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stalling on deceleration or when coming to a stop

exmechexmech Posts: 4
edited March 2014 in Pontiac
can someone please help me! I have a 99 bonnie
with 97k. here's a bit of history since i've own this car. the firth month the can run great! when about once a week the car would stall sitting at a red light and i notice that it got harder to start.(about 1-2 sec. holding the key in the start postion). took it to the shop, they had it all day and said it would cost about 800 dollars and that was only for a tune-up and a coil pack. i was like WOW you are kinding, rite?!? so i stoped at the parts store on the way home and bought plugs, wires, gas and air filters, about 80 bucks.
after removeing the fuel filter i notice a rust color goo in it! thats it i said to me self a dirty fuel filter! the car started rite up! not the 1-2 sec start, and ran great again for a week or two. i replaced the fuel filter again, it had a little less goo this time. once again the car ran better (not great)this time. now it doesn't matter if it's a new filter or not it keeps stalling.
i have checked all the vac.lines using carb spray and found no leaks. also cleaned the EGR, pvc and the IACV(idle air control valve). once again this seemed to do the trick! but again the stalling returned!
now the car stalls at least 10 times on the way to work and 10 times on the way home.
but now the check engine lightcomes on when the car stalls, the code is P0172 and that sulphur smell coming out of the exhaust. at a light the RPM gauge will start at 800 and steady and then jump up to 1500 down to 500 back up to 1000 then to zero and stall. some times the car's computer will try to fix this proplem(i think) and over do it causeing the car to jump forward slamming the trans into gear hard like.
this stalling thing is VERY dangerious for me and i'am a guy just think if a woman or elderly person were driveing it when it stalls and have no power steering!
please help me track down this hugh problem.


  • alcanalcan Posts: 2,550
    Start by pulling the vacuum hose off the fuel pressure regulator and checking for the presence of gas in the hose. If so, replace the regulator.
  • fantascpfantascp Posts: 175
    Gary- I had a similar problem on a 91 Buick skylark I used to own-The car would shake when I started to de-cellerate coming to a red light or when trying to go thru a toll plaza to pay the toll was an adventure. The car would stall out, then start up in again, but the minute I put it in gear- stall again- trans would bang etc. the problem was with the transmission- its a transmission lock-up plug located on the side of the trans- it controls the gears etc. - when it goes bad it fools the trans and computer into thinking its shutting down etc- Ask your local mechanic to Check out this plug &
    1. disconnect this plug(Takes all of 5 seconds!)- you'll end up getting about 3/5 mpg less per tankful or
    2. take it to a Dealership to replace the unit- it ran me around $300 to $400.00 to get it fixed the first time- it did it again a few years later and i just had my mechanic disconnect the lock up plug -no more problem.
    Good Luck,

  • fantascpfantascp Posts: 175
    The actual unit that I had replaced is called THE TRANSMISSION CONTROL MODULE.
    It allows the TCM to shift the Trans and turn the LOCKUP on or off.
    The plug i'm referring to is connected to this unit. Disconnecting this plug should correct your problem.
  • exmechexmech Posts: 4
    thanks this really helps
    the first thing I did was pull the vacuum lead off the fuel pressure regulator, guess what, fuel was dripping from it and when I left the car running and vacuum line off gas was spitting from the FPR!! so off I go to the parts store and I will post my results when finished! thanks alcan!
      the TCM Y will keep that in mind if the FPR doesn't do the trick. but i'am thinking thats not my problem this time. i had a buick years ago that had that kind of problem but it only stalled when in gear.... my car will stall in park or in neutral. thanks for your input, I have seen wierder things!
  • alcanalcan Posts: 2,550
    Keep us posted on the results. Btw, the component responsible for the engine stall when coming to a stop is the torque converter clutch solenoid, not a control module. When the converter clutch is engaged, it provides a mechanical link between the engine's crankshaft and transaxle input shaft, eliminating converter slip and increasing fuel economy 3-4 mpg. Very common on GM fwd 3 speed transaxles (occasionally affects overdrive models) for the solenoid to become contaminated with ferrous wear particles and bind in the applied position. The clutch can't release, and the net result is the same as stopping a manual transmission vehicle without depressing the clutch pedal.
  • fantascpfantascp Posts: 175
    Sorry Gary- Alcan is right- the part is the TCC
    not the TCM.- My Mistake.
  • exmechexmech Posts: 4
    thanks alcan!!
    think that did the trick!!!
    5 mechanic overlooked and had no idea what the problem was, one of them was from the dealership! why is this, are mechanic not trained today the way they were years ago???
    i'am just glad i found someone that is a MASTER of their trade!!!
    i will post again in a week just some others that may read this know that the fuel pressure regulator can and will cause this kind of stalling problem on GM cars.
  • alcanalcan Posts: 2,550
    You provided the key by posting the P0172 diagnostic trouble code (Fuel trim too rich, Bank 1). Glad to hear it worked out for you.
  • My stalling problem is as follows. The engine dies sometimes when you are driving along and press the automatic window switch on the drivers side door to put the windows up or down. Now, the engine does not stall every time you do this. At times it stalls while waiting at a red light or just driving along. I can drive for a week and every thing is fine. Other times it stalls after driving 10 to 50 miles. The car has been at the Pontiac garage for 10 days and they can't figure it out. After an hour or so, the engine starts right up and runs fine.HELP.
  • exmechexmech Posts: 4
    ALCAN fixed my problem with flying colors i may add!! its been a week now and no sign of stalling any where!! cheap fix for only 85 dollars for the part and 12 dollars for snap ring pliers and 10 min. of my time!

    easesame please read the later post by alcan
    sorry that i can't help you,any more then that.
  • alcanalcan Posts: 2,550
    That one's a puzzler. Sounds almost as if the window's operaton is putting a high load on the vehicle's electrical system. First things I'd check would be all alternator wiring harness connections, battery cable connections (both ends), engine grounds, and the harness between the LF door and A pillar.
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