Mongo

I'm pretty sure the LH is not faulty as it's new. When I check for voltage going to the O2 sensor, do I take my volt meter to the LH side plug going to the O2 (with the sensor disconnected of course)?

dr bob

Andy--

Measurement is with the sensor connected. The LH should be correcting the mixture continuously while the engine is running in closed-loop mode, so if all is well you'll see 0.5 to 0.6 volts on your meter. If the sensor is faulty, or you have an air leak bigger than what the LH can compensate for, you'll likely see a low voltage at the sensor. No voltage is a failed sensor. If the mixture is super rich from a leaking injector or a failed/leaking FPR or damper, the voltage will be high. In normal control mode, you'll see the voltage cycling slightly, while one of the failure modes the volatge will be steady either high or low.

Mongo

Gonna give the test a try this weekend. I have my fingers crossed that this car will finally be back to normal again.

RevAgent

Us too! Let us know how everything goes...

-Mark

Mongo

Okay not to sound stupid, but exactly how do you test it when the O2 sensor is plugged into the LH harness. I mean in the sense of where to connect my voltmeter....

This is one test I have not done, nor ever done in my lifetime.

dr bob

Hate to say how easy it was to add the little test stub to the soldered connection when I did mine last.

It may be that my next 'fix' for the sensor is a 3-pin Molex instead of the soldered and shrink-tubed splice. Crimped pins on the sensor side, and the ability to put a meter probe down the backs of the connectors. I kinda hate to disturb things when they are working so well. Andy, the baby Molex pieces are cheap at Fry's, common at Radio Shack. Get a few pairs. Using the Molex means you can extract the pins to pass them through the grommet in the tunnel, BTW.

Z--
Can we safely speculate the reference air passes through only the signal wire insulation? The current for the heater high enough that I might rather have the for-sure good soldered connections? Thanks for the reference piece too. I do sometimes use the Bosch sensors for coarse/initial tuning on some of the big turbines. They are cheap enough that I don't cry when they get fouled on first-starts of a new engine that has oil residue in the combustor cans or on the turbine blades. I need to add Molex connectors to those too I guess.

John Speake

If you are using crimps it should be possible to slip a thin wires into them to connect to your meter ?

Mongo

I will crimp it up as soon as it stops raining this weekend. I will have a more secure feeling knowing that I"m not using the black harness adapter that came in the box with the O2.

On a side note do they make pills for impulse buying parts?

Z

I really don't know if the signal wire is the only one that the reference air passes through or not. I've never seen any documentation that specifies, and none of the drawings that I've seen really gave a definite answer either.

The Molex connectors seem like a good alternative to the connectors that come with some of the generic O2 sensors. If someone were to solder, and stripped back the insulation far enough to make sure that liquid solder didn't get all the way back and under the insulation, and fresh air could still get in there and between the individual strands of wire, I'd guess it should work okay. I can understand wanting to solder and make sure that there's a good connection, but if you think about it, the other end of the wires at the fuse panel or ECU are crimped there anyway, and so are the wires in the plug of an OEM or Porsche replacement sensor.

Back probing one of the stock plugs might be an option, but for quick and easy checking of the O2 sensor voltage with the engine running, I have about a 6" long harness that I made. It has a stock type 3-pin male plug on one end, and a stock type 3-pin female plug on the other. I can just unplug a car's O2 sensor from the factory harness, and plug the short piece that I made in between. It only takes a few seconds to plug that test harness into a 928 and then the signal voltage can be measured or logged there. The alligator clip connection that you can see allows for quick and easy connecting and disconnecting of the O2 sensor signal from the ECU, allowing for switching between open loop and closed loop operation while still being able to measure or log the sensor signal voltage. I suppose I could put a switch in there instead of clipping and unclipping the alligator clip, but it works well as is, and you can tell at a glance if it's connected or not. With a switch it might require a closer look to tell.

Mongo

Alright, I'm all crimped up and tight here. I found that my black wire had some really goofed up copper strands when I cut the universal harness off, stripped and re-crimped better sections of the wire together. The wires screw-crimped into the universal harness had copper strand sticking out. Obviously signs that there may be continuity and current issues to the LH from that universal harness.

Did it solve my problem? I don't know and won't until tomorrow when I take it for a drive. Wish me luck! I really hope I'm as lucky as Daniel D was in his thread I just bumped. Say your prayers and light a candle in your shark shrines guys.

Mongo

Update: Still having issues.

RevAgent

You're not the only one....took mine out for a drive today; the miss that I thought I had fixed is back...I feel your pain...best of luck...

-Mark

Mongo

WHAT THE F**K???

Just took out and gave it an Italian Tune-Up. Temperature is at 3/4 and it's idling at 675 and still is in the driveway! No idle issues! Did my LH just 'learn' the car?


On a side note, my odometer broke. Apparently there is a Porsche part number label jammed between the tens and units digit of the top odometer. I hope it's a jam as I JUST REPLACED the odometer gears.

jcorenman

Did you re-do the O2 sensor connections? Did you disconnect the battery?

If yes, and no, then maybe the LH had to "un-learn" what it had learned from the messed-up O2 sensor. Disconnecting the battery when you make changes will reset the LH adaptation and let it start fresh.

Hope it continues to behave!

Cheers, Jim

Mongo

I did disconnect before re-crimping the O2. I guess it had to be driven a little longer to adapt to it. I guess John Speake is right about the fact that sometimes they have difficulty learning every now and then, need a tool, or just some time to adapt the idle.