02's, codes & mileage

jaymac · Aug 4, 2005

Can 02's affect you mileage (20 mpg down to 12) w/o throwing a code??

HISSIN50 · Aug 4, 2005

I would not quite expect that much milage degredation. I would look for other things (I know you have been). It seems like 3-4 MPG is a good increase upon installing new ones if the old ones were shot. I could be wrong though.

Good luck bud.

jaymac · Aug 4, 2005

Techincally, my fuel level sender is broken. As sson as I put in 1 gallon of gas, it goes to the tippity top of the guage, almost out of view. Then, after awhile (about 50 miles on 4 gal.), it will make it's way down to the 1/8 tank merk in about 5 minutes. So that would work out to 512.5 mpg, IF that gauge is "accurately broken". That 1/8 might not be 1/8, but maybe it is. A new sender is $82, and that's crap
I want to re-check the ground strap for the injector harness.
Also, how often should wires be replaced. I have MSD super conductors on there now, close to 2 yrs. old, as well as the cap and rotor. Time for new ones?
The ECT sensor did fix the Hot Start problem, but I only drove 38 miles w/ the new one, and 12 w/ the crap one, and the gas needle just started coming down before I got home, so I can't tell yet if it's helping mileage.

So is it time to replace cap and rotor and wires? I don't think I EVER replaced te 02's since owning the car (almost 2 years). Tune up time?

HISSIN50 · Aug 4, 2005

I am sure you know to fill it up, drive it. Fill up again and note the milage change from the last fill-up (dont need a gauge for that). That is the only real way to know.

I do plug wires by feel. If they dont ohm out well or are leaking, I replace them. I would think those wires should be alright (they are fairly robust).

Making sure the HEGO ground is attached at the back of the motor is good - that helps the O2's light off faster, which helps milage.
Good luck bud.

jaymac · Aug 4, 2005

"HEGO"?
I replaced the ground strap from the head to the firewall with a big 0 ga wire while trying to track down my H/I swap "no starting" demons. So what's the HEGO ground all about - the same one as the fuel injector harness?

See, sometimes it's the logical things that escape you, like checking mileage in reverse - top to middle, instead of middle to bottom. Genius, pure genius!!
That's why I keep you around.
Thanks, JT!

HISSIN50 · Aug 4, 2005

jaymac said:
"HEGO"?
I replaced the ground strap from the head to the firewall with a big 0 ga wire while trying to track down my H/I swap "no starting" demons. So what's the HEGO ground all about - the same one as the fuel injector harness?

See, sometimes it's the logical things that escape you, like checking mileage in reverse - top to middle, instead of middle to bottom. Genius, pure genius!!
That's why I keep you around.
Thanks, JT!

Glad I am useful for something.

HEGO = Heated O2. As opposed to EGO's, which are something shrinks talk about, or are non-heated O2's.
We have HEGO's (and some folks with HEGO's have egos too ). HEGO's light off really fast (30-120 seconds after cold start-up) because they are self heating. That is why they cost more, but also last longer.

There is a ground wire for the HEGOs that attached to the back of the lower intake IIRC. It sometimes get left off in the course of repairs.

Good luck bud.

jaymac · Aug 5, 2005

excuse my ignorance again (I find myself saying that alot )
IIRC?

jaymac · Aug 5, 2005

IIRC = "if I remember correctly"? did I get it?
HEGO= "Heated Exhaust Gas Oxygen" Is that it??
I just need some time to think,. sometimes!!
Anyway, I don't remember any connecting a ground strap to the lower intake, so might you be able to tell me where this strap would originate, or to which specific bolt on the intake it would attach, or both (as we all know how hard it is to see/reach behind the lower intake!!)

jaymac · Aug 5, 2005

jrichker · Aug 5, 2005

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage.

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

HISSIN50 · Aug 5, 2005

jaymac said:
IIRC = "if I remember correctly"? did I get it?
HEGO= "Heated Exhaust Gas Oxygen" Is that it??
I just need some time to think,. sometimes!!
Anyway, I don't remember any connecting a ground strap to the lower intake, so might you be able to tell me where this strap would originate, or to which specific bolt on the intake it would attach, or both (as we all know how hard it is to see/reach behind the lower intake!!)

You got it with the acronyms. Sorry about that.

JR has info in the last paragraph of his last post about the HEGO ground. That is actually as much as I recall (actually more - I knew the wire was orange, but could not recall if it had a stripe - obviously per JR's post, nope).

I remember seeing mine when viewed from the pass side, but I did not play with it. It should kind of stand out as I recall. Sorry to not have more info. Good luck bud.

jaymac · Aug 7, 2005

Is that orange wire from the FI harness the only one coming from the harness to a ground, cuz if it is, I believe I already have it grounded, with the strap coming from the head to the firewall.
I'll double check for color.

vristang · Aug 7, 2005

jaymac said:
Is that orange wire from the FI harness the only one coming from the harness to a ground, cuz if it is, I believe I already have it grounded, with the strap coming from the head to the firewall.
I'll double check for color.

If it helps here is what I have...
There is a grounding strap that runs from the head to the firewall. There is also a ground wire that comes out of the efi wire bundle. I have both of them bolted onto the back of the intake. I don't remember the color though. I'm not sure if this is what your asking about, but I hope it helps.

jaymac · Aug 9, 2005

HISSIN50 said:
I am sure you know to fill it up, drive it. Fill up again and note the milage change from the last fill-up (dont need a gauge for that). That is the only real way to know.

Today is the official "try the above technique" day.
The first report.
Once my gas gauge made its' descent from full to the 1st white line above the red "empty" line, I filled it up.
It took 11.8 gallons to shut off.
That means there were already 3.6 gallons in the tank.
By my calculations, There should only be baout 1.5 gallons in the tank at that line on the gauge. It is no secret that my sender is broken, but I thought the "bottom of the tank" measurements were at least correct.
Guess not!
Another 10 miles I will fill it up, see how many galloms it takes, and divide that into the miles I've driven, and "viola!". Accurate mpg measurement!
Thanks JT

HISSIN50 · Aug 9, 2005

jaymac said:
There should only be baout 1.5 gallons in the tank at that line on the gauge. It is no secret that my sender is broken, but I thought the "bottom of the tank" measurements were at least correct.
Guess not!

Sounds good Jeremy.

I know you were expecting this. The fuel gauge, being not as important as oil pressure and coolant temps, is not quite as accurate as those two.

jaymac · Aug 9, 2005

Turn of events:
I'm not expecting the most phenomenal mileage results, as I had to do some hauling ass today when I got a cal from my fiance that her tire exploded on the highway and she was stranded and freaking out.
Oh well, I'l re-fill and check tomorrow...

HISSIN50 · Aug 9, 2005

Her being ok is the only thing that matters.
After something like that, I would say Milage-smilage. Who cares.

jaymac · Aug 9, 2005

Well said!
It could've been much worse, and I had to give her the same relity check wen she was upset about not being to wrok on time tomorrow because of it.
We are lucky indeed
I did, however, score a new breaker bar and deep 3/4 and tire press. gauge out of the deal too

jaymac · Aug 10, 2005

OK, update:
Used 11.9 gal. to fill up. Today I put in 5.2 gal to fill it up again. I had driven 93 miles.
So, 93 divided by 5.2 = 17.9, is that the correct equation?
So, mostly stop & go city w/ some 3200 RPM highway duty to rescue the fiance, and ~18 mpg?? Not really that bad after all, is it?

jaymac · Aug 10, 2005

I'll prob end up replacing the fuel leel sending unit anyway, cuz it freaks me out seeing the "empty" vicinity, and I'm not gonna drive around w/ a full tank of gas every day, cuz more gas=more weight=decreased mileage.

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