Running Rich.

[rdarlington]

Okay, new data. I went out and jacked up the car to re-connect that O2 sensor and lo and behold, it was connected the whole time. Fine. I go for a 10 minute drive, come back and hookup my dwell meter. It's right there mid scale and not budging. Hit the switch at the end of the throttle travel and it buzzes louder and the needle swings to the right. Let go, it comes back to mid scale and won't budge.

I turned the idle mix screw almost a 1/4 turn CCW to lean it out a bit (multiple slow steps, checking each time), but at no point did I see that needle move.

Now the oil light comes on when I hit the clutch and let off the gas real fast. The RPMs bounce very low and then back up. A little lower than what I'm used to. I even stalled it on the way into the garage which is unusual for me. Hooked up dwell meter. Nothing budging.

Old video, but it shows the position of the needle that I saw today and how I have it hooked up:

https://www.youtube.com/watch?v=cpNB1eRktzM

Next step, test the lambda computer I guess? Ground and then +1.5 volts on the O2 sensor lead and watch for needle swings?

-Bob

[jamesvnz]

try a new OXYGEN sensor bosch 11032 they are not very much on amazon

its on the left lower engine in from the back left wheel and a black wire runs out it
my d ran better after a new one and was no longer running ritch

[Bitsyncmaster]

With your new data, It does sound like your lambda system is working but you need a new O2 sensor. Then adjust the mixture (it should be bouncing around after warmup).

You may need to adjust your curb idle and idle switch screws to reduce idle hunt after the mixture is correct.

[rdarlington]

Was afraid of that. I will buy the new one vs playing roulette with another from DMCH (yep, the one I have is "new" from last June.).

-Bob

[David T]

Was afraid of that. I will buy the new one vs playing roulette with another from DMCH (yep, the one I have is "new" from last June.).

-Bob

It doesn't matter how new it is, if you are running rich enough to make your eyes tear it is probably contaminated and needs to be replaced.

[rdarlington]

Clearly I'm not cut out for this. New sensor came in yesterday, got it in today without any trouble. I had my idle mix set lean to start with from two days ago. Went out for a 10 minute warmup drive and back to the driveway. Adjust, close hole, watch needle, rinse repeat. Just sitting as if I'm open loop. At some point I was able to get the needle to swing around. It went up, back to the middle, and then down to the left. Okay. Turn a little more to the right (rich) and it does the same. Based on a lower duty cycle I'm assuming it's trying to lean my mix so I turn back to the left. Same. Keep going, plugging and checking every little bit I turn, and then it sits mid scale not moving. I was reving the engine between tests for about 10-15 seconds at a time.

For a while there I thought I was making progress as I saw the needle swinging back and forth as it went up to the top of the scale and then back down to the left and sat. Damn this car. I have no idea if I was on the right track or not. This is the most I've seen that needle do without me pushing the switch by the throttle. I swear this thing is toying with me. Maybe time to sell it and get out of the DeLorean business. It's funny how something so darn simple is so damn frustrating to me.

-Bob

[David T]

Clearly I'm not cut out for this. New sensor came in yesterday, got it in today without any trouble. I had my idle mix set lean to start with from two days ago. Went out for a 10 minute warmup drive and back to the driveway. Adjust, close hole, watch needle, rinse repeat. Just sitting as if I'm open loop. At some point I was able to get the needle to swing around. It went up, back to the middle, and then down to the left. Okay. Turn a little more to the right (rich) and it does the same. Based on a lower duty cycle I'm assuming it's trying to lean my mix so I turn back to the left. Same. Keep going, plugging and checking every little bit I turn, and then it sits mid scale not moving. I was reving the engine between tests for about 10-15 seconds at a time.

For a while there I thought I was making progress as I saw the needle swinging back and forth as it went up to the top of the scale and then back down to the left and sat. Damn this car. I have no idea if I was on the right track or not. This is the most I've seen that needle do without me pushing the switch by the throttle. I swear this thing is toying with me. Maybe time to sell it and get out of the DeLorean business. It's funny how something so darn simple is so damn frustrating to me.

-Bob

The mixture screw is VERY sensitive. a 1/4 turn and you can be WAY off. Maybe the way to go is to start over and set the mixture so it is just cracking open the injectors. Adjust in 1/16 or less increments. Don't try adjusting until the fans have kicked on and go off at least once so you KNOW the motor is fully warmed up.

[rdarlington]

The mixture screw is VERY sensitive. a 1/4 turn and you can be WAY off. Maybe the way to go is to start over and set the mixture so it is just cracking open the injectors. Adjust in 1/16 or less increments. Don't try adjusting until the fans have kicked on and go off at least once so you KNOW the motor is fully warmed up.

Yeah, my adjustments were very small. 1/16th turn at the very most. Really I was going for as tiny a change as humanly possible with my little allen wrench. I was warmed up. Fans kicked on a couple times in that 20 minutes I was out there killing yet another O2 sensor. This was after driving for a bit.

Would a better way to go about this be using some kind of sealing diaphragm over the hole for the adjustment screw? I'm not sure *how* I'd do this, but making the adjustment while air is leaking in, then pulling the wrench so even more air leaks in, then plugging it seems like a pretty crazy way to do it, although I'm sure it works for everyone else but me.

BTW, while I had the hole uncovered, I could see the needle swinging up to compensate for the extra air so I thought I was on the right track but damn this car hates me.

-Bob

[David T]

Yeah, my adjustments were very small. 1/16th turn at the very most. Really I was going for as tiny a change as humanly possible with my little allen wrench. I was warmed up. Fans kicked on a couple times in that 20 minutes I was out there killing yet another O2 sensor. This was after driving for a bit.

Would a better way to go about this be using some kind of sealing diaphragm over the hole for the adjustment screw? I'm not sure *how* I'd do this, but making the adjustment while air is leaking in, then pulling the wrench so even more air leaks in, then plugging it seems like a pretty crazy way to do it, although I'm sure it works for everyone else but me.

BTW, while I had the hole uncovered, I could see the needle swinging up to compensate for the extra air so I thought I was on the right track but damn this car hates me.

-Bob

As the O2 sensor gets old and/or contaminated you will see less and less "swing". You might also have bad/dirty connections on the O2 wire to the Lambda ECU. Try grounding the wire and applying 1.5 volts to it as per D:04:15 to make sure the Lambda system is functioning properly without the O2 sensor. I have had some limited success "cleaning" an O2 sensor by heating it up with an Oxy-Acetalyne torch to burn off the contaminants. Seems to work for a while at least. Something to try before buying another one. It doesn't take much running at too rich to foul them up. Remember, the O2 sensor signal is VERY small. A bad connection is enough to kill the signal.

[Bitsyncmaster]

When I have seen it hard to set and hold a dwell, the problem was a plugged up CAT. There still could be other problems (ECU, bad injector, bad FV, etc). If you were running rich, it's likely your CAT is damaged.