Any Ideas what to test next?

[LNL92]

92 4.0L manual 4x4 200,000 miles. One day my check engine light started coming on and off and i started getting horrible gas mileage and motor was running rough (i always use fuel system cleaner at least every 3,000 miles). I changed the fuel filter, didn't get better. Changed plugs and wires and it got a tiny bit better. I cleaned maf sensor, cleaned the throttle body sensor, air temp sensor checked and cleaned, cleaned and checked PcV, put in new o2 sensor (checked and it gets up to 2.o volts and then keeps rising instead of droping and staying in .1 to .9 ranger when warmed up. can't find vacuum leaks, took a can of carb cleaner didn't bog down when sprayed around manifold. checked compression 131, 132, 140, 150, 150, 150 for my six cylinders, took wires off plugs while running each one affected motor the same. new KanN filter, fluids don't have any discoloration. has plenty of power in all gears (except going up hill in 5th gear i'll be going 75 get to the top of hill and it bogs down causing me to shift to 4th. Changed the CAT, codes keep coming up 172 lean and 173 rich. I'm thinking my computer is messed up and won't get out of open loop mode.ANY IDEAS? went from 22 mpg on highway to 16.

 

[adsm08]

Two things.

1) Coil pack.

2) A genuine oxygen sensor should not be able to produce a signal over 1.5V. That means one of two things has happened. Either you tested it wrong, or something sold you a catalyst monitor instead of an oxygen sensor. They look the same, operate similarly, and are used for similar things, but operate in two different voltage ranges. A cat monitor sensor will operate around 2V.

 

[LNL92]

So i checked my ignition coil and getting plenty of spark. It is an 02 sensor that i put in not the catalytic sensor (i got the bosh sensor that is listed as the one, not the universal one) could i have gotten an o2 sensor that is for a different motor but same year? I got it hooked up to my buddy's dads computer scanner all my sensors are running normal except it stays in open loop mode and the 02 sensor doesn't read back an forth rich/lean it just says rich. I have plenty of power but am getting extremely poor fuel mileage because its just dumping in so much fuel. also checked my intake manifold bolts and all torqued to 216 inches of torque (heard sometimes they loosen up and can cause bad fuel mileage). Does anybody have any ideas? Learning as i go that is mechanics i'm starting to think maybe something is wrong with my computer, but like i said i'm learning mechanics as i go.
thanks for any advice/input.

 

[chazzone]

Have you checked the fuel pressure at the rail? Have you checked the plugs? Are they all rich, or is it just one or two? It's possible that one or more of the injectors is/are leaking.

 

[LNL92]

I have checked all the spark plugs and all 6 looked the same. all are burning rich. i have not checked the injectors because i regularly use injector cleaner and while it runs i can't spot any leaks. i will check the injectors though, thanks for the input.

 

[BLOODBANE]

My Explorer kind of did the same thing a little while after I got it. CEL would come on and throw lots of different codes, some fixes seemed to help (new MAF, TPS, O2, etc.), but would always throw a code somewhere. ECM was shot. I opted to put a new one from FORD in, and no more problems, but from what you have done I would try a Junk Yard unit and see if it does anything for you. Keep us posted.

 

[RonD]

The ECT(engine coolant temp) sensor is the "choke" on engines with EFI.
It is a two wire sensor that is usually located next to the 1 wire temp sender for the dash board gauge.

The ECT signal tells the PCM(computer) the engine temp via resistance thru the sensor.
When ECT tells PCM engine is cold the PCM runs injectors rich and advances timing, like a "choke" did on a carb.
If this sensors acts up you can run rich all the time or lean(hard to start when cold), or it can vary between lean and rich.

The ECT can be tested with an ohm meter, as engine heats up, resistance will change.

 

[robertc1024]

+1 on the ECT. Test it. Here's the info: http://oldfuelinjection.com/index.php?p=28

 

[RonD]

Excellent link

 

[LNL92]

Problem solved it was the fuel regulator

 

[RonD]

Thanks for posting the fix