Stumbling

[Phantom5oh]

I just picked up a 94 Explorer V6 for real cheap, but it does need some work. First on the list is I have a problem with stumbling at idle and at low speeds. It is coming from the engine not the transmission I know that and it seems to be running a little rich. Any ideas on where I should look?

 

[410Fortune]

Does it have a Check Engine Light?

First thing to do is a FULL TUNE UP.
It could be as simple as old spark plugs, or bad gas.

If the CEL is illuminated pull the codes.

The next thing to do is clean the intake, throttle body, MAS, and IAC valve. Reset the computer.

How many miles are on the truck?
Stumbling is typically a fuel issue, too rich like you said.
too rich is usually computer related (MAS, 02 sensors, computer itself) on these trucks, UNLESS the fuel pressure regualtor is bad. You can check the fuel pressure to determine.
Also a leaking intake manifold gasket or injector can cause issues, also a bad cat converter can cause power loss.


Alot to think about I know, just trying to get you started in the right direction.
When you say stumbling I assume you mean the RPM's are erratic, from 500-1200 at idle? then when you hit the gas it hesitates?

 

[Phantom5oh]

No, I guess it runs more like it has a dead cylinder, that sort of rough. I doubt it is dead though because when you get on it it goes good. It has 178000 miles on the clock but like I said it was cheap. Should make for good inclement weather transportation if I can get the thing running right.

 

[MrShorty]

When my '92 lost two cylinders it still ran well. If you think it's missing, start with a cylinder balance test to identify which cylinder isn't firing. If the miss can be isolated to one cylinder, then check for spark to that cylinder, check that that fuel injector is working, and run a compression test.
Beyond that, run the EEC-IV self-tests and test the fuel pressure, just to round out the set of standard diagnostic tests performed.