voltage off my new Bosch O2 sensor and it read 0? Blue solenoid disconnected, 0 volts? I traced the O2 wire back to the ECU to make sure the harness was good. What gives?

Also, when you are referring to the A and E pins, are those on the plug sitting on the front of the pass side wheel well? My car is an S4 TII Convertible....if that makes a difference.

HAILERS

Oversteer.....on your series four, you have suction on both vac hoses just above the acv? And when they are put back on the metal nipples you still have air dumping out the relief port on the bottom of the acv??? Is it dumping air big time or just a whisp?

Try this, feel the air being dumped. Now pull the blue connector off the relief solenoid on the left side of the engine. Did the air being dumped increase a heck of a lot???? Or stay the same. Should increase dramatically.

By the way, those two hose above the acv can get crossed. Try this: pull both vac hose off. Make sure they both are sucking. Now pull the blue connector off the solenoid. One of the hose should now stop pulling a vacuum. Did that happen???????

And about the tps. No. Forget about A and E. That was for Rob500's series five tps. You do not have that type of tps. Yours is just a three socket connector(not that green thing) on the end of the tps harness. Fully warmed(hot) engine, you can take a digital meter and put the meter on dcvolts, negative lead on a good ground, and the positive lead into the back of the tps connectors GREEN/RED wire. You should see 1 volt if the engine is hot/warmed up. If not just turn the tps screw til you get one volt.

After you check the above items, and you don't have a thing to do, turn the engine off. Now pull both of those two vac hose above the acv off. Now get a piece of vacuuum hose from somewhere, and put it on one of the open metal nipples. Now suck on the hose. You should be able to maintain a vacuum on that hose. If not, the acv diaphram is busted or you have a real bad acv gasket(leaking). Do the same with the other nipple. Suck and make sure you can maintain a vacuum. If not, the diaphram is busted in the acv or you have a leaking acv gasket.

HAILERS

Oversteer
About the 02 sensor. Hmmm. It sounds like maybe you have accidently grounded the 02 sensors center conductor to the shielded wire. I'd disconnect the 02 from the cars harness and put a meters positive lead on the 02 sensors wire then the negative lead on a good ground. Put the meter on dcvolts and start the car. The meter should read something b/t 0.1volts to about 0.8 volts. What happened?

If you did accidently ground the 02 sensor, don't worry. I don't think you can hurt it by doing that.

Oversteer

OK.... I ran through this again just to double check. Set the TPS to 1.0V. You were correct avoid the O2 shielding wire touching the center wire....fixed that one. The reading at idle with all emissions intact is .65V...That's approxiametly what I was expecting with the blue connector unplugged. The blue solenoid is working fine. I checked the vacuum lines on the ACV. The 2" line going to the top of the ACV has vacuum, neither of the others do. At idle, the car is still dumping. It continues to dump throughout the rev range. Since the car's temp comes into play, could a faulty temp sensor be sending the wrong signal to the ECU (essentially telling the ECU that the car is cold)? If that were the case, that might explain why the O2 voltage is as high as it is with everything connected....

Whew....this car is complex! Thanks again for all your help

HAILERS

Oversteer.......So the way I understand this, is that the Blue solenoid clicks when the engine is warm/hot. But NEITHER of the the two small vacuum lines located directly above the acv have a vacuum on them? That's what I just read.

I'm being thrown off by the mention of the 2" line. I'm assuming that that is the hose b/t the acv and the airpump.

If the Blue solenoid is energized, then it shouldbe passing a vacuum to one of the two small vacuum lines just above the acv. It should be going to the rear most of the two vacuum lines. Both those lines are within an inch or less of each other.

I'll wait for an answer before I say anything else. This is a N/A engine, right???

If its a n/a, then if you put a long piece of vacuum hose on the rear of the two metal nipples just above the acv, and suck on that vac hose while the engine is running, you should be able to close the relief valve inside the acv and stop the dumping of air. Does that work?????

So the queation I need to know, is when you talk about ***the 2"line going to the top of the ACV****** you are talking about the large hose b/t the acv and the airpump? Right?

Oversteer

The 2" line is the shortest vacuum lines that goes into the very top of the ACV

Oversteer

Almost forgot....S4 TII. The 2" vacuum line has vacuum

HAILERS

Oh. A TurboII. All bets off. It is different than the n/a acv.

I might have to go stare at my turboII acv to get this right.

Ok, I'll try without looking. The one that goes in the top of the acv is for the switching solenoid. It should have a vacuum on it at idle. It is controlled by that grey solenoid on the left side of the engine. I'll bet money that if you take a piece of vacuum hose, put it on that nipple on the acv, that you can't hold a vacuum on that nipple when sucking on it. Engine does not need to be running. That diaphram seems to get cooked and rots away.

Another metal pipe comes straight out towards you. That goes to the boost/pressure sensor.

The other two pipes control the dumping of air overboard. The one that I remember sort of in the middle and forward on the acv, is pressurized air from the airpump. It leave there, goes around to the Blue Relief solenoid, where if the solenoid is energized, the air will make a loop thru the blue solenoid and return back to the acv, at the bottom pipe on the acv. Goes to a mushroom sort of thing. There it puts pressure on a diaphram and closes the air from dumping overboard.

So if the engine is running at idle, warm/hot, take the bottom hose off the acv and see if there is pressure coming out of the vac hose going to the acv. Write back.

I don't know why I thought you had a n/a. Seems your profile said convertible??????

Oversteer

OK....regarding the vacuum line on top of the ACV...the line has vacuum...and you are correct...the diaphram is smoked!! The bad part is, I have 2 spare ACV's, and both of them are bad too!! Oh well, at least now a problem has been found. Thanks again for all your help!

HAILERS

Oversteer......yeah. Too bad. But then again, I was doing some thinking about this. So the Switching diaphram is smoked. Big deal . All that means is that air is being sent to the catalytic converter thru the split air pipe all the time. That might be a plus. Its not that much air anyway.

Now for my flub or second flub on this. Talking about the air dumping overboard. I wish I could post a schematic of the acv for a turbo, but the site won't support that. I got it all wrong about the way the turbo works. What causes the acv to dump, is pressure sent from the Relief (Blue) solenoid. That pressure OPENS the dump on the acv making it dump overboard. The acv should not get enough pressure on that bottom pipe until 3800 rpm. The solenoid (blue) is supposed to be energized keeping air from being sent to the bottom pipe of the acv until around 3800 rpm.

So it seems to me, if you take the bottom hose off the acv, the acv should stop dumping air. Its spring loaded shut. Takes air pressure to open it. No air pressure...closed.

The acv will leak a whisp of air at the dump. That seems to be normal. Try this......take a long piece of spare vacuum hose and attach it to the bottom nipple on the acv. Now blow into the vac hose. When you do, can you reach in the dump tube and feel the poppet rise up????

Try that with one of your spares. You can blow into the nipple on that mushrooms nipple and see the poppet rise up as you blow. Also when you blow into the bottom nipple, you should have backpressure. As in...no evidence of the air your blowing is leaking past the internal diaphram.

Whata ya think???? One of those acv must be good.

HAILERS

By the way. The switching diaphram in my 87turboii was toast just like yours. What I did, was take a old acv from a 82 that has been laying around, and installed its diaphram on the turboii acv. It took some metal shaping to make it fit, but it works.

That said, I'm going to buy a new one for the next emissions I have to face next DEcember.

The turbo just bakes the diaphrams.

I hope I didn't confuse you. Earlier I got it *** backwards on how the relief diaphram works in a turboii.

Oversteer

I used my compressor to blow low pressure air into the bottom of the ACV. I can hear as well as feel the valve rising. As far as the diaphram goes, I have one from an N/A motor that I can make work with a little trimming.

It sounds like there still isn't any explanation for why the O2 sensor is showing .645 volts at idle with all lines and solenoids attached. The car runs fine but gets about 13mpg. I'm still questioning if the ECU is getting the correct temperature signals from the water temp sensors in the radiator and thermostat housing. I would think that if the ECU doesn't get any signal, then the failsafe is to go rich....not lean. It would almost be in limp mode. I plan on testing the sensors and tracing their connections back to the harness to make sure.

Rob500

Thought you might like to know. I put a new O2 sensor in my car yesterday. The voltage reading at idle is now .225V

I know I have problems with my Neutral Switch. I'm going to look into that this weekend and then try smog again on monday.

Rob

HAILERS

Oversteer
If I were you, I'd get me a long piece of vacuum hose. Connect it to the metal nipple at the bottom of the acv. Start the engine and feel with your hand the air that is being dumped oberboard. Now blow into the vacuum hose to retract the valve inside the acv. Did the amount of air increase dramatically or just a little bit???????

I'm puzzled why your 02 sensor is reading high like that. If the acv was shut at idle and not dumping oberboard, then the reading of the o2 sensor should be way low, like Rob500, around .1 to .2 volts

Try stuffing something into that dump pipe and watch your meter that is tapped into the o2 sensor. Does the reading go down when the dump pipe is stopped up???? It should because your mixing fresh air into the exaust ports. If it does not, then I have a idea......but it's not pretty. In fact a sad idea. Is your engine a rebuild?

Rob500 ....sorry about intruding on your thread. Sounds like Scott was right about the o2 being shot. Just for kicks, take your Blue plug off the Relief solenoid and see what the 02 reading is (warm/hot engine).

About the neutal switch. In neutral it puts a ground on pin 1G of the ECU dropping the voltage at 1G down to less than 1.5 volts. With the shifter out of neutral, you should see 12v at pin 1G. Thats with the plug connected and the meter lead in the back of where the wire goes in the plug.