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Discussion Starter · #1 ·
Hey all,

Before anyone gets worked-up, I have spent several hours trying to find threads on O2 voltage and still don't have a clear picture... I also went to fordfuelinjection.com and think I am a little closer but still need help.

The info I did find was great but I must have more! :thumbup

I have a '90 5.0L 302 EBE.

I am getting code 33.

I have a new heated O2 sensor and a new fuel pressure regulator.

I am slowly but surely checking of my list of things to trouble shoot... I got the list from fordfuelinjection.com... and have two questions I can not find the answer for:

1. I checked the voltage going to the O2 sensor from the vehicle to see if the vehicle wiring is messed-up and frying my O2 sensor. The female harness comming from the vehicle has four receptors that read (starting from top left and going counterclockwise):

- dead... assuming it's the ground
- 12v
- 4v
- 3.5v

The component testing checklist from autozone indicates there should only be a charge of about .45v NOT 4v on the last two receptors.

Is this accurate?

I looked at fordfuelinjection.com and see that the EEC operates most sensors at 5v which makes me think the charge comming from the car is okay.

Does anyone know?

2. The second question is in the Chilton's manual under Heated Oxygen Sensor on page 4-17... the manual says to refer to a table to get the appropriate voltage readings for a connected O2 sensor... but I can't find the table :banghead ... that's why I'm using the Autozone o2 testing checklist... Does anyone know where I can find this table in the book or online? Does the Haynes manual have the table in it?

Thanks for the help! :D

Mike Todd
 

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Discussion Starter · #2 ·
ooops I meant 41 not 33

ooops I meant 41 not 33

It's the lean HEGO or no HEGO

Thanks,
Mike
 

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I can't help you on the voltage, but I'll ask around. In the meantime you can check your fuel pressure and the other things on the list that are free to check.

Did you test the resistance on the O2?
 

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There is only 1 good way to test 02s, and thats with a graphing multimeter....

Good luck :)
 

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Discussion Starter · #6 ·
Yeah, I tested the O2 resistance across the heat circuit... usually the two white wires... 1 ohm at running temp.

Chilton's says it should be 6 ohms at 68 degrees F... uh, it's not going to be 68 degrees outside for months... well I don't have a garage, I could get my sorry bum out there at night and do it then.

Autozone checklist shows the sensor should be between 5 and 25 ohms (didn't say at what temp) but I don't know how much faith I have in their evaluation checklist... not that I have anything against Autozone... they're friendly and helpful at this location.

By Autozones standards, the O2 sensor is shot and the wiring is bad on the truck... but again I'm not sure how much faith I have in thier list.

Thanks
 

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you need to be able to hook onto the output ( black wire ) with a graphing multimeter and watch what the senor is sending to the PCM... it should happily switch between 0 and 1 V.

If the code is saying its lean or not working, this is the best way to test it... this way you can watch if its running lean bias, or if its not working all together..

A system lean code could VERY possibly be a Vacuum leak too....
 

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Discussion Starter · #8 ·
Hey thanks!

One problem... what the heck is a graphing multimeter?.. does it actually print a graph?

Could I just use my multimeter and watch the needle?

Also,

I routed my vac lines according to the diagram... 99% sure they are right.

Visual inspection... no cracks or melting.

Anything else you think I should do as far as vacuum is concerned?

Thanks!
 

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Discussion Starter · #10 ·
Okay, I tested the o2 sensor on the output (black) wire and it fluctuated between .75v and 1.25v... when I increased the gas flow the needle stayed steady at a higher voltage... what a dip :doh0715: ... I didn't write it down... it was steady somewhere between 1.25v and 2v

Rechecked vacuum lines... everything looks good.

It idles like hud and sometimes takes a few tries to start it and keep it going but goes down the road just fine.

Could it be injectors?
 

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Satyr of the Midwest
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Well, starting and idling has almost nothing to do with the HEGO. The only sensors the EEC is looking for information to determine pulse width from (at cold start) are the TPS, MAP, and engine coolant temp (ECT) sensors. Test each of those, and go from there. If it's just having a crappy time while it's cold, I'd suggest starting with the ECT. You should be able to find a graph of temperature vs. resistance/voltage on either the Ford service CD or mebbe on Steve83's supermotors.org page. The other sensors are just as easy.
 

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Discussion Starter · #12 ·
MAP tester?

Will do, thanks!:thumbup

According to the Chilton's manual I need a MAP tester to test the MAP. Is there a way to do it without the tester?

Thanks
 

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Satyr of the Midwest
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Yes, the easiest way is with a 6V lantern battery, some alligator-clip test leads, and either a DVOM with a built-in tachometer or a test tachometer (you can find these fairly cheap at Sears or garage sales). The MAP output is a variable frequency, much like old GM MAF sensors. This is why you can't use an ordinary DVOM to measure output voltage. The output frequency should change proportionally with change in pressure at its port, i.e. applied vacuum with a vacuum pump.

If you go to AutoZone, ask them to print out a test procedure for the MAP sensor. If they have a problem locating that (some employees are idiots), tell 'em to look up a MAP sensor for your truck, then press F9, scroll down to component testing, and it should pop up the part number for the MAP sensor. He should then be able to print it out. It's free, and will even give you a chart for the output frequencies.
 

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Discussion Starter · #14 ·
Thanks!

Okay I tested the TPS and have some results but not sure what they mean.

The Chilton's manual suggests testing resitance across the SIG RTN and the TP wires and the meter read 900 ohms. The table for the test isn't in the manual though... am I an idiot or are the tables really not there.

I see a table on page 4-21 but that doesn't say anything about ohms... only voltage.

Okay, so I measured the voltage according to fordfuelinjection.com and that returned:

5v on VREF
.8v on TPS at idle and the voltage increased as the throttle increased.

Is this what it is supposed to do? It looks as though this is correct according to fordfuelinjection website.

Does anyone know what the Ohms should be?

Thanks!
 

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Satyr of the Midwest
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Don't worry about the resistance. The voltage is easier to interpret. If it started out in the closed position around 0.8 to 0.9V, and steadily increased as you opened the throttle to around 4.4V at WOT, it's fine.
 

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Discussion Starter · #17 ·
Okay,

I've checked the ECT.

About 24,000 ohms and 1.8v at engine cool to touch... cooled overnight.

About 5,000 ohms and .9v at 100 deg F ( I measured the temp at the radiator so the temp at the ECT may have been a bit higher).

About 2,500 ohms and .45v at normal op temp (ran the engine for at least 2 min at 2,000 RPM... I think that's norm op temp... the temp gauge read normal).

It seems as though it is working. What do you think?

I forgot to mention something about the CEL... it comes on after I've been driving for about 10 minutes and as I start driving more slowly (pulling in the parking lot or off the highway) or stop... then the light comes on and stays on until I turn the engine off... it is always code 41 HEGO lean. It does not come on right away.

Does that mean anything?

Thanks for the help!
 

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Discussion Starter · #18 ·
autozone troubleshooting

I went and got the troubleshooting checklist for code 41 and for a MAP sensor from autozone... does anyone know if these things are any good?
 

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Discussion Starter · #19 ·
Does this sound like it is working?

mdtodd said:
Okay, I tested the o2 sensor on the output (black) wire and it fluctuated between .75v and 1.25v... when I increased the gas flow the needle stayed steady at a higher voltage... what a dip :doh0715: ... I didn't write it down... it was steady somewhere between 1.25v and 2v

Rechecked vacuum lines... everything looks good.

It idles like hud and sometimes takes a few tries to start it and keep it going but goes down the road just fine.

Could it be injectors?
Do you think this O2 sensor is good?
 

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Discussion Starter · #20 ·
mdtodd said:
Yeah, I tested the O2 resistance across the heat circuit... usually the two white wires... 1 ohm at running temp.

Chilton's says it should be 6 ohms at 68 degrees F... uh, it's not going to be 68 degrees outside for months... well I don't have a garage, I could get my sorry bum out there at night and do it then.

Autozone checklist shows the sensor should be between 5 and 25 ohms (didn't say at what temp) but I don't know how much faith I have in their evaluation checklist... not that I have anything against Autozone... they're friendly and helpful at this location.

By Autozones standards, the O2 sensor is shot and the wiring is bad on the truck... but again I'm not sure how much faith I have in thier list.

Thanks
Okay, I'll quit my whining... I checked the resistance on the O2 sensor after the engine cooled overnight... actually it was pretty cool to the touch. It was about 7 or 8 ohms.

I think the sensor is good.
 
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