HondaCutter

I have an autometer a/f gauge and an apex turbo timer reading voltage on the o2 sensor. Sometimes the a/f gauge works right, and the tt shows the voltage fluctuating between 0 and 1 volt. But most of the time, usually after some driving, the a/f gauge stops working correctly, and the tt starts reading between approximately .5 to 1.4 volts. What would cause this, I've been through 2 o2 sensors now (both were used though) but I find it odd that both would do this. Are there any other sensors that could go bad and cause this?

I have a 92 civic dx w/97 LS motor with 95 LS ecu.
Drag 3 turbo kit, with walboro 255 lph fuel pump and vortech fmu as my fuel management.

Any help is greatly appreciated.

HondaCutter

oh yeah, I have no cat and thermal exhaust, if that helps any. And i did a search and read through 23 pages of posts and nothing. please help


[Modified by HondaCutter, 2:04 AM 11/27/2002]

HondaCutter

bump

glagola1

I would guess that the O2 sensor has been "confused" by the over abundance of either heat or fuel. Are you getting any CELs?

Do you have any idea of what your a/f ratios are like? You would need to take a dyno run with a wideband O2 sensor to know for real. Your a/f meters that run off the stock O2 are only focused on stoichiometric (.5V) and anything above or below that is seen simply as either below 14.7:1 or above 14.7:1 and not anything more specific. I hope you are not relying on either of those two gauges for your tuning.

I think those gauges are only good for finding if you car is running at stoichiometric while in closed loop. Like I said before, either your egts are so hot that they are corrupting the voltage signal or your a/f mixture is so far off that it's contaminating the sensor.

I suggest a dyno pull to get an idea of how your car is really running.

HondaCutter

what would cause my egt to raise? and no I have no CEL's, and I'm not using these for tuning, just to see if I have enough fuel at WOT. At first, I thought the autometer a/f gauge was broken, but when I hooked up the apex tt, I found that it's not the gauge...it's something else.

glagola1

I hate to break it to you but those gauges won't tell you if there is enough fuel at WOT. You could be running at 13.5:1 and they would read the same as if you were running 10:1.

Overly high egt's can be caused by lean or rich conditions or condidtions where there is too much timing advance. Basically you won't know if it's a leaning or richness that's causing the egt's until you determine such with a wideband. After you figure out where you are with your A/F in real life you will be able to use egt's as a tuning tool.

HondaCutter

but sometimes, the o2 voltage will be messed up right when I start the car, after it's been sitting all night, so the EGT's couldn't it mess it up then...could it?

glagola1

Well, the sensor won't function properly until it's warmed up and that usualy takes a minute.

If you have been running rich especially in closed loop you may foul your sensor and it won't function until the fouling has burned off.

I doubt that you car has an electrical problem that is unrelated to a/f mixture. Honda's generally have very good wiring.

PM-Performance

if its the stock o2, it wont let the gauge read correctly. plain and simple, i almsot learned that the hard way .
it will fluctuate at steady throttle and when you punch it it will always go rich whether its rich or lean . its just how they work .

glagola1

I have to disagree with itr206. The gauge will read correctly from the stock O2 sensor but like I wrote above, the stock narrow band sensor will only read a an a/f value of 14.7:1 accurately and anything above that is inacurate and anything below that is inacurate.

Do some research on how a narrow band O2 sensor works.

HondaCutter

so does this mean my fuel pressure is too high? if so, how would I adjust that with the vortech? I'm gonna check the timing and make sure that is correct. and see what happens

HondaCutter

ok, I just thought of something. I put the turbo on about two or three months ago. I didn't know I was supposed to keep a vacuum line going to the stock FPR, so it didn't have one since I did the turbo. So, could I have damaged the stock FPR by not having a vacuum line going to it? Which would cause it to run high fuel pressures all the time, right? Which would cause high EGT's, right? Does this sound...right?

98TurboRS

Try grounding your A/F gauge to your battery. This fixed the problem for me. Mine was acting like yours before I did that, now it works great.

HondaCutter

i don't think it's that... I have 2 a/f gauges and both are getting info from different sources. o2 sensor and ecu

CovertFI

are you sure it is not reading open loop and closed loop operation?

HondaCutter

what do you mean...I'm sure it is reading open and closed loop operation because that's the only 2 operations the car could be in.

HondaCutter

bump bidy bump bump bump bump bump...bump bump bump bump bump bump bump ...my mind is playing tricks on me...

HondaCutter

ok, new news!!!! I jumped my ecu to check my timing, and the ECU gave me a code 20 which is electrical load something. Which could either be my old *** battery or my cheap *** autozone alternator. would either off these cause the o2 to mess up and read the wrong voltage?

John_at_J&S

I vote with 98TurboRS. Run a separate ground wire to the batery.

Here's a check you need to do the next time it acts up. You will need a digital voltmeter and a clip lead long enough to reach the battery.

With the key on, engine not running, measure the difference in voltage, if any, between the negative terminal of the battery and the place where your O2 meter is now grounded. It should be 0 volts.

Start the car, and turn on the lights, the stereo, and the AC, and look for a change.

If there is any difference, you will need to run a separate ground wire to the battery.

HondaCutter

read the post above your last post. what's your opinion on that?

HondaCutter

bump