I've been trying to troubleshoot my truck for awhile and I think I need a second opinion now before I spend any more money. Sorry if this is a long post.

The truck is a 96 F150 with the 4.9l inline 6 and 5 speed manual. It's a shortbed with dual gas tanks as well.

Anyway, I've been having hard starts both with the engine cold and after it's warmed up. I also tend to get misfires for a few minutes on cold start but I can let the truck idle and it will eventually go away. The only CEL I have is for the misfires. I did have related to emissions, but it went away after I had the battery unplugged for a bit and has never come back.

Here's what I've replaced so far:

Replaced both o2 sensors
new EGR
new PCV
new distributor cap and rotor
new coil
plugs and wires were changed a few months ago when I bought the truck. Double checked them and they are fine

I put a fuel pressure gauge on it and I was only getting around 40psi with the engine running, which seems a bit low from what I've been able to find. I tried pulling the vacuum line off the fuel pressure regulator and there was no change to the way the truck idled or the fuel pressure my gauge was reading.

I'm probably going to go ahead and change the fuel filter this weekend, but do you guys the fuel pressure regulator could be bad? I don't want to just start throwing money at my truck if I can help it and I like trying to do as much work myself as I can.

*edit*

oh and I just remembered I found out that the coolant temp sensor doesn't appear to be working. I don't know how much the computer controls on these trucks, but could that be cause some of the issue as well?

 

Did any of the parts you replaced fail a published test? Did you keep any of the originals? Did you buy name-brand replacements (like MotorCraft, Echlin, Standard, BWD, etc.), or cheapos from the zone?

Ford specifies higher pressures for the 4.9L, but mine runs perfectly at V8 pressure (35-45psi). Study these diagrams & their captions:

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The computer controls everything about the way the engine runs, and the ECT is an important sensor, especially if your symptom seems to be related to engine temperature. Are you referring to the all-brass one with a single threaded post on top, or the one with a 2-pin plastic socket? How exactly did you determine that it's not working?

 

Thanks for the reply Steve!

All of the replacement parts were name brand. I've had too many issues with house brand parts. The truck has 183k miles and since I don't know much about the previous service history I just started replacing some of the cheaper components that have a tendency to go bad or get neglected.

Cool, good info and those diagrams help a ton! Will definitely give me some stuff to go over here at work.


I'm assuming it's the one with the 2 pin socket up near the front of the engine. I guess I should test the sensor first. My coolant temp gauge isn't working and the previous owner said he replaced the sensor once and the gauge worked for a little bit and then died again. I don't know if he bought a cheap sensor or if there's something else wrong. I guess I need to look up how to test it to make sure it really is bad and it's not some other issue.

Looks like I have some work cut out for me this weekend. This is my first Ford. I've always been a GM guy. I love this truck though.

 

Oxygen sensors & EGR rarely go bad, they don't require maintenance (so no possibility of neglect), and aftermarket replacements are RARELY as good as OE (even after 15 years). I hope you kept the originals. Every day, all the time.The gauge doesn't use a "sensor"; it uses a "sender". Sensors are for the computer. Automotive Terms & AbbreviationsRead these:

. Welcome back from the dark side.