O2 codes at open loop??

The other day I got in the car to leave from work and made it around the block before a Check Engine light came on. It would go out for one or two seconds, then come on. Mostly under acceleration. I pulled into the Autozone because for one of their free diagnostics (dont want to buy a code scanner, and I know how to use a paperclip to pull GM codes, but not Ford codes!)... Well the codes came up as 41 and 91, which I was apprised were Left O2 lean, Right O2 lean. (Voltage low.) Now this surprised me because the car hadn't reached full operating temp yet. It SHOULD have still been running open loop operation.

Two days later, I get in the car to leave again, and after idling for about 10 seconds, Check Engine comes on. I turn the car off, and turn the key to Ign. to reprime the fuel pump. I do this twice, then start the car. It idles fine, with no light. As I go to leave the parking lot, I tip in on the gas and the light comes on. Every time I hit the gas pedal, the light came on. I didn't have time to pull THAT code, but I assume it's the same code since the only other code my car has EVER thrown was an MAF (out of range) code from running air filter-less.

What would cause my computer to try to read from the O2's prematurely...or what would cause it to even try to go into closed loop before it's ready? I thought AT LEAST the CTS had to read something like 140 degrees and both O2's had to be hot enough to send variating signal voltage.

The only things I've done to the car recently are remove the oil filler cap and PCV return line, block the manifold fitting, and run a breather (valve cover baffling removed, allowed oil into the return line)....and my evap system is currently open-ended. There was a pinhole in manifold line there, so I plugged the manifold fitting. I was going to buy more vacuum hose, but the fitting on the sensor that the gases pass through snapped off, so I left it open. Also note, the car was very low on fuel...the needle was right above the empty mark. Could this have anything to do with my problem? I can't imagine any kind of vaporlock induced by running an open-ended and not an actively pulled evap system, since EFI motors run high line pressure.

I checked my fuel pressure after the codes and, of course, I couldn't get the Check Engine light to come on again. Pressure read 42 at idle, and MOST of the time when I revved the motor, it would spike up to around 48 or so. Although sometimes the pressure would DIP instead, down to about 39. New injectors, AFPR installed.

Sorry the post is so long, but there's a LOT of details I wanted to include. Any help is appreciated. My motorcycle just got hit so it's in a repair shop right now, and I can't afford to have my only other vehicle break down!
 
The computer pulls its engine temp information from the ECT. It is located in the heater supply tubing on the RH front of the engine. The temp gauge may easily be off by 15-20 degrees .

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html
 
Thanks for the links!!

Ok....well let's assume for a second first that the check engine lights that are being thrown are ACTIVE codes, and not the computer throwing some kind of stored code as was suggested to me on another site. Mine has never given a light for a stored code.

Now for the light to come on when the engine WAS ice cold...since it had no way of getting up to operating temperature when it had not been run in 9 hours and was only run for about 30 seconds. I don't know of any engine that can do that...

So assuming all this information is correct....what do you think could cause the computer to try to run closed loop and read from the O2's before a normal operating temp has been reached?
 
OrLackThereof said:
So assuming all this information is correct....what do you think could cause the computer to try to run closed loop and read from the O2's before a normal operating temp has been reached?

Bad ECT sensor - the ECT may tell the computer that the engine is warm enough for Closed loop operation. Here's the table to help troubleshoot ECT problems.

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms