98 won't hold an idle and stalls

[driftbendito]

This morning I went to start my 98 4.0 ohv explorer and encountered some problems. I can turn it on but the explorer will not hold an idle. It will idle extremely rough than just stall out. When I rev it, initially it is not that responsive but around 2000 rpm and up it revs freely. However, when I let off the gas the car goes back to rough idling. I noticed over the past few weeks that the idle was slightly rougher than usual and a little lower, but today the idle is very rough and the car can not be driven. What can possibly be causing this problem?

 

[hansvdweerd]

I've had a similar problem with my '98 Explorer XLT (SOHC) and posted on this forum about it. This is the thread:

http://www.explorerforum.com/forums/showthread.php?t=265806

There's also an excellent write up by 2000StreetRod:

http://www.explorerforum.com/forums/showthread.php?t=261439

In my case the problems would go away once the engine had warmed up. How is that with your Explorer?

After I replaced the upper and lower intake manifold gaskets the problem was solved!

 

[alohamonte]

I have an OHV. For me it was several things since I had a weak idle and no engine codes to help direct me. Try these steps in this order.

1. Tune up. Plugs, Wires, Fluids, PCV, Fuel & Air Filters.
2. Replaced Mass Air Flow Sensor, Throttle Position Sensor, and Idle Air Control Valve. You can remove and clean all these components you might not need to outright replace them all.
3. Replaced Upper Intake Gaskets & Cleaned Injectors and new injector o-rings
4. Replaced EVAP Pressure Sensor and Control Solenoid

Idle is near perfect.

 

[hansvdweerd]

I have an OHV. For me it was several things since I had a weak idle and no engine codes to help direct me. Try these steps in this order.

1. Tune up. Plugs, Wires, Fluids, PCV, Fuel & Air Filters.
2. Replaced Mass Air Flow Sensor, Throttle Position Sensor, and Idle Air Control Valve. You can remove and clean all these components you might not need to outright replace them all.
3. Replaced Upper Intake Gaskets & Cleaned Injectors and new injector o-rings
4. Replaced EVAP Pressure Sensor and Control Solenoid

Idle is near perfect.

That's a good list! I stopped after replacing the gaskets as the idle was okay again. I will be replacing the PCV-valve in a few weeks, because I think it's never been done before (97000 miles).

Just a tip:

When I was replacing the gaskets for the air intake manifold I noticed that the previous owner had unfortunately only did half a job... He replaced just the upper gaskets and not the lower. And it were in fact the lower gaskets that caused the rough idle and stalling!

So when you're taking apart the intake manifold you might just as well do all the gaskets. The gaskets were about $ 20,00 (upper and lower).

 

[marragtop]

Check the vacuum lines on the vacuum tree located drivers side by the firewall. If one of those lines is off, it will give you what you are describing.