Hi everyone. I'm usually pretty good at figuring out things but this has me stumped. I have Pypes true dual exhaust and I think my O2 sensor isn't getting hot enough. The idle is stay high since the cold weather set in. Question; is there a way to tell if the ECM is in closed or open loop and how can you tell the O2 sensor is hot enough?

 

That might just relate to a story, that I heard from the mechanic at the Shop next door to mine. He was telling me, that his buddy with a C6 had put aftermarket headers on his C6 and had the same problem. The problem was, that the new headers were thicker in the area where the O2 sensor went and it would take a lot longer to heat it up. What he did, was swap the O2 sensors from the rear part of the exhaust system, where it was thinner, because those sensors were designed to come on faster (lower exhaust temp, thinner material) and that fixed his own problem.

Hope this helps.

 

Did you eliminate the catalytic converter? If you did that's why your O2 sensor isn't getting nearly hot enough to go to closed loop operation.

 

Has the physical location of the O2 sensor changed/moved with the Pypes installation?

 

A friend of mine had a car he ran into this problem with, the car wasn't designed with a heated O2. When he installed higher flowing exhaust without cats, cruising down the interstate at 70 for long peroids with his 248 gears the car would set an O2 engine code, due to the O2 being at the end of the LT headers getting cold. The options were install a heated O2 and power circuit to power it or, increase the RPM while driving so he just drove 75-80.

 

The location of the O2 is in the same spot and that's about 3-4feet from the engine. I did remove the catalytic converter so that entire area is running cooler. That's why I suspect it's the O2 sensor not getting hot enough. I still would like to know if I'm in closed or open loop??? Nobody knows how to check? I have the scanner but very limited info and I have no check engine lights. That's another reason why I think it's O2 sensor temp.

 

I was always under the impression open/closed loop was controlled by engine temp. Use the scanner to check the engine temp that the ECM is seeing, if it never gets to operating temps I wold start there.

 

You are correct, the O2 sensor is not getting hot enough, because of the changes you made.

I talked to my buddy and I've got to rework my story, as he corrected me. It was because the headers he installed on the C6 were thinner than the factory cast manifolds and they didn't hold the heat in, like the cast manifolds, so the O2 sensor, never got hot enough to operate.

That's when he switched the front O2 sensors for the rear O2 sensors, because they were designed to operate in a cooler area and with a thinner material (the exhaust pipe, versus the cast manifold) and that cleared it up. The C6 has four O2 sensors in two pairs, front and rear. Obviously, they are different.

Here is a C6 thread discussing, just that:

https://www.corvetteforum.com/forums...longtubes.html

More:

https://www.corvetteforum.com/forums...o2-sensor.html



Here are a pair for sale on Ebay

http://www.ebay.com/itm/2006-Corvett...9WYmBl&vxp=mtr

 

I checked the temp reading and I'm a steady 180-195 on water temp. I did a little checking and you are right about the different O2 sensors but on the new vettes, they are 4 wire hook ups in 2006 . The early 80s had heated O2 sensors but that's gonna take some wiring and knowledge to choose the correct sensor. At least I got a pretty good consensus on the O2 sensor . Now I have to decide to move its location, wire a heated sensor or reinstall a cat. I bought one with my Pypes system but I didn't install it. Just put it on a shelf just incase someone reinstates inspection for classic cars.

 

You're welcome, but the real thanks, should go to Hector and I'll tell him about this. I'll also ask him, what you should do, as he's a pretty amazing wrench. He doesn't have any formal training, but he's been working on cars, since he was 13 years old. He figures out stuff, that nobody else can. I'll let you know tomorrow or later tonight.

 

Just to let you know.....the 'open loop-closed loop' is controlled by the O2 sensor. This is why GM and other manufacturers NOW use heated O2 sensors to take the heat of the exhaust out of the equation. Engine temp is not the controlling factor...because you can be a 200 degrees Fahrenheit and have a car running rich at idle and the computer will not go into closed loop due to the excessive fuel keeping the O2 sensor cool. I have seen them many times go in and out of 'open loop-closed loop'.

For what it is worth....I have installed the heated O2 sensor in cases just like this and it is not that big of a deal. No need to move the bung for the sensor. And I am having a 'brain fart' at this exact moment...but I believe that the one I installed was for a C4 ZR-1 and it was three wire. One wire to a ground...one wire to switched 12 volt power source that is fused ( about 7.5 amps I believe) and the last wire is the wire that you have in your wiring harness currently that goes to your ECM.

Either way...installing a heated O2 sensor is a good thing...regardless if you add the catalytic converter or not.

Just my opinion on this.

DUB

 

Thats good to know.

 

My first thought would be to check the IAC valve. It could be stuck letting excessive air into the throttle body. Also, if that doesn't work have a tuner look at your tune. There are several spark and fuel tables that add/subtract fuel/spark depending on the environment. There is also a table that controls the IAC valve. These need to be looked at when making engine/exhaust modifications.

 

I would expect the system looks for both a minimum coolant temperature and for the 02 sensor to be producing an output before it will attempt to go closed loop. There could be a minimum running time too. Every other GM injection system I've looked at uses coolant temperature to set idle rpm, not open vs closed loop. So I'm surprised that open loop would cause a higher idle. I'm not sure if the crossfire does it differently though. There's not much info or support for the original ECM. You should be able to kick it into closed loop by giving it a hard run to see if it makes a difference.

Almost any 3-wire or 4-wire sensor would work if you wanted to try that.

The 3-wire typically have 2 white wires which are the heater wires. 1 to power and the other to ground. Then, the sensor output is typically black.

The 4-wire is typically the same as above except it has a grey wire which is the sensor ground. That should be connected to the same engine bolt with the injection harness ground wires attached to it. Likely at the intake manifold or back of head.

I believe the above is Bosch colors. There are other wire colors on a different brand I can't recall exactly. But, they all follow this scheme. The lightest colored pair of wires is the heater. The darkest colored wire is the sensor output and the other wire is the sensor ground.

Try mid 90's trucks for a 3-wire sensor or almost any V8 97 or newer for a 4-wire. Some parts sites list enough detail you can tell if they are 3-wire or 4-wire.

 

When I bought my 82, the cat was eliminated and it has true duals with an "H" pipe. The 02 sensor is located on the passenger side exhaust pipe, most likely in the same, or close to the same original location. I have never had a problem in the cold weather since 2012 with a high idle. So could it be possible that your 02 sensor is shot, and a replacement is needed??? I don't think you need to reinstall the cat, but that would be your decision.....

 

Wow, thanks everyone! It looks like a heated O2 sensor might be the way to go but just for general knowledge, how hot does the O2 need to be. I hit it with a laser gauge and I'm getting between 180 and 200 at the sensor bung. I find in traffic or hotrodding around gets everything happy but I don't want to be jumping out of the car and trying to get a temp reading out on the road if I don't have too.

 

It's fairly new with about 10,000 miles on it. It's also a Bosch. I figured it would throw a check light if it was faulty...

 

I seem to remember my '82 shop manual saying it takes 390 degrees F to go to closed loop. If you put the bung into the bottom of the bend in your header pipe that would probably do the trick.

 

I do know in one of my discussion with Gordon Killebrew....he mentioned that GM realized that when the O2 was so far from the engine that GM tried to keep the O2 hot by the stove shielding around the catalytic and insulation that they put around the O2. Which is why they moved the O2's up to the engine on the left bank in the later years....as I was told...if I remember correctly.

I have to agree......even though your heated O2 may show CLOSED LOOP.....IF you still ahve a high idle ....I would be more concerned IF the COOLANT TEMP SENSOR is correct. and what my voltage at the MAP sensor shows on the scanner.

Not knowing anything about the history of your throttle bodies and intake gaskets...and if for some ODD reason this high idle just started....I would have to consider throttle bodies being worn out.

I knwo I might be talking out my backside....but I deal with the Cross-Fire cars quite often and NOT that I am a leading authority on them...I just know what I have encountered and when I get them in with problems....and where I check 'things' immediately and stop when I usually find a problem that will inhibit me making any improvements until the problems I find right away are repaired.

DUB

 

I'll keep that number in mind, thanks!