[tamathumper]

I called and spoke to a very helpful "Jamie" at 944Online, and he said the original pins will stick right into the back of the connector they have and "click" in.



So, I'm going to buy that connector and that will resolve the crispy issue.

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[flash]

good deal. i can't remember where i got mine, but that might have been it.



double and triple check the orientation of the wires. change them one at a time if you can.

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[MB968]

Here's another source for a kit:



http://www.efiexpress.com/catalog/produc...fccdca4679



I didn't see a source for each of the individual pieces of the connector, though there has to be one.



Also check out the cam position sensor shown on the same page. It plugs in between the sensor and the wiring harness and has the diode/led built into the one connector.

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[tamathumper]

A confusing mixture of terms between all these sources. One site recommends to use a 3 V diode to test the CPS or "crank position sensor" and this site here recommends to use a 5 V diode to test the CPS or "cam position sensor". I think of course they are referring to two different things, the 3 V is for the DME plug and the 5 V is for the hall sender.

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[MB968]

Tama, the crank pos. sensor is a passive device and I think thus its output is lower in voltage. I know the wheel speed sensors for the ABS which is essentially the same as a crank position sensor has an output of a fraction of a volt up to about 3 volts.



I believe the cam pos. sensor is a 5 volt powered sensor, thus the higher voltage requirement. (I know of them, but I've never really worked with hall effect sensors so I could be wrong).



And, I'm pretty sure both sensor yield an AC signal, thus the use of the diode to convert to dc volts for use with an led.

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[tamathumper]

OK, male connector purchased from 944online.com. The female side is in good enough shape that I can't bend or break it with my hands trying really hard, so I'll just buy the male half for now. Can't seem to get an LED to light up on that thing, no matter which wires I try. I'm using a 3V on it, but I probably should have used a 5V (lucky I have spares).



Second test - I stuck the hall sender cables back together and pulled the DME relay. When I cranked the engine, the tach needle jumped once to 500 RPM and again to 800, and then went dead. It did this four or five times. Then it came to life and bounced to about 1500 RPMs a few times, but it was erratic. It bounced high and low and then not at all, so I'm guessing there is something amiss with the sensor that's buried under the intake manifold. How the *heck* do you get to that thing?!



UPDATE: I ran the engine for a few minutes. Severe hesitation when "blipping" the throttle. Blink test shows a clear 1-5 cycle...

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[flash]

unplug the sender and see if it goes back to how it was before

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[tamathumper]

Not sure I follow, it *is* back to where it was before. The severe hesitation was part of the original symptoms.

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[banditsc]

If the tach doesn't work and you have a no start condition, it's the crank sensor.

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[flash]

i mean DISCONNECT the Hall Sender. it was disconnected before. it is connected now. the symptom as described is different than previously described. disconnecting that and restoring the previous condition is the only way to tell if your new connection is causing your new symptoms.



severe hesitation when you blip the throttle indicates a vacuum leak. install a gauge between your MAF and your valve on your test device, and read the pressure. also have a vacuum/pressure gauge attached at the vacuum source up at the fuel pressure regulator. you cannot use the gauge on the compressor.

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[tamathumper]

My Hall Sender was never disconnected - sorry if my previous posts implied that. On the previous page I described how the plastic connector crumbled apart when I touched it, but even still the pins were somehow all fully seated even then.



If you think it's vacuum-related, I'll fire it back up and put that new vacuum gauge to use. And buy a crank sensor.

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[flash]

i think it essentially was disconnected, in that it was not working. given the condition it was in, i find it suspect. unplugging it and giving it a go will tell you. if there is any change, then you have found a problem.



never assume anything when trying to diagnose a problem.



yes, please put the gauge on there and watch what is happening with the system disconnected from your compressor after you charge it up to 5psi.



are you listening with a hose in your ear? vacuum leaks are often inaudible in ambient situations, and can only be heard with a hose or something like that.

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[tamathumper]

OK, Hall Sender connector is repaired, and all of the hoses are adjusted and clamped tight (visually checked). Still need to re-test with air pressure. That connector is a good fit, but you have to remove a little bit of the plastic at the back between the wires to help them go all the way in, otherwise you'd have to remove part of the cable sheathing, and that's not safe with those tiny, toasted wires and the small amount of room you have to work in there. You also have to remove a little plastic tab in the portion that slides into the metal bracket, otherwise it won't go all the way into the bracket and you can't get the little metal retainer clip back in.



Car still stumbles hard, with one backfire, and there is no tach bounce at all. Car runs the same with or without Hall Sender connected.



Edit: Can anyone verify what the tach needle does when cranking the car with the DME relay removed? I want to make sure it's supposed to jump (and how far) before I tear into that Crank Position Sensor - it's *buried* down there!

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[MB968]

Tama, did you ever do a multimeter check on the crank pos. sensor?

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[tamathumper]

I just did a multimeter test on the old and new sensors. Both tested identically, e.g. testing for 1K Ohms the meter showed no resistance using pins 1 & 2 (or 2 & 3, I don't recall now) and had no response between any other combination of pins.



The new sensor was smooth, while the old sensor had a dimple on the end and I figured it might have gotten knocked by something in its lifetime, so I put in the new crank sensor for grins, and I still have no tach bounce at all and severe hesitation with throttle "blips".



I re-pressurized the system and I can definitely hear a hiss that sounds like it's coming from down under the exhaust manifold somewhere, but using a hose to my ear I can't for the life of me find it. The green and orange vacuum hoses that go into the firewall seem fine - I can get a hose on them from all angles and there's no hiss coming from them. The heater control valve likewise seems fine. There's one section on top of the throttle body I'll change out because it will hiss if I push on it just right, so I know my hose method works, but I can hear this hissing down under and behind the engine even without the hose, I just can't seem to find it! Is there a vacuum fitting on the engine down there somewhere?

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[tamathumper]

Video of startup and stumble/hesitation, accelerator is pressed four times and there is a "chuff" for 1/4 to 1/2 seconds then the RPMs rise. Idle is a bit high which is abnormal - might be because of the vacuum leak I can't find?



http://www.youtube.com/watch?v=AgIp8vzuD4U

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[banditsc]

Has your intake manifold ever been off?

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[MB968]

Have you checked the continuity of the crank pos wiring back to the DME? Even if the sensor is OK, you could still have an issue in this wiring.



From your comments, I'm assuming you don't have a vacuum leak significant enought to cause this issue. So, couple other thoughts.



The rate of change of the trottle position sensor is typically used by the ecu to give an extra shot of fuel when the ecu sees the sensor output change rapidly (for you math guys, it looks at the derivative of the signal). If you're old school, this is what replaces the accelerator pump. If the ecu isn't seeing this, it will not give the enrichment that is suddenly needed when the throttle plate is opened. The engine will run super lean for a brief time, and will hesitate to respond and/or may stumble.

The <acronym title='throttle position sensor'>TPS</acronym> is basically a variable resister. Check the manual, I'm sure it is easy to check with a multimeter. I'd first just check the wiring/connection.



Also, once on my Mazda, when I forgot to connect the mass air flow meter, I had a similar stumble with any throttle change. I don't know how to check this unit, but I think issues with it could lead to stumble. Although I think this would give a different end result, as I don't think the engine would ever catch up. Seems like yours hesitates/stumbles, but then eventually responds.



As always, take them for what there worth. Good luck.

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[flash]

what does the durametric say?

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[Cloud9...68]

Tama,



As far as the tach bounce when cranking the engine without firing (e.g. when you have the DME relay disconnected), mine bounced pretty sharply from around 0 - 4000 rpm indicated, at regular intervals (as the gaps and teeth of the flywheel passed in front of the sensor's magnetic pick-up). If you're not getting that kind of bounce, I would definitely suspect your CPS.



As far as the throttle position sensor, it's pretty easy to check. Here's the procedure I followed back when I was having my hesitation problem (which turned out to be a bad set of aftermarket plug wires) many years ago:





The 944 throttle position "sensor" is really just 2 switches. an idle switch, and a wide open throttle (<acronym title='wide open throttle'>WOT</acronym>) switch. It should really be called a throttle position SWITCH. That test procedure you provided a link to tests the function of the 2 switches.





The 968, like most all cars uses a true throttle position sensor. A variable resistor that can read out to the ECU the exact position the throttle is in.





Turn the ignition on, but don't start the car. You'll have to have some type of voltmeter probes that can make connections without unplugging the connector. Usually you pull the boot off the back of the connector, and push the probes in there. You should find 5V on pin 2 (the blue/green wire) pin 1 should be ground (the yellow/brown wire) and pin3 is the output (the white/green wire). To test, you should hook the voltmeter between pin 1 and 3. as you slowly open the throttle, the voltage should go from about 0.4V to 5V with no abrupt jumps, either up or down. Abrupt jumps are a sure sign of a bad <acronym title='throttle position sensor'>TPS</acronym>. An old, analog voltmeter is MUCH, MUCH better at seeing intermittent jumps than a digital one, but who the heck has one of those.

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