Hey guys im new to this forum and could really use some help. I just bought a 1994 Ford Ranger 2.3 manual transmission and it has a bad idle and stalls. Once i get it moving and its no longer idling it drives fine. When at idle it will run rough for about a min until it finally stalls. First thing i did was tested the egr with a vacuum pump and when applying vacuum to egr engine condition did not change. It should have stalled right there but it dint. replaced it and still does the same thing. I ran it with the vacuum line disconnected to the egr and it runs the same. I cleaned the iac and that dint help. Gave it some taps while running and no change. Ran it with the maf unplugged and it revs a little higher for about 30secs and then goes back to running poorly and stalls. Checked for vacuum leaks with brake cleaner and no luck. No CEL on and i dont have a scanner for 94 to pull codes if it did. Checked timing belt and timing marks are dead on. Could really use some help here im running out of ideas.

 

Normal cold start routine for fuel injected engine, not just Ford, is:
Turn on key, crank engine
Fuel pump comes on for a few seconds to prime system pressure

If engine starts idle should go up to 1,500+ RPMs, that's the computer opening up the IAC Valve all the way for starting.
Idle should then drop to about 1,100 RPMs, this is based on temperature of engine, colder temp higher idle.
The temperature of the engine comes from the ECT sensor, this is a two wire sensor only connected to the computer.
The dash board temp gauge uses a one wire Sender, not a sensor.

As ECT sensor warms up with the engine coolant the computer lowers the idle until target warm engine idle is set, 700-750 RPM for manual trans, 800-850 for automatic.

If you are not getting the high idle on cold start then either the IAC valve or ECT sensor is not working.

Does the CEL come on when key is turned on?
It should and then go off.

The O2 sensors can't work below 650degF so are not used during warm up, computer runs rich fuel mix based on MAF, RPM and throttle position until O2 sensors can be used.

Warm up stage is called Open Loop since computer isn't getting any feedback from O2 sensors.
Most systems do not used the EGR system in Open Loop, since the warm up time is only 5 to 8 minutes and the system is running rich, high NOx levels and pinging are not an issue during warm up, so EGR is not needed.

Once O2 sensors are working the system switches to Closed Loop, computer bases fuel mix on feedback from O2 sensors, and uses EGR system to prevent cylinder overheating from lean fuel mix.


EGR valve not stalling idling engine when opened is a problem, when you removed the EGR valve did you inspect the tube to exhaust manifold?
Manually opening EGR valve should cause engine to stumble and die if opened far enough and long enough.

'94 2.3l uses Dual spark plugs and Dual coils, and an external ICM(ignition control module)
In '95/'96 the ICM was built into the computer, EEC-V

The standard tune up should probably be done since this is a new truck for you, it isn't cheap because of the "dual" spark plugs and wires.
Coils and ICM can be tested with volt ohm meters, some auto parts stores have ICM testers

I would at least pull out 1 spark plug from each cylinder and inspect it, google: spark plug condition

 

Coil packs have been replaced and so have plugs and wires. During a cold start it does idle higher and it doesnt stall. Once its warm and stalls i can restart it and it will immediately run rough and stall after a while. CEL bulb does come on with key cycling but does not illuminate when running. I dont believe its going to be a ignition problem because if it was it should run worse at higher rpms. I already replaced the egr with a new one.

 

So just an update. I performed a smoke leak test and found I have a leak from my underneath my throttle body. There is a vacuum line with nothing connected to it. I checked and can't find anything it connects to. I plugged it up and it still continues to run the same. Any idea what's supposed to plug in there? I know right next to it is the vacuum line for the vapor canister to the manifold.

 

Another update i found out the vapor canister is supposed to go to the throttle body. I swapped over the line from the plenum to the throttle body. I plugged up the line from the intake plenum and the engine runs great now. I just need to know whats supposed to go to the the plenum. I found a picture online of a ranger plenum so you can see what line im reffering to.

 

Larger vacuum lines are for PCV valve and Power brake booster on most engines.