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90 2500 stalls ??

Discussion in 'Chevy Trucks' started by 66Construction, Apr 1, 2003.

  1. 66Construction

    66Construction Senior Member
    Messages: 315

    I cant for the life of me figure out whats wrong with this truck. It's a 5.7 TBI. It starts fine idles ok but dies in drive or reverse with your foot on the brake. It goes great but stalls at almost every red light. I had it out in the mud last week pedal to the deck mud flying no problem, stop with it in drive and it dies. It's been running rough and stumling for a while and getting worse, this was all hapening before the run throught the mud also.

    The distributer and module are new, the coil is new the cap and rotor are new the plugs and wires are new, the pcv valve is good the fuel filter is new the egr valve is new along with the selenoid. Pulled the map sensor and replaced with one we had at the shop same thing, disconected it all together same thing. disconected the tps (which is only a couple years old) same thing. Timing chain is fine. No trouble codes in the computer, computer seems to function ok, the check ehgine light came on when we disconected the sensors.

    I'd appreciate any suggestions, at this point, my mechanic was even scratching his head over it

    Thanks Casey
     
  2. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    This may sound stupid, but check the connection on the trans for the lock up converter. I just read about a similar problem with a GM car, and it turned out to be a bad connection at the TC lock up wiring connection.

    ~Chuck
     
  3. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    I suspect the IAC motor.It is on the throttle body ,it has a 4 wire connector on it,and a 1 1/4" or bigger wrench to get it off. At the minimum pull the IAC motor,clean the carbon,and the seat it sits in,and try it again.I've had a lot of those go bad at real high mileage.
     
  4. Mike 97 SS

    Mike 97 SS Banned
    from U.S.A.
    Messages: 1,106

    Sounds to me like converter lockup. Try disconnecting it and see if it still stalls when you put it in gear. Im pretty sure it will have a plug that you can easily unplug just to try, the same plug that Chuckie boy is referring to. :D Mike
     
  5. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Unless the check ball is stuck in the plastic lockup sleeve,lockup will not be on . There are electrical switches in the trans to keep it out of lockup,in 1st and reverse. if you just pull of the electrical connector on the trans the truck should run fine,you will just not have any lockup or cruise control. A locked TC will make the trans shift very harsh and abrupt both up and down,and it will lug to a stall as you stop like a standard would if you stopped without puishing in the clutch. What is the idle speed,both Hot and cold?
     
  6. 66Construction

    66Construction Senior Member
    Messages: 315

    Sorry I didn't check this yesterday, I fell through a stair opening in a house we're framing and it ruined my day.

    Anyway.....My mechanice checked all the connections at the transmission etc, he had also just put a new tranny in it. In frustration we knocked the freeze out plug off the throtle body and turned up the idle a 1/4 turn and it's improved a lot. It only stalls at realy long red lights.

    John I didn't even know what an IAC motor was. I'll get with my mechanic tomorrow and check it out. I'll let you guys know what happens. Thanks for the help.
    Casey
     
  7. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Casey,the IAC motor is what controls the idle speed. It allows air around the throttle plate,it is supposed to conmtrol idle speed,fast idle and keep the actual RPM within 25 RPm of the deisired RPM. You may get a check engine light with the throttle opened 1/4 turn. But only if the idle gets too high. I think the IAC motor is bad form what ive read. You need to get a scanner on that truck,and a good mechanic will knwo if its working by the the counts the IAC is at,and the desired idle,/actual idle speed. The IAC driver is the ECM,that could be bad also.The IAC is much more common. Casey if you have nextel,pm me,ill walk yout hru testing the IAC motor.
     
  8. Mike 97 SS

    Mike 97 SS Banned
    from U.S.A.
    Messages: 1,106

    That John is one hell of a guy! :drinkup: Mike :)
     
  9. JohnnyU

    JohnnyU 2000 Club Member
    Messages: 2,040

    Casey-

    I think John is correct about the IAC, however it may be that the valve cannot seat, or that it is junked up. My 91 was doing something very similar, I had to hold the gas and brake at about 1000rpms at stoplights to keep it running smoothly. I had replaced the IAC just two years ago, so I did not suspect that. I removed it, and found that the passages inthe throttle body itself were coated in a varnish-like crap layer. After spraying it with Tb and Carb cleaner and a few q-tips it seems to run much smoother.

    There is still some fluctuation, like a slight cam, not like the drag racing cam that was in there last weekend lol. I will probably buy a rebuilt kit for the throttle body this spring or summer sometime to see if i can completely solve the problem. Good luck!

    -John
     
  10. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    John ,in my first post I said to remove the valve,and clean the carbon,and seat and try it again. Carbon can and does plug the passage,and creates a low idle/stall or a high idle condition.
     
  11. JohnnyU

    JohnnyU 2000 Club Member
    Messages: 2,040

    oops, I didn't see that until right after I clicked the post button.


    Is there any way to prevent this from happening?
     
  12. wyldman

    wyldman Member
    Messages: 3,265

    You can prevent,and sometimes fix this problem by cleaning the IAC passage and throttle body every once and awhile.Go to your local Ford dealer and buy a can of Tune-Up Cleaner.Get the truck hot,and spray the entire can slowly into the throttle body,and IAC passage.Just as the can runs out,shut the truck off,and let it sit for 30 mins.Fire it up and drive the snot out of it.It will run much better.It also helps clean up the upper intake,and the backside of the intake valves.They have some product for cleaning throttle bodies,but the Ford stuff is by far the best.It's also great for degreasing engine parts too.
     
  13. 66Construction

    66Construction Senior Member
    Messages: 315

    I found the IAC my mechanic knew what/where it was. I plan to clean it tonight or saturday morning whenever this freezing rain stops. I'll post what happens after I clean it out. Turning up the idle was definitly only a temporary fix I can see that already.

    Thanks John , I do have nextel...I'll get in touch via an e-mail if cleaning doesnt help it. I don't know if we have a scanner for that truck, just the piece of junk that grounds the diagnostic terminal. I can probably get my hands on one.

    This isn't the first time I've posted problmes with trucks and John has known the answer...He is quite a guy. John I'll have to buy you a beer sometime.

    Thanks Casey
     
  14. 66Construction

    66Construction Senior Member
    Messages: 315

    After the snow/sleet/ freezing rain I finnaly got my head back under the hood of this truck. Wyldman thanks for the tip on the ford cleaner The throtle body looks like new. After cleaning the IAC the truck idles pretty nice now. No more stalling at all. I will probably just replace it when I get a chance but for now it runs just fine.

    Thanks to everyone for the help!
    Casey
     
  15. wyldman

    wyldman Member
    Messages: 3,265

    Good to hear it's fixed. :drinkup:

    That Ford stuff is awesome for carbs and throttle bodies.