closed vs open loop

Stewart Way · 06-02-2016, 09:32 PM

Not race related but hopefully someone can answer my question. Have a 2001 Merc Marquis that was a 3rd car just to have incase. About 100,000 miles on it. It developed a problem that 3-4 miles after driving it will start to hesitate and finally die. If you are going 45 you slow to 35 then 25 then it quits. Let it sit a few minutes it starts back up and in a mile or so it dies again. Hooked a fuel gage up and the pressure stays around 46 so I ruled out fuel. No codes that we can find. My son is a mechanic and he has played with it off and on for months. Nothing. I think when it is warmed up and goes from open to closed loop something is getting a bad signal and shuts down. My son thinks there may be a short in the wiring that is supplying a sensor with the 0-5 reference voltage. I don't know enough about the EFI stuff to help.
Question is, short of solving the problem, can the system be fooled somehow to stay in open loop to see if it will stay running past 3-4 miles? Maybe fool the temp sensor if that is what tells the system to got to closed loop. If this can be done would it hurt anything to leave it that way other than mileage?

Thanks

06-02-2016, 09:32 PM	#1
Stewart Way Member Join Date: Aug 2003 Location: Atlanta Posts: 476 Likes: 20 Liked 70 Times in 22 Posts	closed vs open loop Not race related but hopefully someone can answer my question. Have a 2001 Merc Marquis that was a 3rd car just to have incase. About 100,000 miles on it. It developed a problem that 3-4 miles after driving it will start to hesitate and finally die. If you are going 45 you slow to 35 then 25 then it quits. Let it sit a few minutes it starts back up and in a mile or so it dies again. Hooked a fuel gage up and the pressure stays around 46 so I ruled out fuel. No codes that we can find. My son is a mechanic and he has played with it off and on for months. Nothing. I think when it is warmed up and goes from open to closed loop something is getting a bad signal and shuts down. My son thinks there may be a short in the wiring that is supplying a sensor with the 0-5 reference voltage. I don't know enough about the EFI stuff to help. Question is, short of solving the problem, can the system be fooled somehow to stay in open loop to see if it will stay running past 3-4 miles? Maybe fool the temp sensor if that is what tells the system to got to closed loop. If this can be done would it hurt anything to leave it that way other than mileage? Thanks __________________ Stewart Way 2424 SS