Ford V10 6.8L cold start issue
- Thread starter pacem
- Start date
The engine has 52K miles on it. It runs very well and feels strong. No smoke and no issues operating.
I an run key-on-engine-on test inside of Forscan.
could it be just the throttle body needs to be cleaned?
How many coolant temp sensors does it have? Have you checked the measured value readings to confirm they are correct?
It does not have a single coolant temp sensor, there temp sensor that is screwed into the head but there isn't one touching the coolant.
What is it about it that makes it start when it's warm (within 2 hours) and much harder when it's cold overnight? Nothing else changes but temperature. I will get the fuel pressure readings but this has to be a major clue.
What is it about it that makes it start when it's warm (within 2 hours) and much harder when it's cold overnight? Nothing else changes but temperature. I will get the fuel pressure readings but this has to be a major clue.
Right, so it’s an engine temp sensor though. Does it give a correct reading?
Yeah, all the sensors have correct readings based on Forscan. It passes the Key-on-engine-off test and the engine-on test.
Started today after 8 seconds of cranking and some light gas pedal. I shouldn't have to do that in a fuel injection vehicle.
So not clear what the malfunction that's still there. Clean the throttle body? I have been running it a lot with fuel injection cleaner. Why does it need the gas pedal to be engaged to start? It doesn't look like it can start without light throttle and has always been like that for the last 2 years.
Today the idle was a bit weird, steady, but when I hit the gas, I could not rev it up to 3,000 rpm, it barely made it 2,000 and the tach wanted to drop. I remember a week ago when I was able to start it for the first time in months, it would readily rev to 3,000 if I wanted to.
The first thing it does when the throttle is hit, the rpms drop a bit, then go up. Maybe it's the gas? Maybe I put too much fuel injection cleaner? I got the gas yesterday in a container and poured it in.
all in all it does much better after the crank pos sensor swap (which BTW was never flashed as having an error, the mechanic I got swapped it after a hunch). Nothing in Forscan, his Ford scanner or my scanner. But still, the perpetual problem of "Easy start when hot, difficult start after sitting overnight". Is it a Ford V10 thing? An undocumented feature?
Started today after 8 seconds of cranking and some light gas pedal. I shouldn't have to do that in a fuel injection vehicle.
So not clear what the malfunction that's still there. Clean the throttle body? I have been running it a lot with fuel injection cleaner. Why does it need the gas pedal to be engaged to start? It doesn't look like it can start without light throttle and has always been like that for the last 2 years.
Today the idle was a bit weird, steady, but when I hit the gas, I could not rev it up to 3,000 rpm, it barely made it 2,000 and the tach wanted to drop. I remember a week ago when I was able to start it for the first time in months, it would readily rev to 3,000 if I wanted to.
The first thing it does when the throttle is hit, the rpms drop a bit, then go up. Maybe it's the gas? Maybe I put too much fuel injection cleaner? I got the gas yesterday in a container and poured it in.
all in all it does much better after the crank pos sensor swap (which BTW was never flashed as having an error, the mechanic I got swapped it after a hunch). Nothing in Forscan, his Ford scanner or my scanner. But still, the perpetual problem of "Easy start when hot, difficult start after sitting overnight". Is it a Ford V10 thing? An undocumented feature?
The mystery has been resolved, it was the crank position sensor. It started starting, gradually better and better. Today started without hitting any throttle at all. Cranked for 6-8 seconds and then started.
Upon examining the crank pos sensor, some oil was on the connector. Resulting in weak/ intermittent signal.
The **** thing was not picked by any any scanner. It had zero codes on it after I fixed MAF.
Upon examining the crank pos sensor, some oil was on the connector. Resulting in weak/ intermittent signal.
The **** thing was not picked by any any scanner. It had zero codes on it after I fixed MAF.
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- Jun 26, 2023
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Have been following this since you started posting about it, but didn't really have anything different to contribute. Glad you figured it out!
A prime example of it being a great idea to check wiring and connections before replacing parts, though it is extremely easy to assume a sensor issue and not do so. I believe we've all done it at one point or another!