DTC 21 and 14, hard start, dies when given gas

[slag]

PROBLEM FIXED!!! DTC 21 and 14, hard start, dies when given gas

My father called me saying he had explorer problems. He is getting codes 14 and 21, both related to the ignition. The explorer is hard to start, and once it starts, runs rough for a while. Then it will smooth out. If you give it gas, it will die instantly. Sometimes, if you feather it enough, it will run, albeit super rough.

He also had codes 51 and 61, but those cleared and did not come back.

This is a 1991 XLT.

Ideas? Aside from the DTC's it totally sounds fuel related to me, however, the error codes point to an electrical fault of some sort with the ignition. Where would you start troubleshooting?

 

[MrShorty]

What portion of the test did those codes come from, KOEO hard fault, KOER, or continuous memory. Because you didn't say, I'm going to assume they are continuous memory 14, and KOEO hard fault 21, and that the KOER test wasn't performed. That said, here's what I'd do:
1) Clear up the KOEO 21. It, like the vanishing 51 and 61 is an ECT code. Usually it's a result of running the KOEO test on a cold engine. Warm the engine up and repeat the KOEO test to see if the 21 goes away. If it doesn't go away, then diagnose the ECT sensor/circuit to find out what's wrong.
2) After getting a pass code for the hard fault KOEO codes, then run the KOER test. May not be any useful information here, but perform the test to see what trouble codes you get. Diagnose and resolve any KOER codes until you get a pass code for the KOER test. If you only get a "can't control RPM" or other real vague code, then turn your attention to the CM 14.
3) CM 14 points to a fault in the ignition system. Could be a crankshaft position sensor, bad ICM, bad coil, or others. When you reach this point, I'd go to the library, find a good manual with the circuit pinpoint tests, and see what they say about diagnosing a CM 14.

Good luck.

 

[slag]

update, finally got to look at the explorer last night and it baffles me as to what the problem is.

He's still getting codes 14, 21, and 51, even when the explorer is warm, but no CEL.

code 14 is the first code, then there is a space with a single beep, then the other 2 codes.

Because I had some spare parts, we swapped out the following with no change in condition:
Ignition control module (off my 92 x), TPS, IAC, MAF sensor, Crank position Sensor, Coil pack block, and fuel pressure regulator.

The car starts up and idles like crap for awhile--then smoothes out. If you give it any normal gas at all, it will stall out and die on you. If you lightly press the gas and work your way up, it sounds great. If it stalls out on you, its a byotch to start back up, but will eventually start up. If it were a carburated vehicle, I'd say its flooding out (sounds like its flooding and light fuel smell), and then the hard start is because its flooded, but I am at a loss. My next step is to buy a used ECU to see if the computer has gone south. If that doesnt change anything, I'll go to new plugs/wires and possibly change the fuel filter and/or drop the tank.

I'm totally at a loss as to the problem---its so weird. Also, the minute you put it in gear, it will die on you unless you are really lucky with the accelerator and can feather it just right

 

[MrShorty]

To clarify some terminology then:
14 is a KOEO hard fault code, which means the fault has to be electrical in nature
The single beep is a separator pulse that separates the hard fault codes from the continuous memory codes. This makes the 21 and 51 continuous memory codes.
Looked at some of the IDM code circuit tests for a '95 (wish I had the manual with me for a '91, so I could look up a code 14). An interesting part of the test was a test for a short between the IDM circuit and Vref. Vref is a 5.0 V reference signal generated by the PCM to monitor certain sensors, of which the ECT is one. This suggests the possibility of a wiring fault causing the computer confusion in both the IDM signal and the ECT signal.
At this point, I would strongly suggest a proper manual. Ford factory manuals can often be had on CD over ebay. Libraries often carry professional manuals (Mitchell or Motor) that will contain detailed circuit tests. Chiltons and/or Haynes publish a fuel injection diagnostic manual that, I believe, contains the circuit tests. To diagnose it properly, you're going to be disconnecting some connectors and probing with a DVOM for shorts and open circuit. A good wiring diagram will be important.
Basically what I see at this point: the rough running is from an inconsistent spark. The fuel smell is from fuel that isn't being burned because there isn't always spark.

 

[riverposie]

check the fuel pump & filter...i had same problem and it was just that...symptoms were the same...

 

[slag]

problem is fixed.

I dont know exactly HOW it fixed the problem, but the problem is fixed.

The main coolant temp sensor switch was faulty. Readings deviated way off the chart in relation to normal ohm readings.

Put a spare sensor on and the vehicle runs like a top with no error codes. Its been driven approx 100 miles since the sensor was replaced with no issues.

So, a faulty temp sender unit can cause dtc's that show ignition problems, even when there is nothing wrong with the ignition subsystem.

Slag