Do I have one problem, or many

I'm at my wits end, and I'm hoping someone here can point the way.
I bought a QuadCab Dakota in 2000. Haven't had much problem with it, other than the PCM module having to be replaced in 2002. Been very
dependable.
But my heater core sprung a leak two winters ago, and I finally got around to replacing it last fall. Note that everything was fine, except for the heater. So I spend a weekend tearing the whole $*#! truck dash out to get to the $100 heater core that could have easily been desined to slip out through the engine compartment. But I'll leave that rant for another thread, as I have another whole list of headaches.
When I got everything back together, the ABS and brake lights stayed on constantly. I assumed something was unplugged, but I couldn't find any problems. Brakes worked, so I drove it.
Now, the engine would die at stoplights. If I hit the gas as it dropped through 600RPM, it would keep running with no problem. If I slowed very gradually with it in gear, so that it tried to lug up to the stoplight, it would keep running. But if I just pushed the clutch in at 1000RPM and let it drop off, the engine would die every time. What's more, as I passed through about 2400RPM, there was a loud 'roar' coming from the engine compartment that would disappear at around 2800. To top it all off, the spedometer wouldn't register speed until I hit about 35MPH. Further investigation revealed that a small vacuum line coming from that 'dongle' hanging off the front of brake booster to the interior was pinched. I had also twisted that 'dongle' while trying to remove the vacuum line going to the manifold.
"AHA! I found the culprit," I says to myself. Either the pinched hose or me twisting the dongle must have broken some sort of diaphram in the brake booster, which let excess air into the intake manifold, causing an overlean condition at the stoplight. This also sucked air through the broken diaphram at a resonant frequency at 2400RPM, causing the 'roar'. Didnt' explain the spedometer problem, but "baby steps", I say.
I spend $100 and an afternoon replacing the brake booster.
The roar is still there, and the engine still dies at stops. So I turn to Google and search for a problem. Turns out there is a problem with a $30 sensor on the rear end that will cause the spedometer/brake light problem. There is also a known problem with the fan clutch that will cause this roaring problem. I would go out and buy all the parts needed, but I find it hard to believe that all these things went bad at the exact same time.
Can anyone here suggest a set of troubleshooting steps or test that I can work through to determine if the fan or ABS sender is bad? Could I have gotten a bad replacement brake booster?
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Easy check for the clutch fan. Drive the truck for a while to get the fan to a normal condition. Then put the truck in neutral and open the hood. Rev the engine up to around 2500 RPM and just listen. The fan should roar at first, after a minute or so it should settle down and be quiet. There are a number of other ways to check it, but this is easy.
Al
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Ernest, Carry your thoughts a bit further. You were under the dash changing the heater core. You were pulling, tugging and pushing everything around to accomplish this most unpleasant task. I think all of your problems are due to this. Yes, there is a hall effect sensor in the rear for the speedometer. In fact, I think there is one on each wheel. The rams have one on the differential as well. They all terminate under the dash. I mean, what can go wrong with an inert sensor. It is only a coil of wire around a magnetic slug. Check for continuity through the sensors from the dash end. It is very likely that incorrect speed data could cause the PCM to create the stalls as well as the brake ABS fault. I would disconnect and examine every pin in the associated wire harness and reconnect carefully. Remember hall effect sensors work by creating a magetic field at the end of the slug and when a metallic object passes trough the field, some of the energy is coupled to that object which momentarily increases the current draw of the sensor. This change in current is detected as the speed signal. Steve

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Steve Lusardi wrote:

Isn't the sensor for the speedometer in the transmission?
The one on the differential is for the anti-lock breaks.
JAM
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Not since '97. The sensor in the rear diff is used by both the CAB for ABS functions, and the PCM for speedometer/odometer functions.
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Ernest Christley wrote:

Welcome to the Dodge Dakota Lemon Club! I have a 2002 that has had some of the same problems and many more. I filed a lemon law suit and got cash for my troubles.
The idle problem is caused by the programing of the PCM. Recheck the wiring connections and clean them, this may clear the indicator light problems and the speedometer problems. The roaring sound is the fan.
JAM
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Excuse me - but when you have a perfectly good working truck, then tear the whole dash out, put it back, and all of a sudden have several seemingly unrelated electrical problems, it's not because the truck is a lemon.

And this programming got changed by him replacing the heater core?
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Tom Lawrence wrote:

That is my thinking on the subject, Tom. The fact that there is such a clear demarcation point for the start of all the troubles really does point the finger back at something I did.
One thing I did not mention, and it may be sort of important. Immediately after I replace the brake booster, the roaring was much diminished, but gradually increased to the previous levels within about and hour. The tone is slightly different now. It stilled died at stopping, but not as badly at first. I really do think the brake booster is involved somehow, but most likely just as a victim.
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It's unfortunate, but I'm thinking you pinched a bundle of wires behind the dash somewhere.
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Another clue:
The dongle hanging off the front of the brake booster has two lines coming out. One goes to the manifold. I assume this is for vacuum. The other runs to a tee and then into the firewall at a couple of places. (The new one also has a capped nipple sticking out the front that the old one didn't have, but I'm assuming it's is a non-player here.)
Do the lines running through the firewall act as a pressure relief system? There is at least one one-way valve right after the dongle (I could blow through it one way, but not the other). I could not blow through the system from the brake booster side after removing the valve. If the pressure gets to high, would it destroy a diaphram in the booster?
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No, the ones going through the firewall are used by your climate control.

These valves are used to maintain vacuum on the brake booster when the intake manifold vacuum drops.

The brake booster is powered by vacuum, not pressure so there should never be "pressure" on its diaphragm. You cannot blow into it because the one way valve prevents it. I would look under your dash and make sure that you don't have a loose or broken vacuum line. The air being sucked through it could be causing both your noise and stalling at idle.
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TBone wrote:

Thanks, TBone. That is on the agenda for the AM. I do remember the line that went through on the driver's side got pinched and I had to rework some stuff to get it back in right. Might have some work to do still.
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