2010 1500 4.7 won’t start when engine is cold

[dougmillard77]

My truck wouldn’t quite start one day back in September, it would almost start, was getting fuel, had a good spark and we thought it was either the cam or crank sensors, they both tested good but was told it could be a intermittent issue with either one and that’s why it attempted to start, so I replaced both and still wouldn’t start, thought maybe it was flooded as I sprayed fuel into the tb earlier, so I held the pedal to the floor and fired up. The weather warmed up and it started good until one cool morning it did the same thing, held it to the floor and fired right up. It was flooding on cold starts all along, starts great when the engine temp is warm, but when it cools down to a certain temp it’s pedal to the floor to start! If I plug the block heater in it will start after 1/2 - 1 hr no problem! Only 2 codes have come up PO172, PO175 if I don’t hold the pedal all the way to the floor or do it quick enough, and never get a code when plugged in or if eng is still warm! I am thinking possibly the eng coolant temp sensor as I flushed the cooling system about a week before this started and I know that shouldn’t cause the sensor to go bad! Any help would be greatly appreciated as I don’t want to replace another sensor unnecessarily!

 

[Rampant]

My truck wouldn’t quite start one day back in September, it would almost start, was getting fuel, had a good spark and we thought it was either the cam or crank sensors, they both tested good but was told it could be a intermittent issue with either one and that’s why it attempted to start, so I replaced both and still wouldn’t start, thought maybe it was flooded as I sprayed fuel into the tb earlier, so I held the pedal to the floor and fired up. The weather warmed up and it started good until one cool morning it did the same thing, held it to the floor and fired right up. It was flooding on cold starts all along, starts great when the engine temp is warm, but when it cools down to a certain temp it’s pedal to the floor to start! If I plug the block heater in it will start after 1/2 - 1 hr no problem! Only 2 codes have come up PO172, PO175 if I don’t hold the pedal all the way to the floor or do it quick enough, and never get a code when plugged in or if eng is still warm! I am thinking possibly the eng coolant temp sensor as I flushed the cooling system about a week before this started and I know that shouldn’t cause the sensor to go bad! Any help would be greatly appreciated as I don’t want to replace another sensor unnecessarily!

Unfortunately, you'll need a scan tool that can instigate self-tests to do most of the checks involved with these codes. I figure if you had one, you wouldn't be asking for help here. Nonetheless, here is some info to help you better understand what may be happening. I wish I could help you more, but you're going to need a decent scan tool to see what's actually happening in there to pinpoint the culprit without just changing parts.

From Alldata:

P0172-FUEL SYSTEM 1/1 RICH
P0175-FUEL SYSTEM 2/1 RICH

Theory of Operation

The intent of this diagnostic is to identify rich or lean fuel system abnormalities which would cause vehicle emissions to exceed 1.5 times any of the standards. The base fuel feedback control will maintain the desired fuel/air mixture by modifying the injected fuel quantity according to the oxygen content of the exhaust gas. The Powertrain Control Module (PCM) makes short term and long term fuel corrections based on feedback from the Upstream O2 Sensors. The PCM monitors feedback from the Downstream O2 Sensors to determine and optimize the efficiency of the Catalytic Converters.

The Upstream Fuel System Monitor and Downstream Fuel Trim Diagnostic monitors operate very differently;

- Upstream Fuel System Monitor

- The Upstream Fuel System Monitor diagnostic monitors the Upstream O2 Sensor feedback to determine the actual fuel/air ratio, which is then compared to the desired fuel/air ratio. The error between the two is measured and corrected for. This correction happens "live" and the instantaneous value of the correction is stored in short term fuel trim. Short term fuel trim is intended to correct temporary or dynamic errors in the air/fuel ratio. If the value of short term fuel trim is large enough for a sufficient period of time, it is assumed that whatever is causing the error is permanent and not temporary and the value in short term fuel trim is moved to long term fuel trim. When this transfer occurs, the short term fuel trim is re-zeroed and continues to look for temporary errors. If the combined value of the total fuel correction stored in short term and long term fuel trim (rich or lean) exceeds a calibrated threshold, for a calibrated period of time, a fuel system monitor fault is recorded.

- Downstream Fuel Trim Diagnostic

- A Downstream O2 Sensor goal voltage is selected to maintain the optimum catalyst efficiency. Corresponding Upstream O2 Sensor rich/lean switching point thresholds for various operating conditions are also selected which normally result in a Downstream O2 Sensor voltage close to this goal voltage. During normal operation, whenever the upstream rich/lean switching point threshold does not result in the desired downstream goal voltage, the downstream fuel trim feature "trims" (adjusts) the upstream rich/lean switching point threshold up or down appropriately until the desired downstream goal voltage is achieved. The amount of trim adjustment that is added or removed is called "downstream fuel trim." If the trim adjustment to the Upstream O2 Sensor goes beyond a calibrated threshold (rich or lean), a fault is set.

When Monitored and Set Conditions

When Monitored: This diagnostic runs continuously when the following conditions are met:

- With the engine running in closed loop fuel control.

- Battery voltage above 11.0 volts.

- Barometric pressure greater than 75 kPa.

- The ambient temperature above -7°C (20°F).

- Fuel level greater than 12%.

- Altitude below 2590.8 m (8500 ft.).

Set Conditions:

- When the sum of the short term and long term fuel corrections is less than a calibrated threshold, generally 67% (100% is nominal), the fail timer will increment. After 30 seconds of fail time the diagnostic fails.

Default Actions:

- The MIL light will illuminate.

- If the vehicle is equipped with the stop/start feature, the system will be disabled when this DTC is active.

 

[Ratket]

My 2010 Ford F-150 with the 3.7v6 did this same damn thing, it only did it for two winters though then it stopped and has been fine since. It then started to do the same thing in the summer and I noticed a fuse for like the starter relay or something wasn’t seated fully” fuse box above radiator and shakes like mad when driving” so I reseated it and got a spare fuse from ford. Been fine ever since. But it was the damnest thing when
It did it during the winter, I had to give it just the right amount of pedal to get it to start, none of my coworkers would use my
Truck cause they couldn’t get it started if it sat for to long. Even had ford take a stab at it and they just threw parts at it and I remember it still did it after I got it back. But since I could get it started it made me think it was a temperature sensor of some kind. Like it thought it was warmer or colder out than it was. good luck, keep us posted.

 

[Dodge4x4810]

When it does start, does it seem like it has full power? How many miles are on it? Like said earlier, it is much easier if you have access to a scan to where you can scan all your monitors. Those rich codes and it starting hard cold could be many things. But if it has a lot of miles on it, it is a good possibility that the cats are starting to collapse or your egr is stuck wide open. How does it idle and run after it starts? If you have a vacuum gauge you can test to see if the cats are getting clogged easily, or pull your upstream o2s. The egr you can try unplugging, but that does not always work if it is mechanically stuck open.

 

[broken arrow]

so what was cause ?

 

[EdGs]

Alien abduction.