Hard to start when warmed up... (1 Viewer)

[tputterman]

First thing in the morning my 3.4 starts right up. Once I get to running temp and turn it off it takes 3-4 cranks to get it started. Within the last 10,000 miles I have replaced all spark plugs, injectors, coils, fuel filter, timing belt, and water pump. Could it be vapor lock? Stuck injector so the fuel is back flowing? Bad fuel pressure regulator? I don't see or smell any fuel leaks. The only time I smell fuel it first thing in the morning when I start it and it is coming from the exhaust tail pipe and isn't very strong.

 

[Mike Shull]

It sounds like it could be vapor lock, but it could also be a dirty or failing sensor that doesn’t read correctly when warm. The usual sensors that might cause hard starts would include the MAF, crank and cam sensors. Have you looked inside of your air intake to see if it is dirty?

If the above checks out, I’d recommend putting a fuel pressure gauge on the fuel rail to measure during your hard start scenario. Take a baseline when cold, too. I don’t remember whether you can get fuel pressure readings from an OBD2 scanner on that model, but you should be able to see other sensor readings. I’d also check those cold and warm to look for an anomaly.

 

[Mike Shull]

Also, these engines are highly dependent on a healthy electrical system, too. Have you checked voltage when warm and cranking? Even a small voltage drop could cause a hard start.