Explorer XLT 2001 Idle Problem

[jos]

Hi,

I don't know if it's a common Explorer problem or one of those nasty "can be anything" problems. It's a 2001 Ford Explorer XLT 4.0L 4x4 SOHC.
It began quite a while ago: sometimes I had to start twice to get the engine running. That lasted for a couple of days and then it was ok for a month or more. And then again the starting problems. Apart of that the vehicle seemed to run perfect, until the fuel pump died. I replaced it and the problem seemed to be solved. But not long after I had the starting problems again. Not everytime, but more often. And now the vehicle is rough idling and over 3500 rpm it starts rough running too (like no power). I replaced the spark plugs and wires and it seemed to be ok for a short time and now I'm having the same problems again. I would appreciate some help where to start troubleshooting.

Thanks in advance

 

[swshawaii]

Narrow it down by scanning for trouble codes, check engine light or not. Unless erased they will be stored in memory.

Call around, most larger auto parts stores will check as a free service. Write the code NUMBERS down and post them.

OBD-II Diagnostic Trouble Codes (DTCs)
http://www.explorerforum.com/forums/showpost.php?p=2054355&postcount=2

 

[2000StreetRod]

Airtex fuel pump?

Did you happen to replace the old pump with a new Airtex pump? Some members have experienced rapid failure with those pumps. I suggest checking the fuel pressure.

 

[jos]

Thanks for answers. Yes, it is a new Airtex pump. I will do a fuel pressure check and post the result. There was the Check Engine Light on a while ago too. I did a scan and it showed a P0301 error. I checked the spark plug and the wire, erased the code and the CEL didn't stay on since then.

 

[jos]

Just did a fuel pressure check. The fuel pump builds pressure every time I turn the key, but the pressure goes down right away. Where should I go from there?
Thanks again for help.

 

[2000StreetRod]

65 psi

On a 2001 the fuel pressure should be 65 psi +/- 8 psi when the engine is running. When the ignition is switched from off to on the fuel pump only runs for a couple seconds. After switching the ignition off and on three times the fuel pressure should reach 65 psi. The pressure should drop slowly probably still being 30 psi after 5 or 10 minutes. If it drops rapidly then there may be a leak in the external lines or fuel injectors. Or, the check valve in the fuel pump assembly is stuck open. When you replaced the fuel pump were any of the hoses split?

Did you replace the entire assembly or just the pump? The upper hose above the fuel pressure regulator may be split.

 

[jos]

I replaced the entire assembly. I'm afraid I have to take off the tank again and check. Thanks for your help.

 

[2000StreetRod]

defective check valve

The check valve is part of the assembly and not serviceable. If your fuel pressure drops rapidly when the engine isn't running you probably have a defective check valve.

 

[jos]

After I replaced the entire assembly, the fuel gauge is showing more than full and doesn't change, it's stuck in this position. Could that be related to the check valve? A bad electrical connection maybe?

 

[2000StreetRod]

fuel level sender

The opening in the fuel tank is only slightly larger than required for the fuel assembly to pass thru it. The fuel level sender is simply a movable wiper on a resistance strip and is easily bent away from making contact if extreme care is not used when installing the assembly. Or the float arm could be jammed in the full position.

The check valve is totally mechanical and independent of electrical circuits. It can be tested by trying to force air into the fuel hose in the opposite direction of fuel flow. Little or no resistance means a defective valve.

 

[jos]

I just finished replacing the fuel pump again .... fuel gauge seems to work now, but still pressure dropping down rapidly, rough idling and rough running at 3000 rpm and up. What to check next? Thanks for help!

 

[2000StreetRod]

fuel pressure readings?

What is the fuel pressure after turning the ignition off and on 3 times?
What is the fuel pressure with the engine running at idle?
What is the fuel pressure 3 minutes after shutting the engine off?

 

[decipha]

the only way to check fuel pressure is to have a guage on it at WOT

if the pressure doesnt drop at the top of 2nd its perfectly fine

more than likely you have a failing coil or the like

 

[jos]

Fuel pressure check:
turning key three times (no starting) it went up to 64 psi. After a couple of seconds it dropped down to 56 psi, then slowly (about 5 min) down to 50 psi. Another 5 min down to 46 psi.

When I started the motor, idling was ok now and the gauge showed 64 psi. Over 4000 rpm the vehicle was running rough and the needle jumped slightly. After shutting off the motor the needle went down to 59 and stayed there and didn't move anymore (I released the fuel pressure after about 1/2 hour).

When driving the vehicle, things go worse, when the motor is warm.

 

[2000StreetRod]

good check valve

For those numbers your fuel pressure is good and the fuel pump check valve is working fine. On 2001 and later models there is a rev limiter set to about 3,000 rpm when the transmission is in park or neutral.

What are your current symptoms? If the engine idles rough after warming up you could have a faulty engine coolant temperature sensor. If the sensor reports the engine coolant as cold but the engine is actually warm the fuel mixture will be too rich. If you don't have access to a scanner to read engine coolant temperature via the OBD-II port then check for black smoke exiting the tailpipe.

 

[koda2000]

No one has mentioned possible leaking intake manifold O-rings. They make for difficult staring, stalling and a rough erratic idle especially when the engine is cold.

 

[jos]

When driving, the truck is having pretty similar symptoms as with the Airtex pump (except the fuel gauge is workig now): rough running above 3000 rpm, not much power accelerating and uphill, rough idling, especially when engine is warm.
Update: now the vehicle stalled when idling.

 

[Millwall]

Have you changed the fuel filter?

 

[jos]

Have you changed the fuel filter?

Yes, I changed it, when I replaced the fuel pump the first time (Airtex), that was in September this year. After that the vehicle was running fine for almost two month.

 

[Millwall]

if your fuel pressure readings are standing up to scrutiny it may be worth linking in some clear pipe on the fuel line and see if your drawing in air or dirt along the fuel line somehwere.