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Car Stalling, jerking and sudden death

Hi, my 2005/2006 Ford focus hatchback car developed a stalling, jerking and sudden stop problem after installation of a catalytic converter and for 5months running. I have changed the spark plugs, ignition coil, fuel relay, used 9fuel pumps, changed slow jet, changed air collector, used 2 fuel pump casings, inner & outer fuel filters and changed the brain box all to no avail. I have also washed my fuel tank from clogs. Diagnosis displayed error codes PO230, P1100 & P720. Please, what could be the possible element that reduces voltage to the pump thereby overheating it 20-30minutes after working or when the A/C is turned on?

I took voltage readings for the battery, relay, inertia switch, alternator and fuel pump. When engine is idle, battery-12.48v & cranking-13.5v. When engine is idle, alternator-12.49v & cranking-13.77v. When engine is cranking, Inertia feed cable before switch-12.92v & after switch-12.84v. When engine is cranking, fuel pump-12.6v & during the stalling, jerking & sudden dead situation- fuel pump-11.6v. The problem is intermittent. it occurs at odd times. Sometimes 20times in a day, sometimes twice, 3times, 40times, but it sure occurs. One cannot predict especially when the A/C is turned on. What are your thoughts on this please?

The P0230 code and the P1100 are where I would look into in that order. Both of these can easily cause your engine running symptoms. The P0720 is a an output shaft speed sensor… responsible for your speedometer and also used for transmission shifting characteristics so this code will not be related to engine running/stalling.

P0230 FORD - The ECM Has Detected A Fault In The Fuel Pump Circuit… The code will be set if an incorrect voltage on the control circuit of the fuel pump relay is detected by the ECM. The fuel pump relay wouldn’t be responsible for the power supply to the fuel pump circuit itself the relay is between the inertia switch and the pump. So the Inertia safety switch is responsible for the circuit power supply. Power for your fuel pump flows directly through this switch… so if it is faulty it may be messing with the fuel pump circuit power supply.

The P1100 points to the MAF and can also cause running problems and stalling…but I would try to suss out that P0230 first. I would be suspicious of that inertia switch. I have found they are either good or totally failed… I haven’t seen a voltage fluctuation with them but it is not out of the realm of possibility as power for your pump flows directly through this device. You could bypass this switch for TEST purposes ONLY. See if the problem goes away…but this should only be for test purpose. That’s what I would do if I didn’t have a new switch handy and or a good diagnostic computer to interface with your engine ecu. See what you get.

The P1100 is also very important for running/fueling the engine. But again, I would try to prove out the inertia switch/fuel pump voltage fluctuation first and then move to the MAF sensor.

For the P1100 you could start the engine and then unplug the MAF…most times the engine should stall and light the engine light. So this is a rudimentary test to see if the MAF is functioning at least at some level…it does not prove it out to be good however…you need a computer to properly see this. The MAF often gets dirty and they sell products to clean them…you can use brake cleaner or carb spray or MAF spray to attempt to clean it.

But with that P0230 pointing directly to fuel pump voltage…You need to suss that out first in my opinion and suspect number one would be the inertia switch. Which could be fluctuating voltage as you drive and transmit road vibrations to the internals of that inertia switch. Measuring voltage when parked isnt the same thing as what could be happening when in motion.


I have no idea if you’re correct @Honda_Blackbird, but this was a great answer anyway. Clear and understandable, but also it seems logically right.

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Please explain. The battery should measure less when the engine is being cranked (“cranking” corresponds to that rr rrr rrr sound when the key is in start) than when idling.

Your posting’s wording is ambiguous, but suggests there may be problem with the battery or alternator or other issue w/the electrical system. Here’s the test your need to do: the battery should measure about 12.6 volts before the first start of the day, cold engine. Immediately after starting the engine, at idle, it should measure 13.5 to 15.5 volts. What are your measurements?

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In my experience, if you unplug the MAF sensor, the engine doesn’t stall. It will actually run better with it unplugged if the MAF sensor is bad. My experience is GM only, Ford May be completely different and stall if the MAF is unplugged. Just curious. Good advice.

Interesting. I guess when the engine is warmed up and the O2 sensors are working the computer can figure out the correct air/fuel mixture without the MAF sensor input. The only difficulty would be when the throttle is moving, but the computer still has the throttle position sensor for that. A cold engine with no valid O2 sensor input &also lacking an MAF sensor input might not do quite as good. @Scrapyard_John … next time you could try that same experiment w/a cold engine.

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I don’t want to sound like I’m making a blanket statement that an engine with the MAF unplugged won’t stall cold or that certain makes won’t stall (although I’d assume they basically all work the same), because I do not know. Was meant as more of a question than a statement.

I have unplugged the MAF on my mom’s Buick (2004ish) to diagnose a bad MAF, and the engine ran fine. She actually drove it home unplugged because it would stall when plugged back in. I drove a 2008 Sierra that I owned with the MAF unplugged for a bit. I was hoping the MAF was the cause of the pinging under load that truck experienced, but it was not the issue. The truck ran fine, though. The check engine light didn’t even come on until I turned the engine off and started it a second time. I assume the pcm just assumes a predetermined value if it doesn’t recieve a signal from the MAF? I have found this to be the case, I think, for several sensors (02 sensor, coolant temp sensor).

I will try that out. Thanks