o2 sensor -broken connector

[ChattanoogaJSB]

Hello all- first time posting here on Pelican after reading some old threads.

A good friend just purchased an 84 911, stock except a Dansk 92.201 muffler showing ~129k with a top end rebuild about 15k miles ago and lots of maintenance records. We drove it 5-odd hours home and it performed flawlessly. This included stable idles at several swaps in driving duties.

A few days later he send me a video of it with a hunting idle only after it's fully warm (20 minutes plus driving). I test drove from cold and experienced the same-

Idle hunts from 750 to 1050 rpm or so warm. Drives fine, smells rich at idle. I cleaned the idle control valve after reading about it because it was simple. No change.

Looking at the o2 sensor - the connector at the boot just below the two white heater wires is broken "almost completely" on the side that looks non-replaceable (the part of the main harness not the sensor black wire. Photos attached.

The damage is baffling to me, in itself, but should I be ohm testing this bare connection? To repair the harness can I solder and heat shrink it? I have read this isn't allowed downstream by the sensor itself because it relies on the air gap but I reasoned it was ok here as it is normally sealed from the elements.

If anyone has insight into this I'm all ears. I've restored 60's Corvettes for years and dabbled in many other cars (and just hauled home a 914 project) so I'm teachable but not initiated into the 911 or the Bosch system. Thank you in advance!

[ChattanoogaJSB]

Photo-

[Nick Triesch]

I just had this happen to me but my connector broke all the way. The wire was severed. It was toast. But you still have the wire connected! I would carefully super glue the connector if you can. I had to have a custom made connector made from a guy on this site! I’ll try to find his name and post it here.

[Nick Triesch]

goth is the guy who made a great connector! Look him up and send him a PM. He can help you.

[ChattanoogaJSB]

Originally Posted by Nick Triesch

goth is the guy who made a great connector! Look him up and send him a PM. He can help you.

Hi Nick! I will look up Goth after trying the glue. Thank you! I may have some corrosion in there and if I do it's no bueno for the resistance that's so important.

In the interim I also found this thread where Louie85 has fairly recently offered them.

(Posted for posterity since there's quite a bit of debate about what kind of connection is best)

http://forums.pelicanparts.com/porsche-911-technical-forum/497025-o2-sensor-connector-3.html

[dfink]

There have been some long an protracted threads about this connector. As you notice it is quite a complex connector to simply attach a couple of wires.
The reason was finally determined to be that the reference air is actually obtained through the wire casing hence the reason for the air tight connection.
I am glad to see that someone is making a replacement connector.
I am not sure however that is going to solve your hunting issue if the wires are still connected.
One of the big causes in the past was the idle switch. Mine has all been customized now but if I remember right there was some sort of plastic piece on the arm that contacts the idle switch. With the car off and your head in the engine bay you should be able to hear the idle switch click as you move the throttle from idle to off idle. If you do not hear the click the lever is probably not pushing the switch and so you are never entering idle mode. I think I had to put a piece of plastic tube on the arm so it would reach then do a bit of tweaking to the arm to get it just right.

[ChattanoogaJSB]

Dfink- fascinating. Is the idle switch issue temperature-related? I'll definitely do the engine-off listen.

As far as the o2 sensor connector I had the thought that it could be bad to have the sending wire exposed to air where it previously was carefully insulated AND also that it might be possible the wire is touching the shielding layer and grounding it out.

It would seem like I could unplug it completely and many threads suggest it will run better open-loop with the dme using the air flow in to achieve a "better" constant (at least roughly steady) stochiometric idle mixture. Like a euro car.

[Elombard]

I think another option is to have a custom Chip made that eliminates the O2 sensor input. I think its an issue in smog test areas though.

I wonder, my carrera has similar miles and I found several old cracked rubber hoses causing small vacuum leaks during recent engine out. I have not fired it up to determine if the slight hunt is gone...I barely noticed it because I have headers and a loud muffler.

I recommend for a fun Saturday....pull out the airbox/afm and the heater blower and gently squeeze and bend all of the vacuum and crank case vent lines and look for cracks and leaks. use a mirror to check all the connections on the back of the Throttle body. They fall apart after 30 years of heat and oil.

[ChattanoogaJSB]

Thanks for the replies guys. I put an alligator clip on the wire at the broken section and actually got good values for the o2 sensor- oscillations between .10 and .80 volts give or take a few hundreds. This is with it warm and whether or not it was hunting idle. Despite the trauma on the connector that seems good. o2 sensor is a Bosch 13003 with about 16k miles and 8 years on it.

The throttle switch makes the lightly audible "click" immediately on and off throttle.

Significantly- unplugging the o2 sensor did NOT cure the hunting warm idle as confirmed by my test drive - nor surprising since the sensor seems to be giving good signal to the connection.

It's not acting like a vacuum leak in that it is completely smooth cold and even after 10 minutes of driving- the idle will drop to around 500 rpm but super stable after a few minutes driving and before it is truly warm.

It idled so well and didn't hunt on our drive home which was lots of 3k rpm cruising which makes me think the service records where they mention upping the mixture are just making a super rich idle mixture that's loading up the engine- nothing the DEM can do to overcome it. Possibility? Need to learn how to adjust mixture as you guys reference. A friend had his 86 mixture turned way up by a prior owner to cover a multitude of sins.

Thanks for those following along!

Benton

[ChattanoogaJSB]

Just an update for all the folks who have been helpful here- I will try and add to the record in case this should turn up in a search and help others-

Received the car from my friend, went through the sections on iac, motronic overview and idle sensor.

Iac valve tested good at 44/22 ish ohms across the pins as described. 12V at central air valve pin. Removed upper duct into iav and used phone for photo on flash- set valve both directions from center and turned ignition on- valve did center.

Valve therefore seemed to be ok with good power.

Warmed up car with o2 sensor (believed good at this time) disconnected. Cold idle perfect as before- warm idle hunted slightly.

Connected O2 sensor- same result.

Jumpered b/c on test port- rock solid idle!

Began to suspect idle valve sticking (working but not smoothly in its full range). Removed and heavily cleaned valve, got a much better "rattle" out of it. Reinstalled, and so far just a hint of hunting but generally much better than ever.

I am suspecting that the idle valve may stick a little until replaced no matter how I clean it. Calling the problem solved pending the replacement.

Also have read that the correct fluctuations of the 02 sensor are .10-.90 volts one or two times a second which I roughly have, but it is possible this is even a little lazy. Newer Bosch unit. I don't have a frequency type analyzer.

Part of me wonders if the air valve is a little sticky and the o2 sensor is even a tad bit slow to report, the warm jumpy idle would be hard to eliminate 100%.

Thank you for all the help for a first-timer!

[ChattanoogaJSB]

Update- idle hunting. Improves to perfection as soon as I remove oil cap. Topic has strayed far from my original premise, beginning new thread.