Recalibration needed for O2 sensors? No power, lean, misfire

[drdu]

Fuel pressure regulator 97 Explorer 4.0 SOHC


Lean code along with 4,5,& 6 cylinder misfiring diagnosed. Timing tensioner was replaced first. Replaced #5 fuel injector. No power accelerating. Cat converter was making noises and replaced both cats along with four O2 sensors. Still running lean with no power. Now the new cats are glowing underneath in the exhaust due to lean mixture. Replaced muffler since it also may have been clogged. Still running lean and misfiring. Replaced coil pack. Still lean and no power.

Now it looks like there might be fuel pressure problems which could be the problem. The idle is a little rough but when a load is used when running, the engine is rough with misfire and no power. I'm down to a bad fuel pressure reg or MAF sensor. If the fuel pressure is being blocked by some source, then starting with the fuel filter or maybe the fuel tank pump or screen is clogged for some reason. Limiting the costly reg last means a $500 plus part since it has a braided fuel line attached to it. What else could be the problem ?

Ford tech says the Bosch O2 sensors may have to be calibrated with the PCM. If no code is availiable, then Ford OE sensors will have to be used. And the new aftermarket CATS will have to be calibrated as well.

 

[Papa]

Check for a vacume leak and or bad PCV.

 

[mrboyle]

I have never heard of "calibrating" O2 sensors (we need a smilie of a guy shoveling crap). The first thing i would check is the air filter and MAF sensor. If they are fine the next thing I'd check for is a vacuum leak. If that checks out, then I'd test the fuel pressure.

 

[ExplorerDMB]

an oxygen sensor is an oxygen sensor really. There's no "calibration" in a oxygen sensor. The computer sends a ref. voltage, and power, which is then grounded (and it may send a heater voltage, but thats on certain 4 wire sensors). Anyhow, little lesson on Bosch - everything you buy is really Bosch stuff -- Ford's Injectors and such are really Bosch injectors, just have Motorcraft on it. Anyhow, no - there is no calibration for oxygen sensors. You have an issue else where.

This is how they graph:

http://www.explorerforum.com/forums/showthread.php?t=155495

-Drew

 

[exploded99]

Check fuel pressure at the fuel rail. If its good, then all those parts you mentioned are working ok, and your injectors are getting fed like they should be. A new fuel filter is a smart idea given your symptoms, and it's cheap to do.

Check your throttle position sensor. It should read 1 volt at idle, and sweep smoothly up to 5 volts at full throttle. The pcm uses the tps reading to determine the amount of fuel the engine needs based on how far the throttle is opened (among other things, of course.) If it's bad the truck won't run right.

Test first, then replace parts!

 

[ExplorerDMB]

Please do not double post - I've merged your two threads together

-Drew

 

[Glacier991]

DMB beat me to it. He is exactly correct.