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Gas engines do the same thing.

If the vehicle is equipped with a MAP sensor, under a constant throttle condition (cannot be WOT), flow of the EGR is checked by opening the EGR valve all the way.

This admits EGR to the intake manifold which causes the intake manifold pressure to rise (vacuum goes down). The PCM looks for that pressure increase through the MAP sensor.

It can distinguish between plugged passages and an actual faulty valve because the valve itself has a lift sensor built into it.

Same principle with an MAF equipped engine.

Under constant throttle, the valve is fully opened. You see a corresponding drop in airflow into engine when this happens.

Now, even though our trucks have MAP sensors, we don't have throttle plates. So the MAP cannot be used to check for EGR flow because their would be no corresponding pressure change in the manifold when the valve is opened.

Make sense?

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I think so..... If I got it correct, what you are saying is that the MAF is sensing that less air is being sent past it. But further, if that is correct, then technically speaking, it is not actually reading the EGR, but rather supplying data that helps the PCM decide if the EGR is, or should be, open(ed) or not. Though it looks to me like the EGR would have to do it's thing independent of the MAF first (albeit probably nanoseconds first), in order for the PCM to read a drop in the air flowing past the MAF.

Even if I misinterpreted what you said, it looks to me like a faulty/dirty MAF would skew the PCM's calculations. And given that there is oil being sprayed into that same tube by the CCV, it seems like it would be possible for the MAF to get coated with a thin film of oil, raising the possiblility that the MAF could give a faulty reading to the PCM...... Of course, I could be entirely wrong too......

Nonetheless, thank you for explaining this for us!! /ubbthreads/images/graemlins/biggrin.gif /ubbthreads/images/graemlins/biggrin.gif
 
Though it looks to me like the EGR would have to do it's thing independent of the MAF first (albeit probably nanoseconds first), in order for the PCM to read a drop in the air flowing past the MAF.

Even if I misinterpreted what you said, it looks to me like a faulty/dirty MAF would skew the PCM's calculations

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I am not trying to speak for Fordmechanic, his explanation of the MAF sensor is totally correct.
The EGR valve is electrically activated by the PCM, when this happens the PCM watches the MAF sensor signal voltage, which is a variable voltage that changes with more or less air flow. The PCM watches for the MAF voltage to fall into a set parameter that has been calculated into the PCM programming. If it does not, then its supposed to turn on the check engine light. Its all part of OBDII generated by the EPA. As for oil fouling the MAF sensor, I believe this is a possibility, and could cause a false trouble code related to EGR. Please correct me if I'm wrong Ford Techs, but this is how it works on the foreign cars that I work on.
 
See if this makes sense to you, I am quoting myself from another...

[ QUOTE ]
The MAF signal is used to calculate exhaust gas recirculation (EGR) and for fault detection. Basically, EGR flow is estimated based on the difference between the Mass Air Flow (MAF) sensor reading, and, the total mass flow calculated by the speed density calculation. The estimated EGR flow is then compared to the expected EGR flow to determine if there is insufficient or excessive flow. This actually serves as a feedback mechanism to verify that the EGR emissions system is operating properly and it is also a function of the OBD 1&2 Systems and Comprehensive Component Monitors.

Now, if this sensor is providing biased readings they would have to be way off to be considered out of range and set a code or even have an effect. The only trucks I have heard of having a problem with this sensor are those with aftermarket "performance" intake filters due to contamination or airflow characteristics.

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That ought to confuse the heck out of you! /ubbthreads/images/graemlins/biggrin.gif But it is technically accurate as applied to the 6.0L.
 
[ QUOTE ]
See if this makes sense to you, I am quoting myself from another...

[ QUOTE ]
The MAF signal is used to calculate exhaust gas recirculation (EGR) and for fault detection. Basically, EGR flow is estimated based on the difference between the Mass Air Flow (MAF) sensor reading, and, the total mass flow calculated by the speed density calculation. The estimated EGR flow is then compared to the expected EGR flow to determine if there is insufficient or excessive flow. This actually serves as a feedback mechanism to verify that the EGR emissions system is operating properly and it is also a function of the OBD 1&2 Systems and Comprehensive Component Monitors.

Now, if this sensor is providing biased readings they would have to be way off to be considered out of range and set a code or even have an effect. The only trucks I have heard of having a problem with this sensor are those with aftermarket "performance" intake filters due to contamination or airflow characteristics.

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That ought to confuse the heck out of you! /ubbthreads/images/graemlins/biggrin.gif But it is technically accurate as applied to the 6.0L.

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LOL, the funny thing is, I know what your saying. /ubbthreads/images/graemlins/biggrin.gif
 
Sorry Ford Doc, I haven't kept up on my training much on the new models. <sigh>

Honestly, I don't work on these much anymore. /ubbthreads/images/graemlins/biggrin.gif This is a good thing. /ubbthreads/images/graemlins/biggrin.gif

I see exactly what your saying, just like the 7.3 infers airflow using a speed density calculation. Essentially a calculation derived from engine RPM and manifold pressure the 6.0 does too for fueling purposes. As we noted above.

So whatever the inferred airflow # is between the factory calibration and the actual airflow through the MAF, the difference between the two is the amount of EGR flow.

Teamroper, think more simple. If I am sucking air through a hole har har.... and I open up another hole in between the vaccum source and the first hole, you would expect to see airflow decrease through the first hole, in the case that were were measuring vacuum in the pipe, we would expect vaccum to decrease if we opened up another hole. /ubbthreads/images/graemlins/smile.gif

Easy enough.

Your saying the 05's use two intake temp sensors, one the intake manifold post-EGR and just looks for a temp change when the valve opens.

How simple and much cheaper than using a MAF. /ubbthreads/images/graemlins/tongue.gif
 
Yes but the MAF equipped trucks do have an IAT-1 sensor, it's incorporated into the MAF sensor itself so that little trick works on all 6.0's and the 4.5 in the LCF for that matter.
 
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Unless you have bidet, that would be advisable /ubbthreads/images/graemlins/wink.gif

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LMAO /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/laugh.gif /ubbthreads/images/graemlins/biggrin.gif Thanks I needed that!

Cary
 
Cool, I'll let my apprentices know...... /ubbthreads/images/graemlins/biggrin.gif

In school right now studying for a new career so I don't even look at the service engineering summaries anymore.

That's a bad team leader, very bad very very bad naughty. /ubbthreads/images/graemlins/vulnerable.gif
 
Surprisingly, it made sense to me..... /ubbthreads/images/graemlins/eek.gif I now think I understand it much better.

Thanks again!!
teamroper60
 
[ QUOTE ]
In school right now studying for a new career...

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You S.O.B.! Your'e getting out? Take me with you please!!! /ubbthreads/images/graemlins/depressed.gif
 
I would if I could brother. Take 1 night class, anything to get your foot started out the door.

Even if it takes you 6 years, just think of where you would be if you had started 6 years ago. /ubbthreads/images/graemlins/frown.gif

You hit the top so quick in this business which is nice because you can acquire some money in your savings and a house when your pretty young, but you get bored.

Then it just becomes a manual labor job instead of a hands on thinking job.
 
Not to change the subject but....is there a way to measure the voltage or whatever mechanisim they use to know that the throttle is open all the way? It ocurred to me the other day that, being throttle by wire, if it's not getting full voltage or whatever it is that tells it to open all the way that could be the reason why it seems down on power. What do you think?
 
There is no throttle plate on a diesel (though some have an EGR "throttle" plate that defaults to wide open). The APP on yor diesel simply tells the PCM how much power is required/desired and the only adjustments made by the PCM for this aspect is fuel pressure (through the high pressure oil system), fuel pulse width and injection timing. The only time those engine fitted with the EGR throtle plate see any action in that system is when the PCM sees a need to "stimulate" EGR flow.
 
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Cleaning it with any type of solvent also removes the coating that prevents dirt from bonding to it.

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Should we just wipe it?
Always used rubbing alcohol. Had a vehical that wouldn't start a customer had towed in. Everyone thought it was a electrical issue a short or fusible link. Pull map sensor poured rubbing alcohol over it and vehical fired right up. Never ever found a bad map sensor. Stealerships ripping everyone off replacing them instead of just cleaning.
 
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