Boris Temkin

So my truck has been perfect for the 4 months I've owned it, until a couple weeks ago. It's a 2008 4.6L with 130,000 on it, no mods.

I started it up and had a very rough idle, then it died. Felt like it was starving for fuel so I started it again and gave it a little throttle, it died right away. The truck started like normal after about 20 minutes and I got it home. I drove it again a few days later and it was normal until I shut it off and wanted to start it back up, it did the same thing as before and wouldn't start, even after waiting 20 minutes. The next day, it started right up and I drove it home.

I read some of the forums and signs all pointed to the FPDM, so I got a new one (a Dorman) and installed it. Changed the oil/filter too. It started right up and I had it idle for 10 minutes, no problems. Just drove it and it was perfect, had a very strong idle and drove like new. Then, cut it off and wanted to start it again and it did the rough idle for a few seconds then died. Wouldn't start normal after 20 minutes either.

So any ideas would be great.

I should add that I never abuse it, it was perfect for the first few months I had it, a few weeks ago we had a ton of rain and I drove through some deep puddles. I also ran out of gas a few days before this happened for the first time - but filled it up and drove all over the place and the truck ran fine.

Mod (Ret.)

Check for air intake leaks. Maybe a loose clamp at the air filter box, or tube running to the throttle body?

If no, remove the tube, and remove the throttle body. Clean it with throttle body spray (do not use carb cleaner or engine degreasers; they remove the coating on the throttle body's flapper). You will most likely see a lot of carbon (black) build up on the back side of the throttle body valve; this can cause a rough idle, and poor fuel mileage.

Inspect all the wiring connections to the throttle body. You can also have a poor MAF (mass air flow) sensor. This measures the air flow coming into the throttle body. If its bad, it sends an invalid reading of air amount to the PCM (powertrain control module) or ECM (engine control module) that is used to adjust the correct fuel pressure to the injectors, based on how much air is detected coming into the throttle body.

Check for unmetered air leaks, check the MAF, check the throttle body. Check the air filter too.

chaoticsanity

Could also be as simple as changing the fuel filter. It's pretty simple to do yourself, just make sure you have the fuel filter clamp release tools.