Guys got a 99 em1 with a hondata s100 its bogging when it's warming up showing front 02 sensor code low voltage. I tried plugging in the stock si comp and showing the same front sensor code with that one too. I checked the fuses and power and ground both at the sensor and at the plug end of the harness. Everything checked ok there, but looking at the voltage of the 02 sensor with the key on position my sensor read .39-.40vlts. I plugged the sensor back in started it up and held the throttle at 3500rpm's then let my foot off the gas then the sensor started too read. Once the rpm's dropped too normal it read 0. I've never seen a 02 work backwards like this. It's not running rich right now but it's running better with the sensor unplugged in fail safe mode.It's a brand new honda 02 in the car now. Well this be a problem for the motor driving it too a shop for repairs. Is it going to hurt the motor? Any ideas would be appreciated thanks need help fast gotta fix this.

 

All others sensors checked out ok tps map sensor and intake temp and check coolant temp as well even though i'm not getting the codes for them. I checked the via 15amp fuse tonite for that circuit still nothing. I'm at a stand still with this any ideas?

 

Have you measured the fuel pressure? Is the pressure at spec with and without the FPR vacuum hose connected?

 

I have a fuel pressure gauge mounted on top of my fuel filter got it set at 40. The plugs are all black and smell like fuel. I swapped ecus today and ran the car at idle with a oem si comp. I idle the exact same way as with the p28 storing front o2 code still. I'm going to grap an o2 from my buddies si tonite that i know is good, and try putting that one in my car and see what it does. I just have a hard time believing that 2 brand new honda 02 sensor's go bad.

 

Your fuel pressure may be too high. At idle, what are the fuel pressures with versus without the FPR vacuum hose connected:

 

I have the fuel pressure bumped up a little bit above stock at 40. Last night i put my buddies o2 in the car it ran ok but still bogged a little out the tail pipe. At idle the gauge read 40 when i disconnected the hose it went up. I will checked again today and see how much it went up.

 

The O2 sensor code is most likely caused by your fuel pressure being too high.

 

What i don't understand is that once i put the aftermarket 02 sensor in the car it seem too run better with that one. But aren't honda 02's better to use than aftermarket ones. I will do the fuel pressure test.