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Thread: 93 Mighty Max Low Power

  1. #1

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    93 Mighty Max Low Power

    I have a 93 Mighty Max 2.4l that had 300,000 miles on it. I just rebuilt due too a cracked head and thrown rod. So replaced the Head and Crankshaft. I sent the engine in to be cleaned a preped. I also replaced the pistons, O2 sensor, coolant temp sensor, plugs, oil pump, fuel pump and filter. So after god knows how many headaches the truck is running again. Although now its smoking and getting low power. I'm sure its running too rich as I'm getting unburned carbon out the pipe. The check engine light is on so I pulled the codes. I'm getting a 21 (Coolant temp sensor) but only after a bit of driving. And a 42 (Fuel pump system) and that one come up as soon as you start it after clearing the codes. I'm pretty sure the Timming belt is on correctly but not so sure the Dis timing is set right. My dad adjusted it for me but forgot to ground the ECU pin. Not sure if that could make it run so rich. Any help or ideas would be greatly appreciated as my dad is a retired mechanic but I'm just a lowly PC tech so very little experience with such issues. Also if someone could point me in the right direction for this manual section I keep hearing about.

  2. #2

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    A bad coolant temp sensor, can cause the truck to run rich

  3. #3


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    Advanced timing can make it run rich, emissions of high CO and run hot, also float level, high fuel prsesure can too.

  4. #4



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  5. #5

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    Well I adjusted the timing last night and it seems to be running much better. It wasn't even close. When I installed the timing belt I did match up with the correct mark on the head. I drove it home on the interstate last night and checked the codes again. I'm still getting the code 42 which is driving me nuts since I changed the fuel pump, strainer and filter. Any ideas of what else could be causing the code 42.

  6. #6

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    Ok so I played with it some more last night and the timing is now dead on. I seem to have much better power and I'm not getting smoke anymore. Although I'm still having the code 42 for the fuel system. I also notice that it seems sluggish to respond sometimes like it's having trouble getting gas quickly enough. As I stated before I have already changed the Fuel pump strainer and filter. So I'm guessing I might have a clogged fuel line or an issue with the fuel pressure regulator. Is there any good way to troubleshoot this issue further? I'd hate to spend 80$ or so on a fuel pressure regulator that I don't need.

  7. #7



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    I would say fuel press. Reg or maybe gas cap? Or evap return line, check the manual for troubleshooting the code
    Josh
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    You would need to put a pressure gage on the fuel rail and check pressure wile driving. Thats the only way to check the regulator.
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  9. #9

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    there isn't a test port on the fuel rail on these trucks, I used an adapter that fits in between the fuel hose and the fuel line by the fire wall

  10. #10

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    can you let me know what adapter you used. I rented a fuel pressure tester but can't hook it in. I tried finding a adapter that would work but haven't had any luck yet.

  11. #11

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    The adapter i used came with the fuel injection machine i used. where did you rent the fuel pressure tester from

  12. #12

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    It came from autozone. But we didn't see anyway to connect it to the fuel rail.

  13. #13

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    Did you get this sorted out

  14. #14

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    Quote Originally Posted by Rahtid View Post
    Did you get this sorted out
    Actually no I haven't touched it since. I've had another issue crop up. I can no longer shift into gear. It seems where the linkage goes to the transmission something is messed up. Everything up to the transmission looks fine but unfortunately I can't get to where it actually connects since it's on the topside of the transmission. If anyone knows what part that may be and if I'm going to have to drop the transmission to replace it. It seems like the metal the linkage connects to is bending instead of moving like it should.

    I still would love to know if someone can give me a part # for a fuel pressure tester that will work for this truck so once I get the transmission shifting properly I can try and hunt down that issue.

    Thanks to everyone for the help and advice up to this point.

  15. #15

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  16. #16



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    The shifter probably came out of the slot, because of the bushing. Pull the shift boot off, and there are three bolts To pull the shift ass. Off and take a look
    Josh
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  17. #17

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    Quote Originally Posted by Rahtid View Post
    This appears to be a part for a manula transmission. Mine's an automatic. And I traced from the shifter to the transmission. Those linkages are moving correctly but where it reaches the transmission there seems to be an issue although I can't see it since it seems I would have to drop the transmission to get to it. I thought about cutting an access in the floor but didn't know if I would still have to drop the transmisson

  18. #18



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    Sorry thought you had a manual tranny. Make sure your kickdown cable coming off the carb is adjusted correctly or it won't shift right. There's manuals somewhere on the board
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  19. #19



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    The fuel pressure need to be checked before or after the fuel regulator? or does it matter. I would think after the regulator.
    Anyway...here is your entire fuel system.

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  20. #20

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    Quote Originally Posted by DroppedMitsu View Post
    Sorry thought you had a manual tranny. Make sure your kickdown cable coming off the carb is adjusted correctly or it won't shift right. There's manuals somewhere on the board
    All good. I already adjusted the downshift cable awhile back everything was going decent until this. what really sucks is I had it parked on rocks when it decided it didn't want to shift out of park. Wish I would have left it in the driveway as now I can't even push it anywhere.

  21. #21



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    Do you feel it clicking through the gears? It could be a loose shifter linkage bolt at the trans.
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  22. #22

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    Quote Originally Posted by camoit View Post
    Do you feel it clicking through the gears? It could be a loose shifter linkage bolt at the trans.
    Yea it's not shifting through anything. but when we disconnected the linkage right before the trans and tried moving it by hand it just felt like a piece of metal was bending instead of moving. I wish the linkage was on the side instead of the top where you can't really get to it.

  23. #23



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    If you jack up one wheel and release the brakes to remove any bind from the drive train, does the same thing happen?
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  24. #24

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    Quote Originally Posted by camoit View Post
    If you jack up one wheel and release the brakes to remove any bind from the drive train, does the same thing happen?
    You know I'm not sure. I'm assuming you mean one of the rear wheels. I have the front jacked up which was apain in the A$$ since its on rocks currently. I'm going to a concert tonight so if I don't try this today I'll have to try it tomorrow.

  25. #25

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    Well I finally got to looking at it a bit more and where the linkage connects to the transmission is definitly just bending. So I'm thinking it's like I've read where maybe the truck moved a little after putting it in park so the transmision can't shift due to pressure. But in this case the metal must have been week and therefore just bends now. Problem is I can't seem to find out the part I need to order. Is there a good transmission diagram out there that may help me hunt down the part?

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