89 245, LH 2.4, Auto, 140k

Symptoms: I posted recently that I installed a new O2 sensor (Bosch 13034) and that I noticed this VERY sharp drop in gas mileage per tank. From almost 300 to barely 150. I put in 7 gallons on Saturday and have got about 70 miles and I'm about out again. The tailpipe is suddenly blowing pretty black, has collected a ton of carbon deposits and had been nice and clean before this. The RPMs seem to fluctuate only slightly, but the engine is running very rough. It seems to cruise ok and accelerate fairly normaly, but is SUCKING gas.

Here's what I've done so far:
First off- I am not leaking gas anywhere, both fuel pumps work, I have not had gas siphoned.
1)Like a jacka$$, I threw away the old sensor after putting in the new. Enough said.
2)While the car is running, I've unplugged the new sensor black lead and double whites and there seems to be no noticeable difference at all in the engine running.
3)I have unplugged each fuel injector one at a time and have noticed a harsh engine running condition with each.
4)Diagnostic Control Function 1: I pulled the codes
1-1-3 "Fault in fuel injectors,"
2-2-1 "Fuel system compensating for extremely rich or extremely lean air/fuel
mixture at cruise
2-3-1 "Fuel system compensating for rich or lean air/fuel mixture at cruise"
5)The "Check Engine" light has never gone on, but it never has and is probably a bulb burnt out.
6) Diag. Control Function #2: everything seemed to check out fine.
7) Diag. Conrol Fucntion #3: The system cycled through the air control valve successfully, then the injectors, 3 TIMES each. Valve-inject-Valve-inject-valve-inject.
To me, it felt like all 4 injectors were pulsing and clicking simultaneously.

I'm not handy with a volt/ohmeter. I do have a multimeter that measures ac/dc voltage, resistance and dc amperage.

Where/what should I look at next?
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89 245 'loaded' with a Great Pyrenees; 91 245 project

After changing a sensor I believe you must reset the computer(s)if you haven't already. Pull the battery lead or fuses and drive for 5-10 minutes. Hope this works. Can't imagine getting that bad economy.

I'm sure everyone would love to know what kind of mileage you're actually getting - with your method, for all we know your float/fuel level sender is broken.

1. Fill the tank to the top.
2. Reset trip odometer
3. Drive
4. When the fuel gauge reaches red, fill the tank to the top again.

The amount you replace should be very close to the amount you burned whilst driving. That amount divided by the miles you traveled will give you your actual mileage.

If it were me, I'd try driving around for a while with the O2 sensor disconnected. Even in "limp home mode," I think the car should be getting better than 10mpg. If your mileage is identical or better, that tells you your O2 sensor is bad.

Did you do ANYTHING else to the car while changing that sensor?
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'93 244: 'A' cam 4 deg. advanced, 25/22 sways, custom heim endlinks, fully converted to poly bushings, HD springs front, wagon springs rear.

I did nothing else to the car other than the sensor.

Yep, filled it to the top. $53 bucks. Odo read 651. Ran it till it got BELOW the very bottom white line on the fuel gauge. Filled it up with 14.2 gallons. Odo read 812.
I got 161 miles to that 14 gallon tank.

Then I did the ~7 gallons in. And it's just about below the bottom white line (below the orange) and so far i've driven a little over 70 miles.

I'm dyin' here Scoron!
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89 245 'loaded' with a Great Pyrenees; 91 245 project

I had that 1-1-3, 2-2-1 combination when my former '92 245 was intermittently running very badly. I discovered that my nearly new Bosch 02 sensor was outputting 1.4V on the 02 sensor line. The theory was that there was voltage leaking over from the heater circuit side. Bosch quality isn't what it used to be.

Set your voltohm meter to VDC, 20V scale or thereabouts and measure the sensor output. You should see it swing from about 0.15-0.85V if it is working properly.

Measure your output and see what it is showing. This could just as easily be a problem with the fuel pressure regulator (check for fuel in the vacuum line) or a bad coolant temp sensor telling the computer that it is -40F outside.

Good luck!

Per your and Bentley's instructions:

Ignition off. Voltmeter set to 20 DCV. Pos (red) lead of meter to the black, single wire connector/plug for the sensor in the engine bay. Black lead of meter to ground.
Started car, ran around to meter. Saw the tail end of a "spike?" where the meter read 0.02 then 0.01, then 0.00
I let the car run for 5 minutes and the 0.00's never went away...

Retested it, using battery negative as ground. This time it stayed on 0.02. Then I disconnected the black wire coming from the sensor, from the green wire that runs to the car's computer and put my positive lead on the green wire. It indicated 0.52 on the voltmeter. Car running.


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89 245 'loaded' with a Great Pyrenees; 91 245 project