Stuck in closed loop

[novajoe]

My 86 camaro with a 396 TPI motor is stuck in closed loop operation (limp home mode) I don't have any DTC's (trouble codes) and all sensors are new only thing that looks strange is a .39 (lean) volt reading off my O2 was the same on the old sensor. This reading does not change at all???? The car is running really rich. Any Ideas? I am running out of them.

HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!ConFused

[socalmach]

So the new MAF didn't help?

[Jazz]

Is it possible the wiring to the O2 sensor is bad?

[novajoe]

Checked that the computer knows if I unhook it but it doen't care about the reading. I will try to run a new wire this weekend.

[novajoe]

So the new MAF didn't help?


Yes it helped, but didn't fix everything

[jimbolaya]

Is it possible the wiring to the O2 sensor is bad?

I'm not a real knowledgable car guy, but I was thinking what Jazz said makes sense. If the o2sensor was unplugged, the computer would substitute the preset o2 reading just as it does in closed loop. So maybe there is something wrong in the wiring for the o2. Frayed wire or melted wire skin due to heat. There is one thing that kinda contradicts this theory is that I would think the preset closed loop o2 reading would cause you to be rich not lean. Just something to think about. If that sounds stupid, just ignore me. :wrong:

Jim

[novajoe]

I'm not a real knowledgable car guy, but I was thinking what Jazz said makes sense. If the o2sensor was unplugged, the computer would substitute the preset o2 reading just as it does in closed loop. So maybe there is something wrong in the wiring for the o2. Frayed wire or melted wire skin due to heat. There is one thing that kinda contradicts this theory is that I would think the preset closed loop o2 reading would cause you to be rich not lean. Just something to think about. If that sounds stupid, just ignore me. :wrong:

Jim


No that wasn't dumb. I was thinking the same thing. But after running a new wire from the O2 to the ECM and no change I am guessing that wasn't it. The O2 should read lean if in open loop as a saftey. The lean reading makes the computer richen the mixture to prevent a lean run. But I am still at a loss on why I cant get closed loop operation????:WTF:

[edcmat-l1]

No that wasn't dumb. I was thinking the same thing. But after running a new wire from the O2 to the ECM and no change I am guessing that wasn't it. The O2 should read lean if in open loop as a saftey. The lean reading makes the computer richen the mixture to prevent a lean run. But I am still at a loss on why I cant get closed loop operation????:WTF:

Not really. The 02 is gonna report whatever it sees, once its hot enough to work, regardless of open or closed loop.
The only dif is whether or not the ECM has decided the switching is sufficient, along with the coolant temp, for closed loop operation. Until then, its stays right around 440 mv. As it warms its climbs slowly, based on the added fuel from the open loop table. If the open loop fueling is off, for wahtever reason, the 02 may never climb, and never get to a point where thee computer thinks its ok to go to closed loop.
Do the tests I told you to do, and let me know how that goes.

[novajoe]

Tested it and .93 volts to ground and .44 volts through my hand

[socalmach]

Isn't that what it's supposed to be at?

[novajoe]

Yes it is. But It still wont go into closed mode

[Jazz]

Wonder if maybe you need to try another ECU? Mabye there's a problem in there someplace?

[edcmat-l1]

Tested it and .93 volts to ground and .44 volts through my hand

If you ground the wire, it should go to zero volts. If you hold the end of the wire in your hand (the bare end of the wire, the connector, or an attached jumper wire, but you need to be holding bare wire or the metal pin of the connector) and touch your other hand to the positive terminal of the battery, it should go to approx 1 volt. You are using your body as the resistor.
With the wire disconnected, and just hanging, not touching anything, you should see approx 440-450 millivolts.
You should not see 990 millivolts with it touching to ground.

[novajoe]

I also have a bad relay on the mas burn off I will be replacing the socket as soon as I can get my hands on a new one