Okay: 1989 245 with a check engine light. Codes 113, 213,232
If I'm getting really bad MPG (say 8mpg) is it safe to say that its running rich? And if its running rich can I rule out a vaccuum leak?

Also, I've tested the oxygen sensor output. If I disconnect the single lead and test it, its maxed at about 1.000v (meaning full rich). The other end (the green lead) has a constant .5v (is this a reference voltage?) but oddly if i plug the leads back together I get no voltage!

what is going on?

 

Yes its running rich.

I would:
1. disconnect the vacuum line that goes between the fuel pressure regulator and the intake and look for a gas leak (bad FPR).
2. With everything connected and during idle you get no voltage on the green wire? With the power off disconnect the green wire and measure the ohms to ground on the side of the disconnected wire that runs to the ECU, looking for a short.
3. Code 2-1-3 has to do with the throttle position switch, make sure it clicks when you move it by hand.

Normally the o2 sensor will swing quickly between .2 and .9 VDC during idle.

 

Thanks for the reply Bubba240, I have checked the FPR vaccuum line...all dry. RE: the O2 sensor wire. Unplugged, the green lead has .5v, when measured to ground. Plugged in to the O2 sensor, 0v. To do the test that you're saying should I disconnect the plug from the ECU before I check its resistance?

 

Even though I don't think it would hurt anything, you might disconnect the ECU plug to be safe before measuring the resistance of the green wire to ground.

 

Go buy a new O2 sensor and clean your throttle switch to make sure its not stuck on.

 

Adub-
My last o2 sensor has good numbers, but I still put in a new one. Again, I get readings from the sensor (it starts low but quickly climbs to near 1 volt) when its disconnected from the green ECU wire. Also, when unplugged, the green ECU wire has .5v show. However, when I pplug them together, the voltage drops to zero.
The throttle body is freshly cleaned and the throttle switch clearly clicks when when the throttle is moved.

 

Hmm pull the injector rail get a pan (aim injectors into pan, very important) have someone turn the car over while you look at the spray pattern and the pulse. They should pulse and have nice cone shaaped spray patterns. If they are just constantly on....

 

what is your fuel pressure ? it should be 3 bar ! if that is good and you have the .05 ref voltage from the ecm and the 02 sensor did sweeps check and make sure that one of the dtc's you are getting is not in air mass meter, this will also cause your issue of running rich. also does you 240 have a egr valve ?

 

i would suggest checking:
1 Idle Speed, ignition timing and idle mixture: adjust
2 check your Fuel pressure: test & or replace pressure regulaor