2004 Explorer: Crank but No Start

[dfryatt]

Hey I'm glad you guys are here to help!

I have a 2004 Explorer 4.0L RWD with an issue I can't figure out.
It started about 2 months ago - the engine seemed a little off, hesitant if anything - nothing major. Then it gradually got worse and worse to the point where i couldnt get the car to go about 2mph. It seemed like it wasnt getting fuel and my code reader was showing that the o2 sensor was bad.

-I replaced the o2 sensor and then after that the car wouldn't idle however the coder reader showed now signs of an o2 sensor failure with the new one installed.

-after that the code reader showed a weak duty cycle from the fuel pump so i replaced that and the fuel filter with no positive or negative change in the vehicles performance. (no idle)

-I then installed a new coil pack with new spark plugs and wires and STILL no idle. My code reader also isnt picking ANYTHING up from the computer probably because we cant run long enough to self diagnose.

-I am getting little to no vacuum at the fuel pressure regulator. I am assuming there should be at least some vacuum there during cranking - ay thoughts??

My next thoughts are somehow finding the vacuum leak, then replacing the MAF, TPS, or IAC but i wanted to get a second opinion before i go spending any more money just to troubleshoot.

Oh and btw- the air filter is clean, i'm getting spark and fuel as well.

 

[imp]

Pull the sparks plugs and do a compression check. I'd be leaning toward a possible grenaded piston dome.

Did the engine make any unusual noises as the trouble grew "worse and worse"? imp

 

[mr2fix2it]

sounds to me like a clogged catalitic converter remove the o2 sensors on the front of cat or drop exaust pipe and see if it starts if it does then you guessed it the cats are bad

 

[manaen]

you will not have much vacuum if the engine will not even idle properly. Run a Fuel pressure test to make sure your pump/FPR are working correctly you don't need it to run for this. What was the O2 sensor code that your received. Very rarely do the O2 sensors actually fail but they are almost always the first indication of a lean or rich condition. If you had a lean condition code then I would search for a vacuum leak (hose, intake gaskets) or low fuel pressure. If you had a rich condition then it could be too much fuel pressure, no spark in one or more cylinders.

Edit: if you don't remember the code, pull the plugs and read them it will tell you if you are lean or rich.

Start with the basics before suspecting the cats. With modern engines the mixtures are so precise that cats generally do not clog unless you ignore a code and drive the vehicle for extended periods.

 

[mr2fix2it]

read his first question this all started 2 Months ago and now it dont start i still say start by dropping cats is the easy thing to do!

 

[dfryatt]

Im getting good pressure out of my exhaust pipes during cranking. I know the cats arent clogged. I have a feeling that its a vacuum leak - are the intake mani. gaskets notorious for going bad? The plugs read rich - as hell. They are soaked which leads me to believe that the FPR isnt getting any vacuum causing high fuel pressure. Check me on this but i believe thats how it works.

 

[dfryatt]

I dont think its a grenaded piston dome as there is no evident noise cranking around in there during crank - i do think i have to do a compression check either way.

 

[manaen]

you need to run a fuel pressure test

 

[dfryatt]

I will do that after work today. Does anyone know off hand what the fuel pressure should be at?

 

[matt0248]

Disconnect the MAF and see if it starts. It would take an extreme vacuum leak to cause a no start. If the plugs are that fuel fould the need to all be taken out and cleaned or replaced.

 

[dfryatt]

I did that already actually. It didn't make any difference. All the plugs are brand new and firing fine (I tested cylinder 5). Will the car start without the MAF?

 

[manaen]

I think you should have a 62psi system

 

[dfryatt]

ok new developement - I came to check the fuel pressure today and i cranked it a few times - still acting the same as it has been for the last few days BUT THEN i went to start it again and it wont even crank now. I can crank it from bypassing the relay, tried swapping it with another relay and it still wont work. any ideas? any body have the wiring diagram for the ignition switch???