Rob500

Anybody know what the O2 Sensor output voltage is supposed to be with the car idleing in neutral. Mine is .03 to .06 volts. Which is essentially zero. Is this OK or is the sensor shot?

Also I can unplug it with the car in neutral and I don't get any ecu codes. Does the ecu only reference the O2 sensor when the car is in gear?

Rob

Turbonut

iTrader: (1)

O2 sensor inoperative @ idle. No feedback needed. If it remained disconnected while on highway, check engine light would then come on.

Rob500

Is it the neutral switch that suspends the feedback process? Again with zero output at idle, is the O2 sensor shot?

Rob

HAILERS

The O2 sensor is working its butt off all the time. It's true that it's not in the LOOP so to speak at idle, but it is putting out.

The extremely low reading (assuming you have a fully functional car) is due to the acv pumping fresh air intot he exaust ports at idle. The 02 sees a very lean mixture when that happens.

Just to show you what I mean, take your airpump belt off and then look at your 02 sensors output. I guarantee a figure like .7 or .8 volts at idle.

I used to have a meter hooked up to the output of the O2 sensor all the time and never saw more than .8 volts output

So do as I suggested and also go for a drive on the hwy and see what the reading is. Should bounce wildely on either side of approx 0.4 volts

nonameo

acv is for emissions right?

HAILERS

ACV is for emissions.

Ouch. There is a easier way to get the reading from the 02 sensor to show higher at idle than taking the airpump belt off.

Instead, just pull the Blue connector off its solenoid on the left side of the engine. That should make the relief valve in the acv dump most of the air overboard, which in turn makes the mixture at the 02 sensor richer which makes the voltage go up. Fully warm car when you do this. Cold cars don't count.

Turbonut

iTrader: (1)

Great explanation as usual. I'm going to start capturing all of Hailers' replies. I'll never need to ask another question. They're better than any shop manual!!

HAILERS

Better be careful there. I've, shall we say, made an error or two in the past. I'm glad someone can finger out what I'm saying. Sometimes I'll see an old post and even I wonder at what I meant. humor

Rob500

What suspends the feedback function at idle? Is it the Neutral Switch?

Rob

SureShot

ECU magic!

HAILERS

*****What suspends the feedback function at idle? Is it the Neutral Switch*******

Sorry, I don't know. I suspect it's the tps and maybe the tps plus the pressure sensor plus the neutral switch. I've never seen a written word on that subject. I suspect a combination of things.

You know of course that it goes out of the loop when acclerating also? It does. I found recently that on a level road, in fifth gear, I can get to about 80mph before it goes out of the loop. I think it was around 70mph in forth that it went out of the loop(I forget the exact figure). So thats why I think its pressure/boost sensor plus tps related.

Rob500

Thanks I really appreciate your help. I'm trying to pass emmissions here in California. We have to do a two speed dyno test. I pass the visual, all my emmissions stuff is intact. I pass the 15 mph test. I fail the 25 mph test by 14 ppm hc (105 vs 91 allowed). My hc at idle is about 20 ppm. I've done a tune up, cleaned my air filter etc. Now I'm trying to find out why hc's are high. I thought my O2 sensor might be bad. I just need to get the hc's down a little bit.

I've checked the resistance values on the tps and the value of the high range sensor at idle seems to be out of spec (.5 vs .6 k ohms). My car has a 300 rpm lump in the throttle at 1500 rpm.

Rob

HAILERS

First make sure that your ACV is not dumping big time overboard at that large hose at the bottom. Yours probably isn't since you passed the 15mph test, but check it anyway. You probably have a whisp of air at idle but it shouldn't be big time dumping.

I really am not into cheating on this but........there are two solenoids on the acv. The rear one is for the Split Air pipe(Split Air Solenoid) that goes to the catalytic converter. It has come to my attention that is one is real careful, he can remove the solenoid with a 19mm box end wrench, being real careful not to drop the tiny little poppet valve and its spring. Then reinsert the solenoid without the poppet and spring.

This dramatically increases the flow of air to the catalytic converter. I observed this by submerging the pipe that enters the catalytic converter into a pail of water and watching the bubbles (had to remove the grey switching solenoid plug to see that).

I assume you set your timing right on the mark, changed spark plugs, changed the oil (I have no idea why I included that), made sure the acv wasn't dumping overboard at idle (shouldn't dump until 3800 rpm, way below your 25mph check) and the tps set.

HAILERS

About that tps. I'm pretty sure that isn't screwing things up for you. I'd be interested in the Narrow Range more than the Full Range. Attached is a picture out of the fsm. What I'd do is get a digital meter (cheap is fine, expensive is also fine) and put the negative lead on a good ground, then the positive in the back of the TPS plug itself (plug connected up, nothing unconnected) and read the output on pin *A* at idle. Turn the TPS screw until you read *1* one volt plus or minus .05.

Do that with a HOT engine and with the engine at idle. Do not do that with a cold engine. Sorry, I don't have the color of the wire at pin *A*. I have no wiring schematic for that year.

Rob500

We've run it in a Pre-Test mode and it looks real good (hc's around 40-50ppm). But when we try to do the real thing it fails. Apparently there is more resistance on the dyno. They have to do the 25mph test in 3rd gear to keep the rpm's in range. On my car this is about 2100 rpm. So I think they're bogging my car down. The FSM says that under load the secondary injectors come in. Maybe that's happening. But I'm not sure about 2100 rpm. Ive got a litte bit of an irregular misfire in that range also. That could be putting me over too.

Rob

HAILERS

You might also check your high range the same way. See this chart from the manual:


See where it says approx 0.8 volts at idle for the Full Range????? And where it say approx 1 volt for the Narrow Range???????

For right now concentrate on the Narrow Range where you see one volt at idle with a fully warm (hot) engine.

Make sure the car is fully warmed up at the inspection station. Leave the car idling if you have a long line of people in front of you.

There's always the chance that the catalytic converter is getting old giving you problems.

Rob500

Re your comment on the tps. The narrow range values are good. I've used the two lamp method to try to adjust the tps with marginal results. I've got the same fsm and a good multi-meter. I'll try your suggestion.

Rob

HAILERS

The secondarys don't come on line until 3800 rpm and then only under load. I can be running on a level road over 3800 and they won't come on line as long I ease the throttle over 3800.

In Ft Worth we do the emissions using rollers also at two speeds. Like this :

Rob500

New Catalytic converter. I still have two cats.

If the narrow range voltage values are checked on pin A. Which pin should I check for the high range voltage values?

HAILERS

Full range would be on pin E. Usually the Mazda people look into and count by looking into the rear of the plug, where the wires enter the plug. See the first picture I sent.

Hey! I just noticed on the emissions report on the 87 they have my car down as a Automatic! I don't drive no darn Automatic, never have, never will (well maybe if its a Mercedes or Ferrari, throw in a Viper).

HAILERS

I really have nothing against the two light method. I can take it or leave it. Just make sure that your using leds and not some lights out of a tail light.

I've set the tps using the lights and then checked the voltage output. Guess what. It's always 1 volt plus or minus .05 after setting using the lights. I just use the meter because its handy. Either way is just fine.

Rob500

Looking at your report you have a lot more O2% than I do. Mine is only .61 at 15 mph and .50 at 25 mph. All the other readings are similar.


I'm going to have to look into the acv valve. Can't do that until the weekend though.

HAILERS

Well I seem to have screwed the pooch on the tps. As you know I don't have a two plunger tps. I have a series four with only one plunger. I gave you the wrong pins (letters) to look at. Read this thread by Keith(Irv) and you'll see what I mean https://www.rx7club.com/forum/showth...threadid=14368

But if you set it using the two light method that should have been fine. But out of curiosity, you might check the output of the Narrow range with a hot engine. Just for grins.

Rob500

You mention two solinoids on the acv. I just went out to the parking lot look at the car. The rear one is also underneath the acv. If that is correct, it looks like it would be very difficult to get a wrench on it to take it out. I'll have to check that out later also.

Rob

HAILERS

What I do is disconnect the electrical plug. Then put the plug thru the box wrench and slide the wrench on the solenoid. You just need to break it loose and it'll spin loose. Be sure to cup your hand under the solenoid as you uncrew it in case the poppet and spring fall to the ground. Takes a 19mm box end wrench. Socket won't work, no way.

I've had a moment to reflect on the tps. I was right the first time about the pins. Its the wipers output you should look at. Pin A for the narrow range and pin E for the Full range. No doubt at all.

You can figure out which these are by looking at the jpg I attached showing the wire side of the harness plug that attaches to the tps plug. Just to be sure, I am not talking about the green check connector, I'm talking about the tps plug. I know you know that, but what if??