stalling in reverse

Discussion in 'General Discussion' started by LaurenMagnum360, Feb 18, 2014.

  1. LaurenMagnum360

    LaurenMagnum360 Senior Member

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    morning guys, so my truck has been stalling in reverse and I'm not really too sure.ohanwts causing it. so I'll break it down to when it happens, and when it doesn't.

    first thing in the morning stalls if put into reverse after starting. but drive works fine.
    same if the truck has been turned off for a bit.

    but if I start it and put it into neutral for a few seconds it's fine then.

    if I start the truck and let it warm up, reverse will not work at all until driven at least a mile. I started my truck this morning and let it warm up. when I got down to the end of my street someone was blocking it, so I put it in reverse and it stalled. I had to hold the throttle to get it started, almost like the engine was flooded. I eventually got it backed up enough after a few tries and full throttle to barely keep the engine running.


    but after I got to work, reverse worked fine.


    I've already replaced the iac, and the transmission shifts perfectly in all forward gears. it almost feels like it's either flooding, or losing spark when it stalls. it's not like it locks up or anything.


    I'm stumped :(
     
  2. Merc225hp

    Merc225hp Senior Member

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    Check the motor over for any vacuum leaks, there are lines the run down the tranny to the top of the xcase they get old and brittle and will leak, next would be to swap out the CKPS. When you replaced the IAC did you clean out the port on the TB where it goes? Did you reset the pcm? Last time a full tune-up was done?
     
  3. LaurenMagnum360

    LaurenMagnum360 Senior Member

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    i'll take a look at the vacuum lines this weekend, along with hopefully getting around to doing the crank sensor.

    i did not clean the iac port, as it was spotless. the iac had just failed and locked up.

    i did not reset the pcm, nor do i know how to do so.

    idk when the last tuneup was. i just put in some new autolite plugs last week, and i'm waiting for this weekend to try and get the distributor cap off. probably will replace the cam sensor while i'm in there.
     
  4. dodge dude94

    dodge dude94 Senior Member

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    You can reset the PCM by removing the positive battery cable and turning the headlight switch on for approximately 15 minutes. Turn it off, reconnect the cable, take it for a drive.
     
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  5. LaurenMagnum360

    LaurenMagnum360 Senior Member

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    i believe i have found my problem.

    i believe my issue is the Map sensor. and i have a hypothesis as to why.

    i plugged my code reader in, and ran live data.

    at idle, i'm drawing 10.2 in/hg of vacuum.... and i have no vacuum leaks.

    my hypothesis is, that since the ECU thinks it is getting 10 in/hg of vacuum, it thinks the engine is under load and is dumping extra fuel into the motor. When i stick it in reverse, the rpms drop more than drive, and the IAC has to compensate even more, resulting in the vacuum level dropping and the ecu compensating for more fuel.

    but, the engine is dumping more fuel, without the T/B opening, meaning it will flood out. which would answer the reason i need to hold the throttle open to get it to start again.

    i just ordered a new map sensor, and i'm hoping it fixes this issue.


    btw, i tested my theory by letting my engine cool completly and I unplugged the map sensor. i started the truck, and it popped the CEL for the MAP not being plugged in.... put it in reverse.... viola... no stalling -_-

    now we'll know for sure in a few days when i get my new sensor.
     
  6. Merc225hp

    Merc225hp Senior Member

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    If you look under the map there is a little rubber hose with a 90 in it that goes to the TB, make sure it's still in one piece and not split all to heck.

    Good find by the way :)
     
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  7. LaurenMagnum360

    LaurenMagnum360 Senior Member

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    i'll take a look at that after work tomorrow when it's still a bit light out.
     
  8. dodge dude94

    dodge dude94 Senior Member

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    ^This.
    Check that hose before you replace the MAP sensor.
     

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