It "L-I-V-E-S" the smoking gun??? (pics included)

kilodawg · kilodawg's Garage

Okay sorry to bore you all with this but I went back and carefully looked at the connections to the O2 sensor thinking that when the exhaust "dropped" I might have unplugged something.

The connections down at the sensor itself looked okay I think.

However, then I followed the wires buck up to the top rear of the engine near where the reference sensors are and found that a black wire splits out and heads to this brown thing (technical term

) that is cracked in it's housing.

This would have been the shortest lead when the exhaust "dropped" and would have received the bulk of the stress. It's location probably also suggests that this was the cause of the either the speed or reference sensor coming loose as well. So the part number on the black rubber boot is 477 091 252 but it doesn't come up in the Pelican data base or the PET. However, Pelican does say that people searching for it also search for the O2 sensor.

So where do I go from here experts????

For reference a closeup of the speed and reference sensors with my tape job on the back of the sensor side of the connector that is deteriorating....

962porsche · 03-11-2009, 07:19 PM

what in gods name are you talking about ? are you saying you broke the connector to the o2 sensor ? the black boot is on the o2 sensor and is not part of the connector . so is the car dumping fuel ?running lean ? how is the car running OK ? the broken connector is part of the wire harness .from the looks of it its not pluged in all the way .some times you have to loosen the 13MM nut on the clamp to plug it in all the way .

kilodawg · kilodawg's Garage

Look at where the black boot connects to the tan brown (ceramic?) piece on the right of the picture. That piece has a wire that runs through it and I assume runs down to the O2 sensor through the boot. The brown pice is cracked and broken although the wire still runs through it. Since it's the input to the sensor I assume that is where the problem lies...Unfortuanately I don't know what it is or where to find a replacement....

As I said the car runs great for the first 5 minutes or so (open loop from the O2 sensor?) and then bogs down and runs like crap (closed loop?)

mikepellegrini · mikepellegrini's Garage

I cracked the same O2 sensor connecter on my 83 NA. The wire inside was intact, so I just wrapped it in electrical tape and it's good to go. An easy fix.

962porsche · 03-11-2009, 07:35 PM

i was just looking at your other post why is there two ? the o2 sensor goes to the electric control unit and tells the car how much fuel it needs and when it needs it . the control unit will not get a reading untill the sensor get up to operating temp. i would say thats why the car is running like crap when it starts getting up to temp .

962porsche · 03-11-2009, 07:46 PM

in the day light i will see if i have one for you if i do i will put it in the mail for you no charge . just PM me your address .

kilodawg · kilodawg's Garage

So I checked this morning and my O2 sensor has all three wires going into the sensor on the exhaust. Nothing is loose there.

On the other end the two white wires are secure attached to their corresponding plug per the picture.

The black wire seems to be attached to the central pin inside the black rubber boot although the brown plastic housing itself which is part of the wire harness I now understand is cracked and falling apart.

Since my symptoms seem to be consistent with a bad O2 sensor and it did receive some trauma when the exhaust dropped I am till focusing my attention here. The question I have is whether the sensor at the exhaust broke internally or if the broken brown plastic on the wire harness is the root cause.

It would help if I knew why that brown plastic was there in the first place and what purpose if any it served. If that's a red herring then I would just go and install a new sensor. If not though then the sensor replacement would be money not well spent....

many944s · 03-12-2009, 05:34 AM

There is nothing magic about the connector. It isn't a shielded connection or anything. You can completely remove the broken connector and crimp on a set of spade or bullet connectors and be just fine!

hope it helps!
-Nick

kilodawg · kilodawg's Garage

Very good! If that's the case I guess I'm off to get an O2 sensor.

Mask of Destiny · 03-12-2009, 06:55 AM

Before you go off to buy a new O2 sensor, a quick test is to just disconnect the O2 sensor completely. When the sensor is not connected, the DME will stay in open loop mode. If the car doesn't bog down after a few minutes like it was before, you've confirmed the culprit.

kilodawg · kilodawg's Garage

Okay, disconnected the O2 sensor and went for a spin. The car was just a little off right from the start. Not quite as smooth as yesterday BUT it never bogged down after a good 15 minutes. It always drove consistent.

So a new O2 sensor is on order. Now back to the wire harness connector. I was wondering why it comes in that hard plastic casing on the firewall. Everyone tells me that it's nothing special and that it won't make a difference if it's broken. However, I did find a post that implies it was thermal shielding to isolate the wire from heat sources other than what comes up along the wire from the O2 sensor. Does this sound plausible?

As I have come to the conclusion that my O2 sensor was busted (and it wasn't broken prior to the recent engine work) if that connector isn't the culprit then there were TWO areas of damage to the circuit when the exhaust dropped. One in the sensor itself and one at the wire harness connection on the firewall.

Thought? Next is how to get rid of the belt squeal on start up while I wait for the new O2 sensor to arrive....

JonA · 03-12-2009, 04:04 PM

Tighten the belts (power steering, compressor, alternator). A loose belt is likely to squeal on start-up. The adjustment is underneath, jack up the front end a little to get your head under there.

Jon

kilodawg · kilodawg's Garage

I know the adjustments well since I just finished putting the whole thing back together. I thought they were tight enough but I did clean the pulleys and may not have gotten everything off. I'll check again. However, knowing that the O2 sensor is the problem and that now there are no leaks of any kind is a good feeling...Worse comes to worse I'll trace down the specific belt and replace it if necessary....

kilodawg · kilodawg's Garage

Just to close the loop.

I installed the new O2 sensor this evening and it runs like a champ. Even the belt squeal has gone away. It just needed to be driven a bit until the last of the degreaser remnants came off the pulleys.

So the major front end project is complete. No significant issues just took time and patience. Pictures this weekend.....