94 Explorer sometimes won't start or idles rough

[kylegrand]

I have a 94 explorer with a 4.0 Somedays it won't idle when i start it unless i hold my foot on the excelerator. Then last night, it wouldn't start for me, turned over great just wouldn't start. I came back about a half hour later, and it fired right up. Could I be looking at a bad cam position sensor? Thanks

[shorod]

Sounds to me like a failing fuel pump.

You need to check for fuel and spark those times when it won't start. If you have spark, it won't be the cam sensor. If you have fuel in the cylinders, it won't be the cam sensor. If you have good spark but low fuel pressure, it's likely the fuel pump, trusting that you do keep on top of the routine maintenance/tune ups which should include a fuel filter.

-Rod

[TheBigfut]

Have you tested the IAC(Idle Air Control) or the battery itself? Also when was the last time you had a tune up or cleaned the throttlebody or mass air flow sensor? Simple things I do as maintneance that might contribute or eliminate some of the issue.

[kylegrand]

I'm not real sure about the maintanance of that sort. I just bought it a week ago. It has been taken care of though because I got a stack of almost 50 pages of service records from the local dealer on work that has been done on the vehicle. I'll look through them to see if anything of that sort has been done.

[kylegrand]

Just thought i would add as it didn't want to start today. It only does it when it is pretty cold, like below 20. Otherwise when its warm it starts fine. The battery is good and it turns over great just doesn't want to start, never tries just wont start.

[danilh]

sounds like it might be IAC? do you have check engine coming on? Or perhaps OBD1 is less reliable, too bad if so, my 95 with 4.0 comes on and off for various reasons and it drives me crazzzyyy

[kylegrand]

There were no codes and the check engine light never comes on. I've narrowed it down to the fuel pump or filter. When i turned the key on, it took over a minute for the fuel pump to shut off. Do you think it is the pump, or possibly just the filter?

[shorod]

I don't believe the '94 uses any sort of fuel pressure sensor, so the pump should still only run for the 3 seconds or so. It won't keep the pump running long enough to build pressure, so I think you have some other issue, possibly in addition to a fuel pump or filter.

-Rod

[discnik]

If I may add my two cents. Have you checked the fuel pressure regulator ?

[kylegrand]

Hi,
I haven't checked the fuel regulator. It still idles rough sometimes, but not always. I'm thinking there might be something in the tank because it ran fine after I put a couple gallons in it. What do i need to do to check the idle air control.

[shorod]

One way to check the IAC would be to turn the steering, with the Explorer running, all the way to one of the steering locks and hold it there for just a couple of seconds. If the engine stumbles or the engine speed drops while at the lock, the IAC may not be doing its job.

-Rod