[rcoe]

Did not have any issues with them last year.

This spring in the process of tracking down an issue I replaced both upstream sensors with the cheap ones from Oreilly's.

Since then I will occasionally get an O2 code for one bank or the other and during my track day last month the plug on the drivers side got a little close to the header and the wires going to the sensor got a little melty, but not enough to short out.

So last week got a quality set of sensors, pulled out the extension on the drivers side(does not look like it was needed). Inspected the plugs and wiring going up, installed new sensors with a squirt of dielectric grease on the connection. Wrapped the wiring and plugs in heat shielding. I also pulled the downstream sensors and terminated their plugs.

I fired it up while on the lift and noticed I had very small exhaust leaks on both sides at the header connection clamp, a little exhaust fabric tape under the clamp fixed this.

All should be good except when it is cold 1st 5 minutes or so of driving part throttle is trending very lean lambda hovering at 1.4 or so, if I get on the gas she runs great. Once it gets warmed up runs great, under normal driving I can easily tell as the lambda will be pegged very close to 1 once it is warmed up.

Any ideas on what is going on here or do I just need to let her warm up real good before driving?

[cjperformance]

I would guess it's the exhaust leak not being completely sealed up and air entering the exhaust before the O2.

[rcoe]

Originally Posted by cjperformance

1.4 would be lean. Greater than 1 is lean, less than 1 is rich. That looks like 40% lean... I would guess it's the exhaust leak not being completely sealed up and air entering the exhaust before the O2.

Yes lean because under full throttle it holds very steady at .83.

I have had it running on the hoist and can feel no exhaust coming from the headers, only place was at the clamp after the sensor. Maybe I will check from the topside best I can and check the torque on the header bolts.

And why would it clear up after the car is fully warm?

[cjperformance]

As thing heat up they expand and little gaps might tend to go away.

But I guess the real question is... is it really that lean or just the reading? Do your narrow band o2s agree that things are lean? Or is it even going into closed loop during this period?

What do fuel trims look like on a log?

Sorry, just shooting in the dark. IMO, step 1 verify in some way whether or it really IS or ISN'T running that lean on startup.

[6spdhyperblue]

First things first. Stop all the exhaust leaks

[Nick S]

Originally Posted by rcoe

Did not have any issues with them last year.

This spring in the process of tracking down an issue I replaced both upstream sensors with the cheap ones from Oreilly's.

Since then I will occasionally get an O2 code for one bank or the other and during my track day last month the plug on the drivers side got a little close to the header and the wires going to the sensor got a little melty, but not enough to short out.

So last week got a quality set of sensors, pulled out the extension on the drivers side(does not look like it was needed). Inspected the plugs and wiring going up, installed new sensors with a squirt of dielectric grease on the connection. Wrapped the wiring and plugs in heat shielding. I also pulled the downstream sensors and terminated their plugs.

I fired it up while on the lift and noticed I had very small exhaust leaks on both sides at the header connection clamp, a little exhaust fabric tape under the clamp fixed this.

All should be good except when it is cold 1st 5 minutes or so of driving part throttle is trending very lean lambda hovering at 1.4 or so, if I get on the gas she runs great. Once it gets warmed up runs great, under normal driving I can easily tell as the lambda will be pegged very close to 1 once it is warmed up.

Any ideas on what is going on here or do I just need to let her warm up real good before driving?

Dielectric grease is actually non-conductive. I hope you didn't actually squirt it into the connection terminals. It's really intended to be used more around the outside of the connector to help lubricate the connector when installing the two halves together and help keep water/moisture out. It is not intended to make a better electrical connection or anything.

If you squirt it into the connection terminals or onto the connection pins it very well could cause a worse electrical connection.

When you say you bought quality O2 sensors does that mean you bought OEM sensors? Or some other aftermarket brand? Personally when it comes to sensors like that I have always found it best to stick with OEM.

[rcoe]

Originally Posted by Nick S

Dielectric grease is actually non-conductive. I hope you didn't actually squirt it into the connection terminals. It's really intended to be used more around the outside of the connector to help lubricate the connector when installing the two halves together and help keep water/moisture out. It is not intended to make a better electrical connection or anything.

If you squirt it into the connection terminals or onto the connection pins it very well could cause a worse electrical connection.

When you say you bought quality O2 sensors does that mean you bought OEM sensors? Or some other aftermarket brand? Personally when it comes to sensors like that I have always found it best to stick with OEM.

There might be some grease on the connection, will feel very stupid if this is the problem.

Oem sensors.