Can Shaft Position Sensor

Discussion in 'Gen 1 & 2 - Emergency Issues - Help & Maintenance' started by Craig, Oct 16, 2020.

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  1. Irish Pride

    Irish Pride Irish Inside Staff Member Super Moderators

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    Why did you replace the DIS module 3 months ago? Because of this problem or something else? Is it a Ford/Motorcraft DIS or aftermarket?
     
  2. zoomlater

    zoomlater SHO Member Supporting Member

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    I would think the new cam sensor would not go bad that quickly. When the cam sensor is disconnected, the computer has to guess if its lined up correctly to start. That is why it may take a few tries to start it. Once its started, it supposed to stay running.

    As Irish Pride asked, what brand DIS did you install? Did the person who replaced it put heat sink paste on the back side of the DIS and secure all four fasteners to the crossover tube. The DIS generates heat and needs to dissipate the heat to the crossover tube. The fasteners are part of the grounding as well.

    The latest problem I had with my 92 is it would just die on the freeway and when I took my foot off the gas. I had no codes for longest time until it finally threw a DIS code after 6 months (and after I changed out my throttle position sensor and Idle air control valve). I haven't had any issues since. A slow failing DIS module.
     
    Last edited: Oct 20, 2020
  3. NoSlo

    NoSlo GoldMember

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    This is all there is to the ignition system:

    [​IMG]

    The only thing not pictured is the grounds, and the power to the computer, which comes through the CCRM.

    There are multiple sensor failures that can make the engine buck and lurch, such as O2 sensors or throttle position, but they won't completely kill the engine. Oil in spark plug wells can also make the engine buck, as it will kill two cylinders at a time and seems to happen more when hot and when the engine is not revved up. The crank sensor or DIS ICM usually fail first by dropping out for fractions of a second at a time when hot, until they completely stop working when hot, and then completely stop working period.

    If the power from the CCRM or grounds are intermittent, then you also have an "instant off" feeling, just like when the crank sensor dies. Wiring faults shouldn't be affected by heat, but instead happen from vibration, and CCRM is minimally affected by heat.

    I'm curious what you mean by "The tach idles at about 5 or 6 k". You mean the engine revs to 5000 RPM when you simply turn the key to start the engine? Or you need to push the gas pedal? And then you say that the engine died when coming down a hill, not idling or accelerating - the engine can't die if it is in gear, but it can stop making power.

    Given the weird and inconsistent symptoms you describe, I might first investigate and replace the IAC - idle air control after checking for spark plug oil. This is a valve that is a horizontal cylinder a bit bigger than a D cell battery, just to the left of the throttle body looking into the engine compartment, attached with two hex screws and a gasket. Its function is to let a little bit of computer-controlled intake air in to keep the car idling and it adds a little bit of power besides the gas pedal. If you have a car that won't stay idling, or intermittently idles high, it may be that the valve is sticking, alternately sticking wide open or sticking closed. It can be cleaned out by spraying and soaking with carb cleaner, but this may not solve all problems with it, and to eliminate it as a potential cause if the symptoms match, it should be replaced.

    Unfortunately, if you continue to get dying even when accelerating, like someone turned off a switch, and engine codes set after the failures, crank position sensor is the most suspect but the most work. If you've not replaced the water pump at the scheduled 60k, water leaking on the sensor can cause intermittent problems or can permanently damage the sensor.
     
    Last edited: Oct 23, 2020
  4. Craig

    Craig Member

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    Let me back up a little. About a year ago, I had a problem that no one seemed to be able to diagnose. The symptoms were wild and confusing. Finally someone pointed me to a country mechanic who some people around here called a legend. Anyhow, I took the car out to him.

    It took him awhile because he is used by all the car dealers and garages in my area when they run into problems they can't figure out. He found that the crank gear was disintegrating and was amazed that the car kept going. He fixed the car, showed me the gear, and charged a welcomed price.

    In the process before getting to him, the mechanic I was working with said he had examined the car using his diagnostic capability and replaced 2 parts including the mass air control sensor and fuel pressure regulator. I hope I remembered those names correctly. I haven't had time to examine my records. I also had him replace the O2 sensors because they had never been replaced.

    On the idle, in my car whenits running right, when I start the car the tack goes right to 8900 or 9000 rpms and is very stable. With this problem, when I start the car, the tack idles at 5 or 6k. Also, with the sensor connected, the car only dies a couple times at most when I try to start it. Its a little hard to start. But when it starts it does not die. It just runs rough.

    I replaced the DIS module myself with a Motorcraft part using the heat sink material. The lower right screw was missing. I got a replacement screw and put it in. I replaced it because, the DIS that was in there was the one that came with the car.

    I have not replaced the PCM.

    I had the crank position sensor and water pump replaced because the water pump was leaking on it. And I've replaced the cam shaft position sensor 4 times since I got the car and will have to do this one again I'm sure. And the crank seal has been replaced. It was pinched. The people that fixed it, in a bigger town some distance from me, showed it to me.

    There is a wisp of oil on the spark plug wires in the front. I can't reach the back, but I know the valve cover gasket in the back is leaking. The wells in the back, for that reason, I guess might have quite a bit more oil in the wells. That could be part of the puzzle.

    I'm leaning toward a serious job with the country mechanic including valve gaskets ( valve cover gaskets will be replaced I would think), cam sensor with cam seal, and examination of the front and rear main seals with replacement if needed. If the car is still having a problem, the crank sensor would be next. Any other suggestions while I'm doing all this. What do you all think? I'm on a pretty fixed budget, but have been saving in this direction for awhile.
     
    Last edited: Oct 22, 2020
  5. luigisho

    luigisho SHO Member

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    9000 rpms would be beyond the capacity of the car to reach without a full gas pedal mash and (since I've never had a car that high) probably would cut off without a workaround. So I will assume that you are seeing 890-900rpms which is close to normal and 500-600 rpms at idle is very low and might make the oil light flicker. I forget the rpm where it sets off.

    There are alot of DIY write ups on how to replace the seals and gaskets up top if it was something you might consider. If the ignition is misfiring due to oil in the front or back banks, that could be the difference in idle right there. New gaskets, plugs, wires and you might be good to go. Just be methodical, label everything and you can tackle this if you have the time and the gumption.
     
  6. Craig

    Craig Member

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    I've been wrong about the rpms for a long time I guess. Thanks for pointing it out. Although I've had the car for a long time and have learned some things and even replaced a few parts myself, I've tried to find people who can do the work. I'm more of a driver who likes the car, but doesn't know much about cars. I do appreciate the complexity of these machines and their amazing service.
     
  7. NoSlo

    NoSlo GoldMember

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    Normal idle is 900 RPM. If it sometimes drops to 600 or lower, then either the IAC is not properly maintaining idle, or you likely have a misfire, such as spark plug oil, bad plug, shorting plug wire, or bad coil. The misfire will have much more engine vibration. 1/3 of the DIS being bad is a very remote possibility. All can be intermittent.

    You can run the "cylinder balance test" at the end of the engine-on code-reading procedure to see which cylinders are misfiring while the symptom is persistent, but I would not recommend running for long at low idle and low oil pressure. http://taurus.heliohost.org/eec/eec.htm


    The cam sensor should remain dry, and you should not be replacing them as a habit. A bad cam sensor will also have the tachometer cutting out and dropping to 0 while the engine remains running. If oil gets inside of it, then that camshaft seal is leaking. You'd also have oil leaking to the ground or onto the catalytic converter making smoke, unless the mechanic did something dumb like sealing up the sensor with RTV (opposite: drilling a drip hole in the bottom to let out oil).

    The cam seal installation is not a simple task, one must not scratch the camshaft or damage the seal while installing, which requires a seal spreader and seal installer to ensure success. The camshaft seals are part of front 60k, which is everything behind the timing belt (including the crank timing cog, that if not torqued properly can damage the Woodruff key and spin).

    Replacing valve cover gasket and spark plug seals are the upper 60k service. While inside the valve covers, one also adjusts the valve gap with shims. If the plug wells fill with oil or oil is leaking down the front or back of the engine, it is time for this as well, but it is separate from everything you've described.

    (this is why the only mechanic that has touched my engine in 17 years of ownership is me...)
     
    Last edited: Oct 21, 2020
  8. BaySHO Performance

    BaySHO Performance SHO Member

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    You are going to have to replace the camshaft seal behind the camshaft sensor. It's leaking and contaminating the sensor. So get a new sensor and a National 1213N seal from O'Reilly.

    You will have to remove the torque limiter from its bracket, the bracket itself and upper timing belt cover (to get a better angle for when you lever the seal out). Unbolt the power steering reservoir and secure it out of the way at the rear of the engine. Lay some paper towels below the sensor so that no bolt can disappear into the rear engine mount, never to be seen again.

    Then the cam sensor (7/32" socket), sensor O Ring (8mm) and semi circular vane behind it. Tap a thin long bladed screwdriver (without burs that could cause scratches) between the inner seal lip and camshaft. You will probably find that the first screwdriver won't be stiff enough, so keep on going bigger until the tool is stiff enough.

    Put plenty of grease on the inside and outside of the new seal, and on the camshaft itself. Use the cam sensor O ring to draw the seal in, but make absolutely sure the seal goes in straight, otherwise it could jam and crack the O ring. This will get the seal in part way, but it will need to be pushed in further.

    So you will need a 2 1/4" id x 1 5/8" plastic ring from the plumbing department at you local hardware store. Pic shows it as part of my intake cam seal installation tool:

    IMG_20201003_111707464_HDR (1024x928).jpg

    Use a large washer over the end of the plastic ring and push the seal in further by levering against the strut tower. I use a 2" pipe for that.

    The final step is to insert the square end of a 1/4" extension bar to make sure it's fully seated and in straight. The square portion should go all the way in and stop at the rounded portion. Use the bar to push it in further if necessary.

    However, if the car still misbehaves, it could be the DIS module itself, so check it out.
     

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  9. Craig

    Craig Member

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    Thanks everyone for your time and help. Your knowledge and skill is appreciated. I've enjoyed this car. I got it in 1990 with 10K miles on it and its been a daily driver. I hope I can resolve all this.
     
    luigisho likes this.
  10. zoomlater

    zoomlater SHO Member Supporting Member

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    I never really worked on my cars before I got a SHO. There is a lot of owner experience with the issues on this car that has been documented on this forum. Majority of the time, you can search and find answers on what is going on with your car. On a side note, if your mechanic messed up the fasteners, etc. during the last cam sensor replacement, the photos that I had attached came from a NOS part that is for sale on ebay. Spark-surplus has been a good source for a lot of SHO parts over the years.
     

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