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BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17469
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2005 Chevy Impala: V..Stalling..all related sensors seem to be working

Customer Question

2005 Chevy Impala 3800 V-6. Stalling problem when warm. I.A.C., M.A.F., T.P.S. and all related sensors seem to be working as they should. All injectors ohm out at 12.5 ohms at 95 degrees eng. temp. Fuel pressure at 52 psi. when engine stalls pressure falls to 0 psi. Replace fuel pressure reg. no help. When the return line is "deadheaded" the pressure holds at 72 psi. Possible pump problem?
Submitted: 8 years ago.
Category: Chevy
Expert:  BOBBYSS replied 8 years ago.
HelloCustomer is the check engine light on in the vehicle? Does the vehicle always start right back up after it stalls?
Customer: replied 8 years ago.
The vehicle orginally came in with the check engine light on, with codes PO350 Ign. coil control circuit, PO507 Idle speed high, & PO1350 Ign. bypass circuit. After doing all of the previous things mentioned, I cleared the codes, and none of those have returned. When cold the vehicle will start and run just fine for about 20 mins. then just shuts off, like someone turning the key off. No misfires or stumbling before stalling out. the engine will then restart but with a low idle about 540 rpm, pick-up and then die. Let the vehicle sit for about 1-2 hours, then it will start and run fine for 20 mins, then the whole visious cycle starts over. The whole residule fuel pressure thing has me puzzled?
Expert:  BOBBYSS replied 8 years ago.
Okay. There is something shutting down the fuel pump. You need to check for power at the pump when the vehicle will not start. If there is power then the pump is the problem. If there is no power then the problem may be in the fuel pump relay or in the ignition switch.
Customer: replied 8 years ago.
The vehicle always starts, it will not stay running at idle, if I hold the rpm at or above 1200 rpm the fuel pressure stays at 51-54 psi. The fuel pressure is always there until the engine stalls then about 2 seconds later it falls to 0 psi. I will check for power at the pump after 20 mins of running when it starts to stall out and let you know what I find of if that was the problem. ThanksCustomer
Expert:  BOBBYSS replied 8 years ago.
Okay. Let me know what you find. If the vehicle does stay running at a higher RPM then you may have a crank sensor that is not reading correctly when it warms up.
Customer: replied 8 years ago.
Sorry I was not able to answer sooner, I have 243 cars in the fleet and limited mechanics because of hunting season.

I probed the fuel pump supply wire and it stays at a steady 13.85 volts until it dies, falls to battery voltage when engine dies, and 5 seconds later to 0.00 volts when the fuel pump relay turns off.

18X and 3X crank sensor signals seem to stay pretty steady on the OTC Genisys, no glitches that I can see. With the previous codes could there possible be a problem with the ignition control module?
Expert:  BOBBYSS replied 8 years ago.
Okay, the fuel pump is not being shut down then. Does the security light happen to start flashing or staying lit when this happens?
Customer: replied 8 years ago.
No Security light, engine just dies, no rhime nor reason!
Expert:  BOBBYSS replied 8 years ago.
Okay. This may be a PCM or ignition control module issue. They may be failing when they get hot. Eventhough your scanner reads okay, I would still lean towards the crank sensor as the most probable issue.
Customer: replied 8 years ago.
I will order a crank sensor and replace, will see what the results are, let you by end of today or early tomorrow. Then I can accept your answer, Thanks
Expert:  BOBBYSS replied 8 years ago.
Let me know what you find.
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Customer: replied 8 years ago.
Sorry it took so long to reply, I was on a leave of absense from work.
I replaced the crank sensor and no change. I took a shot in the dark, seeing the crank and cam run through Ignition Control Module and replaced that. I left work the day before Thanksgiving and the car has not died or faulted out since ICM replacement. You put me on a path I would have not gone down, so I thank you and Accept your help.