93 2.3L has check engine light but no codes even mechanics stumped

[dguett]

HELP, my 93 ranger 240M miles, has a check engine light that will eventually go out after it runs for an unknown length of time but never has a code. When the light is on it runs terrible and won't idle. Finally when the light is off it runs as good as it every has. Mechanics say it would cost to much to try and locate the problem, especially because of the age of everything.

HAS ANYONE HAD A PROBLEM LIKE THIS??? Need help because I don't want to shoot "Little Grunt"

 

[fastpakr]

Have you tried getting the codes yourself, from all three sets?

 

[Captain Ledd]

Is a '93 OBD1?

 

[rusty ol ranger]

Is a '93 OBD1?

Yes.

 

[black_demon69]

http://https://www.freeautomechanic.com/diagnostictroblecodes7.html

This might help

 

[85_Ranger4x4]

Is a '93 OBD1?

OBDII came out around 95-96.

This might help getting codes.

http://www.therangerstation.com/how-to/ignition-charging-computers/

I don't know a whole lot about OBD1 but I don't know if they actually store codes.

 

[fastpakr]

The way I remember it, the continuous memory codes can be set if a running code has been triggered a certain number of times. If you're lucky, you'll find those after pulling the engine off codes.

 

[RonD]

Welcome to TRS

Just to be clear it runs poorly cold(CEL on), but then runs OK warmed up(CEL off)?

Or does it run poorly(CEL on) even after a restart, engine still warm?

CEL will come on when engine is misfiring, and not always set a code since driver can feel it misfiring.

If only cold start is a problem then could just be ECT(engine coolant temp) sensor is stuck on Warm Temp, so computer doesn't know engine is cold.
And cold engines need to be Choked or they won't idle, and O2 sensor can't work until it gets above 600degF.
ECT sensors can be tested but at $8 they are often just replace on spec
1991 will have TWO temp devices on the engine
ECT Sender for the dash board gauge only, 1 wire
ECT Sensor for the computer only, 2 wires

Also IAC Valve may be stuck or bad
IAC(idle air control) Valve is what fuel injected engines need to idle, no Jets so can't use an "idle screw"
Computer controls the IAC valve to set idle RPMs
Key on opens IAC Valve all the way
After startup computer closes it a bit to set Cold idle then continues to close it as engine warms up to set warm engine idle.
There are just 2 bolts that hold IAC Valve on the upper intake and a 2 wire connector
Easy to remove and test
Take it off and plug in its wires
Turn key on/engine off
IAC Valve should be open all the way now
Unplug its wires and it should close, internal spring pushes it closed
Plug it back in and it should open all the way again
Repeat as you see fit to make sure it is not sticking
Replace if not working at all, also test that wires have 12v and ground with key on/engine off



These computers had capacitors that could leak after 20+ years, you can remove the computer and open the top, and have a look at circuit board, look around the Blue capacitors for damage.

Good one seen here: http://www.auto-diagnostics.info/ford_eec_iv

Damaged one seen here: http://support.moates.net/capacitor-repair-ford-a9l-ecm/

leaking Caps can cause oddball issues

 

[adsm08]

OBDII came out around 95-96.

This might help getting codes.

http://www.therangerstation.com/how-to/ignition-charging-computers/

I don't know a whole lot about OBD1 but I don't know if they actually store codes.

The way I remember it, the continuous memory codes can be set if a running code has been triggered a certain number of times. If you're lucky, you'll find those after pulling the engine off codes.

EEC-IV (OBDI) is pissy about how, when, and why it will store codes.

The condition has to be there so many times, for so long, before it will store a memory code, and my experience has been that there is little rhyme or reason apparent in it.

 

[decipha]

just pull the codes while its acting up and you'll see the code