When I got my 87 TII fc the previous owner said he had eliminated all the emissions. I knew less about rotary engines back then and still dont know as much as I would like to so I was just like ok whatever. The car has hot start problems and idles strangely (sometimes it stays at the same idle and sometimes it bounces about 500 rpm then bogs down). Other than that it runs fine, there is no lack of power or anything. But today I noticed the o2 sensor isnt wired to anything, it's just bolted into the down pipe. Is that part of the emissions removal or could that be one of my major problems? I dont know about this car but I know with the piston engines I have had if you dont have an 02 but still have the stock ecu the car will run like complete ****. Is it the same with this car and should I wire up a new o2 asap or will it be fine? Thanks

 

Yea, Rewire it. The car needs it to run correctly. Also you'll get horrible gas milage, not too mention poor performace w/o one.

 

However it won't harm anything. It doesn't even throw a check engine light. It is obviously beneficial piece seeing as it will better regulate fuel, but it isn't disaster by any stretch. I have friends that haven't had theirs wired up for years. I personally ran with a useless one for a while just because I was cheap and lazy.

 

Do you guy's think that no o2 along with the idle being set at like 1200 rpm could contribute to flooding issues? I'm also getting about 6-10mpg right now with pretty much no mods to the engine. Hopefully putting in a new o2 and adjusting the idle will help. Also the bouncing idle problem is really weird. It was doing well after I put on a new turbo intake boot but all of a sudden the other night I started it up and it started bouncing (I still drove it back home). I did take it close to red line a few times on the way home but I dont think that would be a problem and it was doing it prior to that. The idle will go from about 1200 rpm to 1700 then back down to 1200(the idle isnt adjusted properly). I was thinking it's a vacuum leak somewhere but I dont see anything loose or off and the previous owner said it has all new vacuum hoses.

 

02 only works in closed loop. Closed loop is only available while driving at a steady speed. It has NO effect on idle at all.

That said, it takes but a moment to reconnect the 02 sensor. In closed loop it will trim the fuel to an approx 14.7afr ratio for better fuel economy.

http://www.teamfc3s.org/info/articles/idle.html

Also, next time the engine is hot, and the idle is around 1200rpm, just go pull the BAC's elect plug off and see it anything happens. If nothing happens, then just go about your business. It's no BAC related then. Idle is too high though. Vacuum leak or more likely the turbo inlet/outlet ducts are leaking.

 

I'm not sure but I think the bac valve was removed and has a block off plate to cover it up now. Could the sealant used to seal it have a leak in it? Could that cause the idle issue? Here is a pic.


So the o2 has nothing to do with the idle but could it be playing into my hot start issue? The hot start issue is whats bothering me the most. This is my track car so I dont really mind shitty gas mileage but if the car dies on track and I cant restart it, thats whats worrying me the most.

Also with a bad turbo inlet or outlet duct, if that is the problem would driving with it in it's condition, would that cause internal damage to the engine? I'm not really worried about things breaking but I would like to make an event in april and after that the car will probably be ripped apart and be rebuilt.

EDIT: Oh and how do you adjust the idle without the bac valve on the upper intake manifold? I know there is a way with that removed but cant find it when i search.

 

Most people say they disconnected theirs and only lost 2mpg. You can lose more with a faulty O2 sensor that's still connected, though. It helps and you should get one but the car should still be perfectly driveable without it. The car only relies on the O2 sensor when you're cruising steadily and even then it isn't essential.

Dunno why a piston would have any problems either. Maybe newer cars slow down the car as a safety precaution or something.

 

Hello,

Not to post *****, but I tried putting an o2 sensor in my NA car today that previously did not have one. Someone previously stole the sensor, so I figured I'd get one and put it in. But when I tried looking for an electrical connector to match the sensor, I was dumbfounded!!! WHERE IS THE PLUG THAT THE O2 SENSOR PLUGS IN AT?

My Turbo car has Megasquirt, which somehow doesn't use an O2 sensor, and I couldn't find a spot to plug in an O2 on that car either.

Thanks in advance,

Vincent

 

should be on the stock harness there somwhere...im running microtech LT8 and i dont got no 02 sensor either.

 

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EDIT: Oh and how do you adjust the idle without the bac valve on the upper intake manifold? I know there is a way with that removed but cant find it when i search.[/QUOTE]


The attached jpg is looking fwd at the throttle body from the rear. The throttle stop screw has a 8mm jamnut on it and the tip of the screw rests on the throttle linkage. Adjusting the screw moves the throttle plates open more or lets the plates close more.

Although the screw is not shown in that jpg, where I pointed is where it is. The intercooler has to be removed to see/adjust it.

Low comperssion, leaking injectors, bad timing , no BAC all contribute to a difficult start of a hot engine. This is getting tiresome for me and everybody who reads it, but....................the ECU uses an internal fuel map for Starting. It does not use the afm at all duing Starting. This preset fuel map is too rich for the conditions I listed above. So you want to LOSE that internal fuel map duing Starting. If you LOSE that internal fuel map, then the ECU has to use the afm for fuel delivery. The amount of fuel is much less using the afm during Start.

How to lose the START fuel map of the ECU.........................depin the wire in the 3B location of the small plug of the ECU. Done.

But, if you leave it disconnected all the time, then COLD starting will be more difficult because not enough fuel will be delivered durning cold starts. But if you live in HAWAII or Florida, mabe this will not be a problem because it does not get that cold there. Guessing

There are two jpg of a Palm attached. In the bottom, left hand side of each display is the pulse width during starting. The first jpg is the pulse width with 3B connected during start, the second jpg is with 3B disconnected during start. Which has the smaller amount of fuel during Start???? Yes, that one.

 

HAILERS,

what do you think about disconnecting the O2 completely or using a switch to control O2 sensor use?

My main thought is to turn the O2 sensor off and remove fuiel to right before the engine stumbling point, achieving a lean burn so to speak. I had this idea after reading about the Honda Insight's lean burn mode @ 22:1. I had previously tried to remove as much fuel as I could but I think the O2 sensor kept telling the ECU to add fuel back in. Could you gain better fuel efficiency at cruise by going leaner than 14.7:1 with this method?

 

Hailers,

So with that said could you just wire in a switch to the 3b pin? Open during hot start and closed during cold start? In the end it is the same result as dissconnecting it but with the added abilty to reconnect if cold starting is an issue.

 

There's no good reason to remove the O2 sensor, there are no benefits to doing so. However doing so will cause zero problems other than increased emissions and slightly higher fuel consumption (~5% depending on how much highway driving you do).

That's completely untrue.

No, not at all.

Nope, there is no way such high fuel consumption is being caused by either of those things. Either you're driving everywhere like a lunatic, or there's something else wrong with your engine.

Most likely that, or the idle speed is set to high or the TPS isn't set correctly. It could even be a combination of all three.

Absolutely, fix that ASAP.

No, the O2 sensor is only used during light-load cruising. No other time.

Low compression and/or leaky injectors. Those two things are the cause of nearly all hot-start flooding issues.

Adjust the throttle stop screw.

I think it would be silly to not do that. The ECU's start signal is there for a reason, so disabling it completely isn't wise.

That's complete BS. It is not needed for the engine to run correctly, mileage will only decrease slightly, and performance will be completely unaffected. How do you think engines ran before O2 sensors were invented? Oh right, they ran fine. It's pretty obvious you just made all that up as opposed to basing your comments on actual experience.

I doubt anyone would ever lose that much. I was getting 14.5mpg from my FC, and if that dropped to 12.5mpg that's a 16% increase in fuel consumption. That a massive difference, and the O2 sensor simply doesn't have that much effect on determining fuelling.

 

not to be an *** but i've had more that a few older car including the rx-7 and if the o2 sensor was bad a new one always helped my MPG more than enough to be worth the money. Maybe some of you are less affected by the o2 becuase you spend less time in closed loop, however if you drive alot of highway miles at a steady speed (closed loop) than the o2 should help mpg, **** gas is 3 a gallon and an o2 sensor is like 20 bucks if you get 1/2 a mpg its worth it

 

Ok, you go as far to say that its complete BS, then you state, if I read correctly, that w/o one you get a 16% (or is it 5%) increase in fuel consumption? Does the car just 'run fine' when your dumping 16% or 5% more fuel in the motor than it should? Is this going to create drivability issues? Is this going affect emissions? Is this going to foul your spark plugs? Is this going create poor perfomance? Probably.

I've had cars w/ bad o2 sensors, I've known people to drive cars w/ bad o2 sensors. Do the cars drive? Yes. Do the engines run great. No. Could be a combination of problems, but none the less I think "If the car came w/ it and the ecu uses it to base fueling calculations that you should probably have it hooked up."

Carbureted engines are different. Ways to check carburetor mixture adjustment include: measuring the carbon monoxide, hydrocarbon, and oxygen content of the exhaust using a gas analyzer, or directly viewing the colour of the flame in the combustion chamber through a special glass-bodied spark plug sold under the name "Colortune" for this purpose. The flame colour of stoichiometric burning is described as a "bunsen blue", turning to yellow if the mixture is rich and whitish-blue if too lean.

The mixture can also be judged after engine running by the state and color of the spark plugs: black, dry sooty plugs indicate a too rich mixture, white to light gray deposits on the plugs indicate a lean mixture. The correct color should be a brownish gray.

That is all... good luck running no O2 sensor, because According to
NZConvertible it will 'run fine'.

 

I like this guy. Finally someone that actually knows what they are talking about.

 

On occasion I run my car(s) with no 02 sensor connected. I also have a wideband 02 sensor/controller from Zeitronix to monitor the afr. I'm here to witness that the 02 sensor not connected up, does not make that big a difference, even at cruise. There is a difference, but not large.

I'm talking about having the 02 sensor connected and seeing it trim the afr to 14.7afr, and then having the 02 sensor disconnected and seeing afr in the 14.2 to 14.6 afr under the same driving conditions.

I guarantee having it disconnected does nothing to effect the driveability of the engine/car. None. You'd never notice if the connector fell off.

It does give slightly better mpg (frankly I don't go around measuring mpg, it's not productive). And it will help the converter perform better in that it is a Known, that the converter is more efficient when the mixture entering it is in the 14.7 afr range.
Or as the Training Manual for the RX-7, that is free, and online, says: *The objective is to use the catalytic converter at the highest level of efficiency to reduce CO, HC and NOX emissions*. See page 4-42 and the previous page that lists the corrections the ECU makes to the fuel delivery and what they are.

The 02 only works in closed loop. If your acceleratiing it's not being used by the ECU at all. If idling its not being used by the ECU. If your driving along above about 17-20 mph and easy on the pedal it'll go into closed loop and trim the fuel to the 14.7afr.

Drive along over approx 3500rpm, the ECU won't go into closed loop at all. It's out of the picture above 3500 rpm. Any gear.

Finally someone who knows what he's talking about. Me. humor......

 

my o2 sensor wasnt connected for maybe 2 years until i noticed it then i saved maybe a couple of gallons of fuel.....

 

You're absolutely right, that's why I say there's no good reason to not have one. Based on my measured fuel consumption running with and without one, I paid off the cost of the new O2 sensor in about 5 months. My FC is a daily driver with mixed urban/highway driving, so a car that's only driven on weekends will take a lot longer than that, and one driven regularly and mostly on the highly will take less time.

Go back and read it again, I said ~5%. That number is based on my own measured fuel consumption. And it wasn't one tank with an old sensor and one tank with a new one. It was three months with no O2 sensor at all, and then three months with a new one.

It will do none of those things. Again, you're not speaking from experience, I am. While driving, you cannot tell if the O2 sensor is disconnected or not. The O2 sensor is only used during light-throttle cruising, and is ignored as soon as you open the throttle or go over ~4000rpm. So how could performance be affected if the O2 sensor play no part during "performance" driving?

I agree that if should be hooked up, and I also agree that whatever problems you had were caused by other faults. You're very wrong when you say "the ECU uses it to base fueling calculations". The O2 sensor is only used for mixture trimming (not base calculations) and only under certain limited conditions.

Who mentioned carb'd engines? If you mean the older engines I referred to, I was talking about older EFI engines that had no O2 sensor or closed loop operation. There were many of them, including some FC's...

 

is it just me or does it look like your strut isnt all the way bolted on?

 

What about trimming the fuel down with a fuel controller and no O2 sensor? Would that allow for better mileage?

 

Better mileage but worse emissions, which may or may not bother you. The reason the ECU aims for stoichiometric mixtures at cruise is not specifically to reduce fuel consumption, but because that's where emissions are the least.

 

ic.......well, since i have no cat, emissions doesn't seem to really apply. Sounds like a new experiment for next trip.

 

I've had the same problem on my car, (erratic idle) and my bac valve has been removed along with all the emission ****, i did not do this, i bought the car like that. It is also a TII, with the same block plates. My o2 sensor is not hooked up either. anyways my car will run fine, excpet at idle, but can anyone offer sound advice to actually help both of us ? specifically with the erratic idle, ive tried soo much ****.
thanks

 

I think your problem is the metal pipe after the turbo has a huge open connection into it. If you seal up that opening I think that will fix your idle issues