Wires Clipped on O2 Sensor
 

While I was underneath my 944 trying to loosen the starter mounting bolts, I noticed that the wires to the O2 sensor had been clipped by one of the prior owners. Any idea why someone would do this?

The car seems to idle rough. Idle is steady, but it's rather noisy (though this is my first 944 so I'm not 100% sure what it should sound like). Could this be related?

Could be highly related.

The times I've seen cars run without the O2 sensor hooked up, they really ran ragged at idle. Without the O2 sensor, the DME won't be able to set the air/fuel mixture properly.

I don't remember what the color of the wires are, but it oughta be easy to hook it back up. You really can't run without them.

If it's idling steady at 800rpm. it's ok. The noise may be something else (ie. bad exhaust).

It doesn't need the O2 sensor to run. The fuel mix is primarily set by a lookup table in the DME memory (ROM). The O2 sensor just 'fine tunes' the mix for the optimum air/fuel ratio at the inlet.

Some early ROW cars don't have an O2 sensor.

It may run rich or lean at idle if someone has played with the air bypass screw on the AFM.

Cheers

Without the O2 sensor the car is going to run mega rich. Its basically going to run on preset fuel maps (default rich mixture) as if the car were still in warm up mode. Depending on the year of your car you will have the 3-wire O2 sensor or a 1 wire. The 3-wire is two black and one white wires, the 1-wire im pretty sure is just a black wire. Just splice them back together and you will be fine. The two black wires can be swapped, the white wire is the only imperative one (this is assuming you have a 3-wire).

The A/F O2 correction runs "open loop", without O2 sensor in the circuit, when the DME II temp sensor senses a cold engine. Once warmed-up, the A/F O2 correction runs "closed loop" with O2 sensor in the circuit.

Could be the O2 sensor went bad causing lean issues and it was cheaper to cut the fix.

I know from experience that the car won't pass emmisions without the O2 sensor hooked up.
Jeff

On most non-turbos the O2 sensor is a cheap and quick replacement. No reason not to go out and fix it even if the car runs OK. It will most likely run better afterwards.

That certainly would fit with some of the other "repairs" the previous owner performed on this vehicle.

My 944 is old enough that I don't have to worry about emissions testing. That said, once I take care of the more pressing repairs I'm going to replace it.

The O2 sensor that was in there was a 3-wire, but from what I gather the early 944s originally came with a 1-wire (mine is an 83). I take it that it's possible to hook up a 3-wire O2 sensor to a 1-wire car?

some of the early 944's had a three wire, depending on where they were sold. my '83, for example, was sold originally in california, with california emissions, and had the three wire O2 sensor.

i believe it is possible to hook up a 3-wire to a one wire sensor. the other two wires are to heat the sensor at start up. if you do a search, you will find a part number for a ford O2 sensor that is about $30 and works great. that is what i used on my current 951.

According to CarFax it was originally bought in New Jersey. The only other state it has been registered in is Connecticut. I only saw one wire hanging down in the vicinity, but I didn't do an exhaustive search.

Is there a way to hook up the heater wires so that the advantages of the 3-wire sensor can be had or would a 3-wire sensor in a 1-wire car end up being used as if it were just a 1-wire sensor?

if there is the wiring necessary for the heater wires, you could do this. i'd have to look at the engine bay, etc. others may know more about this.

look at the harness connector to see how many wires it has. usually the white wire is the sensor wire and the other two wires are the heater wires/ground not present on a one-wire system. the harness connector is located at the rear of the cam tower on my late 85 na and is three wire. possibly the number of wires changes mid-85 model year from one to three.

i have read that splicing o2 sensor wires in an unapproved fashion will cause performance problems. the recommendation is you either get the opriginal bosch o2 sensor complete with harness (pricy!) or buy the bosch generic o2 sensor {with the proper number of wires}complete with splice kit at autozone perhaps for around $80.