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  1. #1
    Senior Member Array 03yllwcobra's Avatar
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    Default Motor Issues

    Hey Guys, I've been having a miss-fire issue with my car ever since we got it back from the builder. I replaced all the wiring to the coils. I checked that they were all firing with a dummy coil light in line with the plug wire. I then checked them to see how far they would fire across an air gap and everything seems to be the same from bank to bank. To eliminate injector issues I put noid lights on them to see if the were firing and also they are brand new injectors but I wanted to be sure. I did a compression test and the passenger's side were significantly higher than the driver's side. The motor's compression is 10.7:1. The compression is as follows

    Pass-Side
    Cylinder #1 - 255
    Cylinder #2 - 250
    Cylinder #3 - 245
    Cylinder #4 - 255

    Drivers-Side
    Cylinder #5 - 210
    Cylinder #6 - 225
    Cylinder #7 - 220
    Cylinder #8 - 220

    I believe there is a timing issue and have started taking the valve cover of the car and timing cover. I just wanted to ask for a second opinion and to see if anyone had any other ideas.

    Thanks

    Nick

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  3. #2

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    Nick,

    The stock cops have limited ignition energy usually about 20 millijoules. By way of comparison the Mercury Marine IGN1A smart coils produce about 105 -110 millijoules of spark energy. Significantly the spark is a long duration spark of the type supercharged engines like.

    If your boost is in the 20 psi plus range it is possible with the compression you are running, that the OEM cops will be having difficulty igniting the mixture. One of the routes that has helped is the use of smaller plug gaps. The practical limits on that approach are around 0.020", much below that gap the size of the spark kernel is getting too small to completely burn all the fuel in the cylinder.

    The other thing to be sensitive to is the stock ECU. It is fairly good up to about 7000 rpm. After 7000 rpm the slow 25 Mhz cpu pretty much runs out of steam, which can cause fueling issues that would contribute to the misfire problem. My suspicion is you are testing the upper operating limits of the stock ECU and ignition coils.

    In the FWIW bucket the approximately 30 psi compression difference bank to bank suggests different cam phasing bank to bank ó although that will not contribute to the misfiring problem, it can cost you a few hp.


    Ed

  4. #3
    Senior Member Array 03yllwcobra's Avatar
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    Sorry I forgot to add this is with the IGN1A coils and with a Stand alone ECU, I just kind of lost because I don't know what else it could be because I've replaced everything.

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  6. #4

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    That's a horse of a different color, Nick.

    I presume you have already checked all the ECU and coil grounds so the next likely culprit is reduced electrical power at higher engine speeds. Have you data logged the misfires? If you have and the ECU collected voltage data it would be interesting to see the two plots overlayed.

    Any data logs taken that recorded the misfires can be a treasure trove of how come and why for data.


    Ed

  7. #5
    Senior Member Array 03yllwcobra's Avatar
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    Yeah I have a 3/0 wire to the motor mount and a 10 gauge wire directly to the coils, and the cylinder head ground is ground to a intake manifold bolt on each side. I re-did all of the wiring to the coils to the computer and a new relay from leash, new power wires and new plug wires. So thatís why I donít think itís wiring. Is it possible for someone to switch the intake and exhaust cam? I havenít checked the part numbers on the cams yet but is it possible that the car could even run like that?


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  8. #6

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    What conditions are you experiencing the misfire under?

    What fuel? Plugs?

    I personally would ground them to the back of the heads and not an intake bolt.

    Mike


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  9. #7
    Senior Member Array 03yllwcobra's Avatar
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    Default Motor Issues

    The misfire is all the time from idle on. The fuel in the car is E85. Also with the car idling I can disconnect all the injector wires on the passenger side and it doesnít change any characteristics of the engine running. If I disconnect one injector wire on the driverside it will drop down on idle rpm and run rough. The plugs are brand new TR6 gapped at 28, I get the idea of the ground on the back of the cylinder head but if it works for one side theoretically it should on the other. Iíve also switched coils from one side to the other and injectors, all of this has been the same outcome.


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    Last edited by 03yllwcobra; 01-06-2019 at 07:54 PM.

  10. #8

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    Quote Originally Posted by 03yllwcobra View Post
    The misfire is all the time from idle on. The fuel in the car is E85. Also with the car idling I can disconnect all the injector wires on the passenger side and it doesnít change any characteristics of the engine running. If I disconnect one injector wire on the driverside it will drop down on idle rpm and run rough. The plugs are brand new TR6 gapped at 28, I get the idea of the ground on the back of the cylinder head but if it works for one side theoretically it should on the other. Iíve also switched coils from one side to the other and injectors, all of this has been the same outcome.


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    Can you elaborate on your injector test? Did you unplug the whole bank and it was the same? Or one by one?

    Mike


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  11. #9
    Senior Member Array 03yllwcobra's Avatar
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    One by one until the whole bank was done, if you unplug the driverside one by one is is a noticeable difference in how the engine runs


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  12. #10

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    Quote Originally Posted by 03yllwcobra View Post
    One by one until the whole bank was done, if you unplug the driverside one by one is is a noticeable difference in how the engine runs


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    What efi?

    Do you have the ability to temp header primaries?

    Initially it sounds like you have a common issue across the cylinders. But 1-2 dead holes can seem the same as you progress through some of the common diagnosis. I initially had 2 coils pined opposite on mine and chased it for a minute like you are. I would assume you traced the wiring and you donít have a coil plug swapped. Or harness swapped bank to bank.

    I would verify the coils are firing in order with a timing light. Passenger bank- 1 @ (crank timing 15* for me) [email protected] 285*, [email protected]* [email protected]*. There is a spark event every 90 degrees. And again this is assuming 15* timing for cranking.

    And check for temp in the primaries after running.

    Mike




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    Senior Member Array 03yllwcobra's Avatar
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    Iím using ProEFI, I have a temp gun I could use for temps. I will also re-trace the wiring but I numbered the wires and labeled them all as I slid them through the firewall, unless for some reason the harness from the company is pinned wrong. Also if you rev the car it seems fine but if you try to rev it back to back it will backfire.


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  14. #12

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    Quote Originally Posted by eschaider View Post
    That's a horse of a different color, Nick.

    I presume you have already checked all the ECU and coil grounds so the next likely culprit is reduced electrical power at higher engine speeds. Have you data logged the misfires? If you have and the ECU collected voltage data it would be interesting to see the two plots overlayed.

    Any data logs taken that recorded the misfires can be a treasure trove of how come and why for data.


    Ed

    Nick,

    We had another site member (SVT Troy) who had a shop install his cams for him. The engine 'misfired' when ever he started it and did so at all engine speeds ó just like yours. It turned out the shop had mixed up either the intakes or exhausts for the right and left engine banks. I want to say it was the exhausts but I can't remember anymore. Once the cams were properly installed and phased the engine ran smooth as silk.

    Ford Modmotor cams use a part number format like, YL7E-6A270-AB. The blue numbers (in this example 270) will indicate which bank the cams go on and also whether they are intake or exhaust cams. Intake cams carry the numbers 270 & 271. Exhaust cams cary the numbers 272 & 273. Cams for the driverside of the engine are the odd numbered (271 & 273) cams while the passenger side cams use the even numbers (270 & 272).

    This stuff sounds confusing ó because it is. When you lay it out on paper or on the floor in the garage it becomes much clearer.

    The engine will actually run with (I believe) the exhaust cams swapped side for side. Troy's actually ran without PTV interference (blessedly). Pull your cam covers and check the camshaft part numbers stamped into the cams. You might just discover the same whoops that Troy did and that would instantly explain the funky misfiring.


    Ed


    p.s. Be sure to check both intake and exhaust
    Last edited by eschaider; 01-08-2019 at 12:01 AM. Reason: Added Postscript

  15. #13
    Senior Member Array 03yllwcobra's Avatar
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    Yeah I've got one side off already and the timing cover to check everything but just haven't had time to do it yet. The pistons have fly cuts in them for the valves so hopefully nothing has kissed my pistons yet. I believe the compression test would have yield different results if they had, unless they hit and are stuck shut. Thanks for everyones help and advice, I've got the weekend of so hopefully I get it all sorted out.

    Thanks

    Nick

  16. #14

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    I agree about the lack of PTV interference. Had they hit, your compression would be way down on the wounded holes. That said I still suspect the +/- 30 psi difference bank to bank is attributable to different cam phasing bank to bank. While everything is apart to check which cam is where, this is an excellent time to also check the cam phasing and correct as necessary.

    Although it essentially goes w/o saying, the job of phasing cams with the engine in the car is several orders of magnitude more difficult. While checking phasing is relatively easy, the actual rephasing would be more easily accomplished by pulling the engine. It is noteworthy however, that there are those hale and hearty types who are into self flagellation that have prevailed and done it with the engine in the car, soooo ...


    Ed
    Last edited by eschaider; 01-08-2019 at 05:37 PM. Reason: Spelling and Grammar

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    Senior Member Array 03yllwcobra's Avatar
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    Alright, I went ahead and did a leak down test for the heck of it and all the cylinders were less than 10%. Also when checking everything I noticed none of the timing marks line up from the chains to the gears. Iíve never really degreed cams before but are they supposed to be like that?





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