Hard start

[justins81213]

Not really sure if I'm posting this on the right forum but I have a 2006 Ford ranger sport 3.0 RWD. It starts right up Everytime but when I first start it,it seems like it has a hard or rough sounding start like it's drawing to much air or gas maybe not sure. My rpm will jump to 2000 then drop right to 1500 and after about 10-15 seconds will drop to 1250 or 1000 and sounds fine from there on. Could this be the iac valve? Any suggestions to narrowing down the problem would be great. It doesn't do it every start usually just once maybe twice a day.

 

[RonD]

I would first test if fuel pressure is dropping to low when engine sits for longer than say 5 hours
2006 runs 55psi fuel pressure, when off the fuel pressure should hold above 30psi for many MONTHS
When you turn on the key the fuel pump only runs for 2 seconds, its a safety thing, and then will not run again until RPMs are above 400, engine started
If fuel pressure is leaking out when truck sits then that 2 second run time might not be enough
So turn key on then off, repeat 3 times, 6 second run time, THEN try to start the engine and see if its better


If that doesn't help then I would change the ECT sensor on speculation, its not too expensive

ECT sensor tells the engine computer how much Choke to apply to a cold engine
Cold engine needs to be choked, computer does this based on temp it gets from ECT sensor
If ECT is showing a warmer temp than actual temp there is not enough choke applied for quick start up, but after a few seconds the cylinders are hot enough to not need full choke

There are two temp devices on the 3.0l engine
ECT sensor uses 5volts and will have light green and gray wires, only used by the computer
ECT Sender uses 12volts and will have red and black wires, its only used for dash board temp gauge

So they are not interchangeable

IAC Valve reads like it is working OK
It should be wide open for start up, so 2,000RPM surge
Then computer will start to close it for cold engine idle, 1,100-1,500rpm depending on outside temp(ECT sensor Temp)
Then as ECT/engine warm up the computer continues to close IAC Valve until warm engine idle is set, approx. 750-800 for automatic trans, lower for manual

 

[justins81213]

Just tried the key thing didn't seem to do anything different it's usually just the first start of the day it does it. Maybe I'm just over thinking it

 

[rusty ol ranger]

Try holding the throttle down about 1/4 way when you cold start it.

If it fires right up id blame the IAC

 

[justins81213]

Ok I'll try that tonight when I get off work

 

[91stranger]

I was thinking fuel filter or pump as well. Definitely need to get a fuel pressure reading. If you don't have a gauge you can just press the Schrader valve with a screwdriver with the key on and if gas hits the hood then you got good pressure. If it barely comes out with the key on then its either a plugged filter or bad fuel pump.

 

[justins81213]

Just put a new filter on less than a year ago but I'll check the pressure out

 

[justins81213]

Tried the throttle thing and it pretty much started right up and just revved and rpms went to 3000