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3.2 Can't Hold idle sounds like a cylinder missing

Discussion in 'Mondial' started by moysiuan, Apr 12, 2020.

  1. Jeka

    Jeka Formula 3
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    In the prestart phase the mixture should be richer. By applying 1.5 Volt = 1.5/200 = 7.5 mA the mixture is richer, this acts like a choke. If the voltage you measured is lower then the mixture shouldn't be too rich as in your case. The only conclusion is that the current is not max negative or positive and the motor starts around the basic adjustment. It looks like the controler is not the cause. Although you have to electrically disconnect the actuator (= pressure adjuster) to be sure.
     
  2. moysiuan

    moysiuan Formula 3
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    Ok, measured again and get the 1.5 volts. I am starting to think all this is going to come down to cleaning all electrical contacts.
     
  3. moysiuan

    moysiuan Formula 3
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    Test disconnected the actuator after warming the car up, car runs fine. Car now running well enough to do tests 19 through 23. Test 21 at 1 mV, test 22 ocilating at about +15 to -15 mV. I can get this range to change by adjusting the mixture screw, I presume getting the tightest range +- around zero is ideal?

    Only measurement now confusing me is the throttle position sensor jumper test in test 23. Not getting the 100mV, getting more like 1mV. ??
     
  4. Jeka

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    That all seems good, the voltage of test 21 should oscillating around 0 if the basic adjustment is good. Open throttle will bring the controller in open loop and apparently the actuator slightly richer (100 mV/200 ohm = 0,5 mA). 1 mV should be oke, it's at least not the cause of an overly rich mixture.
     
  5. jgoodman

    jgoodman F1 Rookie
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    There’s all kinds of good suggestions going on here. May I suggest you take a step back and check some things that can cause loss of power or more commonly intermittent loss of power. The spark plug extenders are notorious for getting tiny arc spots on them that short circuit the charge to a spark plug. It presents as a pinpoint dot on the side of the extender. It’s very difficult to see the “short” however these are very easy to replace. The other thing that likes to go bad are the coil modules. They too are easy to replace. Replacing the battery is an easy option as well. The final thing that can cause intermittent power loss is a bad cat. Fascinating how a car doesn’t work right if the exhaust gases can’t get out. Remember that these are old cars and all of these are wear items that can be causes of intermittent power issues.
     
  6. moysiuan

    moysiuan Formula 3
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    All good thoughts, but my car is overmaintained by me, and all the plug extenders, coils with modules, battery etc. are near new. I swapped old good parts for the new ones to rule out some of these items definitively, indeed I spent alot of time expecting the more common causes of the problem to surface, and was focused on spark as the symtpoms presented like missing cylinders. But after ruling out spark, I shifted to fueling issues. It appears overfueling is the root problem, fouling plugs, which then made it appear like spark problems. The focus of much of the thread has been on how to do the various volt/ohm meter tests that allows for diagnosis of various of the fuel system components. This has been exceptionally helpful in avoiding swapping out parts needlessly. Narrowed things down but still not sure what the problem is. Certianly I have a fantastic understanding of how the KE3 system works, which is the Swiss market only Mondial fueling system, not the standard KE found on most Mondials.

    That said, I might have solved this through all the various connectors having been meticulously cleaned and it is possible the cause was electrical faults, but since the problem was somewhat intermittent, I won't know until I put the car on the road for a while. Since I am going to proactively replace a couple of things with parts on order, my car will be laid up for a while longer. As of yesterday I did seem to get the car to run and idle well for an extended period of time. I would prefer to have found an actual identifiable problem, so I remain suspicious that I still have an intermittent issue that went into hibernation yesterday.

    One thing that surfaced through this thread on electrical diagnostics was that my O2 sensor was blocked by a fuse, presumably left in by the prior owner's Ferrari dealer when setting emmissions, meaning my car has been running without the lambda since I have owned it for 15 years! This despite meeeting e tests every two years, and the car running well over a long period of time. It does mean my car was likely running rich most of the time, and although I had put on a new Fabspeed sport cat about 20,000km ago, it is possible that the rich mixture over time has gummed up the cat. So that is something I will investigate further as well.
     
  7. spicedriver

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    It might be worth it to pull the injection ECU from the car. Set it on a work table with a bright light, and a magnifier. Remove the covers and visually inspect the PC board. You're looking for corroded traces, bad solder connections (especially grounds), bulging capacitors, and burned components. Use your multimeter to check for shorted transistors/diodes, and open/off value resistors. Also, the various inputs to the ECU should be tested at the relevant ECU connectors.
     
  8. moysiuan

    moysiuan Formula 3
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    I am curious if test 21 can be used to set the mixture, ie. if I richened the mixture adjustment the voltage tended towards ociliating to the positive voltage witnin a range, while leaning made it ocilate to negative voltage, and with small adjustment the swing between positive and negatuive by about the same max amount seemed to correspond to the car running most smoothly, and that's where I left the mixture setting. I will check mixture in due course properly with my CO meter, but I am wondering if this test reading is an alternative way to optimize mixture.
     
  9. Jeka

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    As a course adjustment that should be possible if you are sure the lambda probe is good, there are no exhaust leaks and the motor is fully warmed up. If not, there is a risk of compensating for other faults. An idle adjustment followed by an open loop adjustment using a CO/HC meter as described in the manual is better I guess. It's a good sign the car is running most smoothly with an even swing between positive and negative, the controller seems fine. Maybe the basic adjustment was out of spec which was not corrected by the open loop?
     
  10. moysiuan

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    Put in new fuel regulator, problem still there. Put in new cold start injector. Problems remains. So definitively ruled out those items. That cold start injector on the back of the plennum wwas pretty tricky to get at.

    Will also be putting in new crank sensor, looks like a tough job, getting a magnetic socket on order as per another thread. Need to rule that out, it is not an uncommon cause of the type of problem I describe.

    Pretty much exhausted the more basic ecu tests, will take apart and look/test for flaws as noted. Some new relays on order for greater certainty.

    I am now coming to grips with the possibility of the fuel distributor leaking internally. Contacting a rebuilder to see what the options are.
     
  11. Steve Magnusson

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    Didn't you report that with the EHA unplugged (i.e., the EHA current forced to be 0 mA), it runs fine when warm? If so, that confirms that the trouble is not the fuel distributor.
     
  12. moysiuan

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    #162 moysiuan, May 14, 2020
    Last edited: May 14, 2020
    It did, and then it doesn't, back to the same problem. What is stumping me is I would expect that whatever is causing this would do it all the time, not be intermittent like this. Car seems to run for a while, even drives well enough for a while, then idle drops, sounds like a number of cylinders not firing and eventually the car will stall if the gas peddle is not tipped into. Then won't start, although that looks like it is due to the plugs fouling, once I replace the plugs it starts again. I am going through alot of plugs...Something is just not giving the car the proper fueling. When the car is running poorly and barely able to idle, disconnecting the EHA makes no difference. When the car was running well enough, and warmed up disconnecting made no difference. I am still focussed on the fuel ecu as a problem, as that could explain intermittent issues when everything checks out on diagnostic volt and ohm tests, and I have a new one on special order. But I am really just becoming a parts replacement monkey, I would prefer to be actually identifying what the problem is!

    I still have the original fuel pump. Is there any way this pump is causing the problem, I don't understand how it could, either it is pumping or it is not, I would not expect anything intermittent, and I associate fuel pump problems with the car not starting?
     
  13. moysiuan

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    So maybe this helps with diagnosis. I received a good used spare igntion microplex today, and after cleaning up all the various connections, including what I can see as grounding items in the the same area as the microplex, I did the various tests 1 through 12 in the Service Bulletin for my MED806 A unit. I did the same tests with the old and new units in the car, the car was running not well the same regardless of the unit.

    All the tests were in spec, except crucially, I can not get the voltage readings on tests 8 and 9 being the voltage for the TDC and Tachimetric pickups. After having replaced the plugs and done the tests a few times to make sure I am getting the correct pins, and getting good contact, I am as sure as I can be that there is very low .oo3 volts or no volts depending on when I measured. I have checked and cleaned the wiring harness pins, and various connectors that the main microplex connector attaches into the main wiring harnesses. No voltage. How can this be? The ohm readings for the two sensors are in specification. The tach sensor I put in is new, but even it is not generating the required voltage. Is there some relay that deals with all this?

    Also, test 12 being the output signal to the tach was in spec, but I am sensing that the tach is not reading proper, seems to be reading lower than actual rpms. Never noticed this before with all the other tests I have done, but then I did not play with the air idle bypass screw as I did this time, as I wanted the rpm up a bit to ensure the car ran well enough to do the tests.

    Any insights on all this?
     
  14. Steve Magnusson

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    Are you sure the multimeter is on V AC (and not V DC)?
     
  15. moysiuan

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    Well that's embarassing, good catch.
     
  16. spicedriver

    spicedriver Formula 3

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    Perhaps the plugs have already become fouled at that point ?
     
  17. moysiuan

    moysiuan Formula 3
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    So here is the odd thing as I do voltage checks on the microplex. My original microplex unit reads .576 volts on the test 12 being the output signal to the tachometer. The new (used) replacement microplex reads .25V, which is in line with the specification. But the car tach reads lower on the new microplex, while the old one seems to give rise to the correct tachometer rpm readings (in both cases the actual engine rpm sounds the same).

    Both microplexes test the same on all the other tests, and all are in specification. Just the output tach signal is the anomoly. Is this some sort of useful clue to nwhere I have a problem?

    Also with the EHA unplugged after the car is warmed up, the idle seems to smooth a bit and a slight surging is no longer in the idle verses when connected.

    I also note there is a voltage check for the tachimetric pick up, but not a test for the crank position TDC sensor pickup? Is there an AC voltage test for this item? The AC volt on my tach pickup, did read in spec once I realized the DC voltage setting on my meter was incorrect.
     
  18. Jeka

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    I do not have the specifications of the Microplex unit. I am not sure if the tach output is a DC voltage. If the tachometer output is a pulse, you need an oscilloscope (or frequency counter) to perform the test. Is there a big difference in tachometer reading between both units?

    With the EPA unplugged the surging should be less because it's free running the without feedback.
     
  19. moysiuan

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    The spec calls for the tach output to be DC voltage. The tach reads about 1/2 on the new unit, while the old unit reads a correct rpm, as measured by an external tachometer reader.

    The microplex units are both the Marelli MED806A units.
     
  20. moysiuan

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    Since there is no voltage check for the crank position senor (unlike the tacometric one), I am going to replace it to rule it out. It is very difficlt to get at, had to remove various crankcase vent hoses and othetr things just to get at the nuts, the hoses themselves were really hard to get off.

    Eventually removed the nuts, but the sensor appears stuck on, probably the metal and aluminum has corroded. Not sure what to do here, the darn things is inset in a little well in the casting, which probably collects moisture, and unlike the surface mounted tach sensor whic is surface mounted on the casting prying it off, even with access improved by removing the rear distributor cap, looks challenging.
     
  21. MvT

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    Best way is to get to it is via below behind the wheel. Don't spray it with WD40 ir stuff like this, else it will get into your clutch. The challenge is to wiggle it out without braking the sensor. If it does it often falls into the bellhousing with all the extra work included meaning to take off the bellhousing. There are many to whom happened this unfortunately. If you'll be carefull it should work out.

    Removing the distributor cap(s) will give you more workspace. Cannot remember if I took them off though..
     
  22. Steve Magnusson

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    Yes, Test No. 8 of Service Bulletin 80-28. Should be greater than 0.1V AC (IIRC, the TDC sensor on my TR measured about 0.2V AC, but a TR has 3 pulses/rev vs only 2 pulses/rev on the V8s).
     
  23. moysiuan

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    Voltage measured in spec fo then sensor. But I feel this part needed to be changed out to rule it out definitively, there are other threads where the sensor resistance and volts measured correctly but the car wouldn't run properly until it was replaced.

    Well, my tdc sensor is stuck. Lots of wiggling, but I think it is going to break off, the plastic is now wiggling, but the metal plate is fixed solid. I am pretty sure if I keep wiggling it is going to break. I tried tapping on it, levering it a bit with a long screwdriver, it is not budging. It is so tight to work in there, even with the dist cap off, and the well makes it unlikely one can lever the thing in any meaningful way. I am pretty much resigned that it is going to break and the underneath piece fall into the bell housing. :( Punching it out from inside the bellhousing may be the only way to get it out. Oh well, one project leads to another...

    I presume there has been galvanic corrosion that has welded the metals together. Anyone tried to drip some muriatic acid or something similar on this to break the bond? This darn sensor should just have lifted off once those nuts were removed. There is no obvious sign of corrosion.
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  24. jkstevens2

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    I am sorry.....I can't let this one go. I have to know how this epic novel turns out. ..........Did Agent Moysiuan retrieve the radioactive tachometer tdc sensor head out of the flywheel housing before the beautiful red head was eaten by the shark? Or did the smoke screen generator ignite the o2 sensors and send oddjob over the cliff? Please continue with this nail biting story.....
     
  25. moysiuan

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    Project stalled, delivery delays on the boroscope. Also looking into parts availability, appears a new flywheel for my car may no longer be available, so makes me more cautious on how I may deal with this.

    Rest assured I will prevail, that sensor bit will regret ever taking me on. The old Greek gods are just toying with me.

    Of course, this is all part of solving a more difficult to pin down engine fueling problem, and for all my sensor drama I suspect the original sensor was actually working. This replacement was simply to rule it out definitively before going ever deeper down the diagnostic path.
     

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