Thread: Regrounding the O2 Sensor

why is this thread 14 pages long lol

where are you guys ohming your meters from? i measured from my ssac stainless steel header o2 bung to the engine block as well as the negative terminal on the battery and registered close to 0 ohms. interesting theory however i can't reproduce your findings??? is there only 1 person that actually measured resistance here aside from myself?

What kind of meter are you using? I used my Fluke to measure and noticed a slight change in resistance but even that is not accurate. You need to use some thing more accurate like a LCR or a meter that will go into the mili ohms to see the things we are looking for. Most meters only display in the 100's of mili ohms and that is rounded out. You will not see this with a normal meter. A couple hundred mili ohms can create a voltage drop that will affect how the sensor gets the signal to the ECU.

Its long due to the lenghty discussions, explainations, trial/errors, results, and off topic questions... Like this one..



Discussed very early in this thread with the header test locations, meter settings & grounding differences found. We tried (without success) to use grounding straps to improve the header/downpipe/cat grounding properties.



Thanks... You are correct.. mili ohms differences can make the signal so weak that the signal is never read by the ECU.

This Saturday



Like DC Scotty said, just bunch of things, I try to update the first post to the current information though

Just wanted to give an update on what i was doing.
I am almost ready to install the Bosch 4 wire O2, I have been driving for a couple weeks and i got all the CEL's cleared. My MPG went up last tank so i am going to see if it changes again. I also got my alignment fixed so i might wait another 2 tanks before i swap in out. I am noticing some weird things with the idle, and bogging at certain RPM's, so i will notice a difference after the swap.

You need a high current, low ohm meter to see it, or just connect the O2 heater circuit and measure the voltage difference between ground at the battery and the header at any point along its length.

At home I have a Racal-Dana 5004 that measures to 10micro-ohms, but the 7150's at work have trouble measuring .1ohms accurately.

Mike

Great news.. Please keep up posted.. Check your vacuum lines and make sure the EGR solenoid vacuum/electrical connections are good. Im convinced that this solenoid contributes to some of bogging problems by dumping the canister contents inappropriately. Also, make sure the two plugs inside of the solenoid are not bent, causing a weak connection. Testing across the terminals should be 30-40 ohms otherwise replace (my old one was way off @ 2.14 ohms).

I started my testing with the Bosch 4wire O2 and saw positive improvements from 24-25mpg to 29-30mpg range after clearing the ECU Relearn and only 2 tanks. But I changed back to the old O2 sensor when I noticed loud ticking noise from the valve cover (under #1 valve).. Thought it was a failing timing chain tensioner. After opening up the valve cover, we found a pitted cam due to clogged-up oil squirters. Installed a new beefier N1 tensioner and cleaned the squirters. So, Im changing the cams this week and hopefully this is the only damage found (still need to do damage inspection of the lifters & rockers though).. When it rains, it freaking pours... But one saving grace, I have excellent friend on this forum that really helps out with their knowledge, experience, assistance, and spare parts.

Hopefully, I can start testing again later this week..

Scotty, what clogged up the squirters?

It doesn't seem like the O2 sensor had anything to do with it, so are you going to install it back?

No EGR so i dont have to worry about that, I am getting around 32mpg as it sits. I do take it to redline here and there, mostly shifting before 4k and cruising around 3-3.5K. Half interstate/Hwy and half country roads with little city mixed in. I am almost done with this tank and i want to do 1 more after just to make sure my numbers are consistent. Then i will switch over.

My setup if anyone is wondering. SR20DE from a 95 SER in a 95 Sentra, highport cams, GSpec Crank and WP pulleys, JWT flywheel, SSAC Header, Stock SER exhaust, Injen CAI, Outlaw Engineering Thermoblock spacers, CS PS eliminator pulley, Exedy Stage1 Clutch, Nismo AFPR, Nismo Thermostat, Prothane MM, No AC, EGR, rear O2, Cruise, or PS, timing at 19* /w 93 octane, AGX with GC coil overs, ST front and rear sway bars, stock SER wheels, and Full interior minus carpet with minor weight reduction.