Location: Northern NJ
Posts: 8,576
My VIN: 10757 1st place Concourse 1998
If he is getting dwell readings the Lambda ECU is getting power and it is working, it just isn't in closed loop. There are tests you can do (grounding the O2 lead or putting 1.5 DC volts on it) to make sure the Lambda ECU is working. Once you prove out the ECU then the O2 sensor is probably bad or the mixture screw is WAY out of adjustment. Refer to D:04:15 for the specific tests. Also read the system notes on the previous page.
David Teitelbaum
Location: Houston
Posts: 706
My VIN: 16113
Club(s): (SCDC) (DCUK)
This has me puzzled. I replaced the fuel injectors and the engine is running better. When I start the engine, it hunts fr about three minutes and then it settles down and idles fairly decently. Occasionally it will suddenly start hunting again briefly and settle down. After it warmed up and the fans came on and off several times, I put a dwell meter on it to check it. It consistently stays between 10-11. The other day it seemed to be fluctuating in the 30-50 range so I don't know what has happened.
https://youtu.be/8Ca4UV654cE
What's going on? Bad O2 sensor?
Shannon
Location: Leonardtown, MD
Posts: 9,003
My VIN: 03572
Did you readjust the mixture when you installed the new injectors?
Location: Houston
Posts: 706
My VIN: 16113
Club(s): (SCDC) (DCUK)
Yes, I've tried to but I've had to do it by ear since I can't seem to get the reading off the meter.Originally Posted by Bitsyncmaster
I actually drove the car yesterday down to the street and back. It actually drove well. But I know that the tune is not dialed in. I plan to start the car this morning o see if it still hunts when cold but my bet is that it still does.
Shannon
Location: Leonardtown, MD
Posts: 9,003
My VIN: 03572
If you make adjustments to the mixture for best idle (by ear) it will cause other more important problems.
Location: Houston
Posts: 706
My VIN: 16113
Club(s): (SCDC) (DCUK)
Yes, I've adjusted it so that it doesn't hunt when warm. Did yo use my video? I'm trying to figure out why the meter reading is between and not in the 30-50 range.
Shannon
Location: Rochester, NY
Posts: 2,405
My VIN: 01049
Is it set to 4 cylinder mode?
-Mike
My engine twists my frame.
1981 DeLorean, Carb LS4 swap completed
1999 Corvette, cam/headers/intake manifold, 400 rwhp
2005 Elise, stock
2016 Chevy Cruze
Posts: 4,807
My VIN: 3937
Hey Shannon, when I was doing some dwell meter/mixture setting troubleshooting and fine tuning, it did the same thing where it stayed at one reading instead of fluctuating and also tended to settle in after running for a few minutes. In my case, it turned out to be a bad O2 sensor.
I didn't manage to get my own O2 sensor out and replaced, so I took it to a shop I've used in the past and he got it out, replaced it and then set the dwell properly. Idle and fuel mileage has been good ever since.
I'm sure there is a more technical or scientific explanation as to what happens with that circuit when the O2 sensor fails to cause it to stay steady or not fluctuate or whatever. I don't have that explanation, but also figured I didn't need it after a new O2 sensor in my car fixed it all up anyway.
I couldn't get your youtube video to play by the way. It was marked as private.
Sept. 81, auto, black interior
Location: Leonardtown, MD
Posts: 9,003
My VIN: 03572
If the mixture is to far off, the dwell will read solid low about 10 deg. or high about 85 deg.
Location: Fresno, CA.
Posts: 1,382
My VIN: 16409
When my oxygen sensor went bad I had a pronounced hunting. Oscillation of the dwell meter needle is normal. Remember the lambda computer tries to maintain the correct dwell. If the mixture is set mecanically too lean, the computer attempts to richen the mixture and vice versa. If the mechanical adjustment is too far out of whack, the computer defaults to like a 40 to 50 percent duty cycle.
Chris Miles
For Better or Worse I own a DeLorean!
1983 Grey Manual, VIN #16409, Fresno, California
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Dave M vin 03572
