von

Hello everyone. Wile racing someone on the freeway with my new 12lb flywheel I noticed that my engine stalled wile out of gear after the race. I noticed the engine turned right off really fast. I started it up fine but is harder to start. It stalled again so I pulled over and looked under the car and noticed the oxygen wire is fried and the Oxygen Sensor itself is black ? So Im guessing not only did it burn but also Shorted against my new chrome header.

My ? is will the fuged up Oxy Sensor make me stall???

Most important ? is may I have gotton some Fucked up A/F ratios when it started shorting causing detonation?

Ramocheese

If you are looking at a basic a/f ratio gauge, it pulls its reading right off the O2 sensor. If the wires are melted or shorted out, your gauge would get a bad reading, as well as the ECU.

I don't have a rotary yet myself so I can't answer for rx-7's in particular, but in most cars if the O2 sensor goes bad, or if the ECU does not get a reading from it, the car will go into a limp mode and run very very rich

hope that helps

von

Very very rich is good

Scott 89t2

that's one down side of the lightweight flywheel. rev your engine up and the rpm's drop too fast and the ecu can't catch and it'll just stall... you might need to raise your idle.

o2 won't effect idle.

edit: it should still start and idle fine... I'm talking about when the rpms are high and just drop. like sticking the clutch in at 3000rpm while rolling to a stop. the light flywheel can stall it out.

HAILERS

That's cool. A object that generates millivolts has fried a wire. Outstanding. Well done.

von

The Oxygen Wire Melted on the RB header...For some reason HAILERS it turned the Oxygen sensor BLACK. . Is this fried or did I just run over some mud???

madas7

you'll probably find that your new found header was the one that ate your o2 swnsor wire....

von

What about the BLACK OXYGEN SENSOR?

Heat Tranfusion Mabey ???

So far I have understood that No Oxygen Sensor = Rich?

What I didnt mention is that I heard massive amounts of Pinging but thought it could have been something else. This happend right whenI started smelling somehtng melting.

von

Hailers .....MILIVOLTS??? How come My S-AFC reads 3.8V

???

von

Nobody seems to understand what im talking about.

1/ I heard pinging

2/ The Oxy Sensor reads enoughf volts to fry the ECU im sure

3/ The Oxygen Sensor is covered with black mud

Icemark

The "black mud" on the O2 sensor, this is just the color or you really have melted something all over it???

The output of the ECU for the O2 sensor is buffered and can have a direct short to ground and not effect anything. How the output works is it sends a voltage signal (less than 5 volts at less than 50mA), and depending on continuity to ground, interpets how much continuity. The O2 sensor simply allows more or less continuity to ground based on how much Oxy it sees in the exhaust at operating temps. Furthermore in the ECU it would set and error code and bypass that monitoring.

So the output of the ECU can do nothing to the O2 sensor... there is not enough mA. Any discoloring of the sensor is probably from heat or a protective coating tht was not removed.

It would be possible however for the shorted wire to cause the ECU to read a too rich or too lean situation (I don't know which, Reted might).

von

well someone please let me know how possibly LEAN because I swere I heard detonation and thier should be no reason why my car doesent idle.

THE car dies at idle not just when I blinp it.

After the flywheel was installed I feel no difference in idle or idle after I blimp it. My proof is what I noticed before and after instalment.

HAILERS

Here's a little write up by a fellow : http://www.teamfc3s.org/info/articles/o2sensor.html

As you can see, if it were a stock/replacement 02 sensor, it can't fry any wires. The sensor is the creator of the voltage through a chemical reaction. Less than a volt. But if you have a gauge of some sort, that could be what fried the 02 wire through a short of some kind.

Also when the pedal is under full throttle, the 02 sensor has no effect on the air/fuel mixture. Only at low throttle.

It sounds like you have a aftermarket 02 gauge and maybe sensor. That's the only way I see you ever getting three volts like you said.

It's pretty easy to find out if the 02 circuit to the ECU is working or not. Get a Bosch sensor. Install it. Put you negative lead of your digital meter on ground and the positive on the 02 output. Make sure the 02 wire is going to the ECU. Then go drive the car at a steady fifty mph or sixty mph. The digital meter should show a readout that jumps above and below 4 mv. It's jumping around because the ECU is making corrections to the air fuel mixture, and that shows up on the output of the 02 sensor.

Now go full throttle. The meter will go to perhaps 7 or 8 mv. And will be steady. That means the ECU is now in open loop and the 02 sensor is having no effect on the air fuel mixture. It does not jump up and down anymore til you let off the throttle.

Prior to getting a Wide Band 02 sensor from OZ, I used to tap into my 02 output wire with a cheap digital meter from RS, and use that as a air/fuel meter. Seemed more accurate than blinking lights.To me anyway.

You did not say when the knocking happen. Whether at full throttle or light throttle. I'd suspect cheap gas myself, either way.

That's just gotta be a aftermarket 02 sensor of some kind you have. That's the only explanation for the remark about three volts.

So bump this to the top.

HAILERS

Timing that is toooo far advanced will cause knocking.

jeremy

iTrader: (1)

curious as to the pinging noise as in a piston this is the pistonhead smacking the bore as it gets forced down against the crank.

Bambam7

It's pre-ignition... the sound of a charge igniting as it's compressing.
Anyways.... you were racing on the highway, you heard detonation.
Ok, well, if you leaned out for some reason, it will ping, make your exhaust KILLER hot, melt the o2 sensor wire, (only beacuse it's in a hot area, NOT becase of any current) The max it will ever read is 1v. You very well could have blown an apex seal, that's why it's hard to start and won't idle right now.
You could have a big vacuum leak causeing the bad idle too...
Black o2 sensor, on the outside you mean?? Who knows.. probably because of the heat from the header, because of the lean/hot mixture!! Sounds like it all makes sense to me!

Do a compression test my friend!!!!!!!!
I'd be sortof worried.
That's how I blew my engine, after a lean run on the highway... pulled off at a ramp, and it was idling lumpy, and is hard to start.

Icemark

Hey Von, the other thing to remember is that the O2 sensor is not monitored during WOT.

TurboIITom

A vacuum hose may have cracked... on my TII when a vacuum hose split open my rpm at idle dropped to 100 rpm and the engine stalled if I wasn't in gear and on the throttle. And my O2 sensor has never been plugged, when I bought my car the o2 wire was cut and i had no idea where it went and the car ran just fine. I got a new bosch sensor now... not installed yet.

trbospd

I had the same thing happen while just busting on the throttle at a red light. The large hose for the boost bypass valve popped off under high boost. The pinging noise I heard was from the line being off under boost and also letting off the throttle. It also killed at idle after that but started up quickly only to die again if I didn't hold the throttle open.

Check your hoses dude!!!

Cheers!

answering a question for someone who has more posts then me seems odd. FWIW, you can does not use the o2 sensor during WOT (ie racing) the only time the car's ECU uses a o2 reading is during closed loop operation for fuel economy. Ie crusing down the highway to the cottage at 75 mph or whatever.

Having the wire fry is not too uncommon. if it came into contact with your header or downpipe (turbo) it will melt the insulation and maybe even melt the wwire itself.

To remedy your problem about the stalling if you blip your gas pedal and the car stalls cuz of the light weigth flywheel... goto teh FSM and look up the pins for the ECU. Make it think the AC is on all the time even though you may not have one... this will cause the ECU to give the engine a little more gas thinking there was load on teh engine.

If it isn't stalling for that reason... i would check compression on your front and rear rotor. Check fuel lines... etc.

von

Ok thnx guys and I think I found some causes upon closer inspection. First off cheers I have a S-AFC so I dont think I would need to do that A/C thing but great idea anyways

Another thing is my S-AFC reads 3.8v hailers not 3

I knew the wire rubber was burnt from the header and not a short.

The Oxygen Sensor was black because the mechanic forgot to take off the black electrical tape he put on it and it just melted on thier making it look toasted(it was dark when I looked at it)

I used 711 gas and my timing is only slightly advaned I think. Its just alittle above the middle of the DIS.

The next morning I started the car and it idled fine without dying. I had to readjust the idle though wich I did after the reinstalation of the oxygen sensor...My guess is something about the ECU giong into limp mode causing it to die right away because it went into limp mode at such high rpms it didnt know what was up.

Yes I was racing full throttle when I heard all this crazy gurgling **** from the engine but I kept on the gas anyways so I can be sure. Right now the car idles at a steady 800 rpms +- 20rpms and has power but I know that when you ping an N/A It doesent always show up right away. Anwyays im getting it dynoes again next week to see wher its at.