Hello,

I have a 1997 f-150 V6 4.2L 2WD. I've been noticing a few symptoms going on and aren't sure if they're related or not. Firstly, I hooked my code reader to the truck and I have P0453 DTC active: Evaporative Emissions Control System Pressure Sensor High Input. As far as symptoms, truck runs overall pretty well. However, if I shut off the truck after running for awhile and then immediate attempt to start it back up, the starter will spin the flywheel but it won't ignite unless I apply pressure to the gas pedal. Again, this is only when it's hot. I hooked up a fuel pressure gauge to the fuel rail and have 35 psi when running, and seeing as how I don't really have any other fuel-related issues going on (aside from the DTC, which I'm unfamiliar with, so it may be related??), so I don't think it's a fuel pump or anything issue. Anyone had this problem before? Maybe an issue with the TPS? I work on diesel trucks so throttle body systems are foreign and strange to me.

Thanks for reading and for this great community,
Dylan

 

Better describe the throttle application.
It is just off idle or more than about 7/8 to wide open throttle allows the motor to start.
It's an important difference to the issue.
Good luck.

 

I'd say 7/8ths to wide open. Usually, when it gets going it idles fine, but today when it happened it actually died shortly after getting it going so I had to repeat the depressing gas pedal to get it started and then sit there revving the engine up for a few seconds to get it going sufficiently as to not let it die. First time that's ever happened. Usually it starts up (with gas pedal depressed) and then works fine.

 

OK, now lets proceed to why.
When you go about 7/8 or more throttle position you shut off fuel injection such that the motor pumps air through the cylinders cleaning the extra gas out to the point the plugs will fire again..
This means the motor is flooded with gas.
The reasons can be the following:
1. Faulty fuel regulator diaphragm allowing gas to flow into the intake manifold through it's vacuum control line.
2. Running fuel pressure to high.
3. One or more fuel injectors are leaking fuel at rest.
4. Thermostat stuck open.
5. Faulty CHT (cylinder head temp sensor) resistance telling the computer the motor is to cold which riches up the fuel injection.
It has to be one of these reasons as there is no other source for 'that much' extra uncontrolled fuel.
Good luck.

 

blue grass you have got to be the smartest man i know when it comes to vehicles.