Sounds like you have a lot of voltage problems, the last time I heard all of these the guy changed all of the sensors and still had the same codes.
He changed the PCM (EEC) and it was fixed. You can get one from a salvage yard for $30.00 to $60.00, just get one from within one year of your truck with the same engine, transmission with the same type air sensor map/maf sensor.
I hate to say that is your problem but it sounds like it to me.

Does your fuel pumps run all the time the key is on without the engine running?
Is your ref voltage right at 5VDC?
If yes to the first question and no to the second then it is the PCM (EEC) for sure.

 

I hate to say it but I think your wrong on this one subford. I find it very hard to believe that a truck that runs normal 95% of the time has a major computer problem. If a truck has 5 codes out of who knows how many possible codes I just doubt its the main computer. If you are not going to work through the codes then what good are they? One of the 5 codes I have just says I am not in park or nuetral during the test (not a big deal) so technically I have 4 codes worth looking into. I also thought it was a coincidence that I unplugged the Map sensor and reconnected it and then I get a code on the Map sensor. I think I am going to clear the codes and see which ones come back and go from there. You also said don't erase codes by disconnecting the battery to avoid losing KAM memory then what happens when you replace a battery?

 

Could be and I was just relating what happened to another member of this Forum. What I was getting at is when all of the sensors that use the 5-volt reference voltage report errors at the same time then most of the time the 5-volt reference voltage is off. This can happen because it uses Electronic Capacitors for the filters. When Electronic Capacitors start going bad they can and do heal themselves and then brake down again. But eventually they will be bad all the time.
You can fix this by replacing the capacitors as the rebuilders do and there is a web site that will show you how or you can replace the computer.
That is why I told you to measure the 5-volt reference voltage when it was acting up. This will tell you if it is right at 5 volts or not.

When I change a battery I stick a 9-volt battery in the lighter plug and this will also keep all of the radio stations in memory for the radio. Or you can drive 5 miles at hi way speed for it to relearn your habits while you reset your radio.

The questions above were also to help find out if the computer was bad or not and you did not answer them.

 

Is there a particular test point/port for the 5 vlt reference that eliminates most of the wiring?

 

Most of the time I use a breakout box to check all the voltages and sensors and you do not have to look all over the engine for them.
But without one you can back probe any plug that uses the 5-volt reference voltage for its sensor.

Sensors that have plugs with the 5-volt reference voltage are:
The TPS, EGR (EVP) and MAP if you have one.

 

That box is the holy grail of ford tech tools, hope you keep it in a safe.

What I was wondering is did ford put a plug or connector on a pigtale in the harness some where up around the diagnostic connector. A short run to the pcm that eliminates most of the wiring when doing voltage test. It would seem logical to normal persons like us but maybe not to corporate mind/cost control.

Anyway I thought there might be one in that area that dracip might find easier than going down to the individual component to back probe.

 

Yes there is the engine plug C101 on the engine side of the engine fuse panel (box), if you unplugged the engine you could test it there and the only sensor still on the 5V REF would be the MAP sensor. It would be the Brown wire with a white stripe # 351.

I do not have a pin-out of a 1992 engine plug but here is a 1994 and I think they would be the same.
http://i54.photobucket.com/albums/g9...l/1994C101.gif

 

subford, please see see replys 4 and 5 on this thread and I am unsure of the reference voltage. After coming home today I had to go back out again and the truck started doing its flooded rich thing so I immediately turned off the engine and went under the hood and disconnected the ect sensor. The truck then started fine and CEL came on due to the unplugged sensor. I think I'll invest in a new Ford ect sensor tomorrow. What do you think? Thanks again for all your help on this -Tom

 

I think it would be a good idea to change it (ECT sensor with two wires) and I think I said something about that in reply #12.

 

It seems to me, it's cold starts that are giving him is problem, at least that's the way I keep reading it. It sounds to me like an injector(s) may be leaking down overnight or something. He's getting a lotta raw fuel on cold starts.

dracip, have you noticed any fuel smell in your oil? ****** the stick out when the engine is cold, and see what the oil smells like. There should be no gasoline smell to it at all. Obviously, when you shut the engine off, the fuel pressure at the rail shouldn't go away instantaneously, unless you have something wrong somewhere in the fuel delivery system. Mine holds pressure for at least 30 minutes after pressurizing, and is still at about 1/2 pressure an hour later. A quick drop in fuel pressure after shutting off the engine is a pretty good sign of a leaking injector or faulty fuel pressure regulator. Finding which one(s) may be a bit of a challenge, though.

The 4.9 I6 runs a higher fuel pressure than our V8's, but I forget the exact numbers. I think I'd do some diagnostics on the fuel delivery system after resetting the codes. How many miles are on the truck? I have a '92 "southern truck" also, but it's got the 5.0 and M5OD, otherwise, we could compare notes.

If you want to check for leaking injectors, try this little test. You don't normally seem to have any issues starting when it's warm. There's a built-in feature that will shut off the injectors at WOT during START conditions. Next time you're pretty sure it will start up ok (while it's warm), push the throttle to the floor and hold it when you try to start the engine. If it starts, you quite possibly have a leaking injector, or too much pressure at the fuel rail (take your foot off the throttle quick, too). The injectors should not fire at WOT during start. Like I said, I don't remember the numbers for your I6, but fuel pressure should be lower when idling (20 inches vacuum) and higher for WOT (0 inches vacuum). It could also be that fuel is collecting in the vacuum line on the FPR while it's sitting, but that would probably be worse on a hot engine. When you start up cold, it's getting too much fuel from somewhere. I remember reading that you have to floor it to get it to start when the problem does occur. The reason it's cranking then is that the injectors are not firing. Not every problem on these trucks is electronic.

 

Thanks old paint but my problems are exactly the opposite - I have warm starting problems - it alway has started from cold fine. I will post results of ECT sensor change over the next few days. Thanks to all - Tom

 

dracip: Regarding reference voltage. The computer is hooked up to a sensor, just about any sensor that it needs to monitor and it does so "looking" at how much change in voltage there is on that sensor. In this computer that runs the engine it is 5 vlts DC. Thats the refference voltage. The most common one talked about on this board is the TPS, or throttle position sensor. When closed & adjusted properly it should read .99 volt. When wide open, the computer should see 4.98 volt & knows that you've got your foot on the floor & it acts accordingly. Hope I got that straight & not bas-ackwards.

What sub ford wants you to do is the next time you've got a warm engine/ no-start condition is to measure the refrence voltage(See post #22) That your computer is putting out. Preferebly before you spend money on parts, but certainly after if the ect sensor doesn't do it for you.

 

Went on Saturday to Ford dealer to buy ECT sensor but of course they didn"t Have it - you know those boxes 1"x1"x2" take up so much space that they would be overwhelmed to stock anything that small. This was also after they said they had it and I drove ten miles. Dealers! I have now been driving the truck with ECT disconnected and it runs beautiful - have not had any warm rich flooded starting conditions. 2 questions 1. Can you test an ECT sensor to know for sure if its good or bad? 2.A parts store will probably have an ECT sensor in stock but would you recommend staying with genuine ford part on this? Thanks

 

Engine Coolant Temperature (ECT)
This measures the temperature of engine, and has a great impact on fuel ratio.
You can go here for information on testing:
http://fordfuelinjection.com/index.php?p=28
I would prefer the genuine ford part but the NAPA parts store part may work well also.

 

You can get a Motorcraft sensor at Advance Auto, but make sure you tell them you want Motorcraft, or they'll automatically try to save you some money with the cheap stuff. Advance carries a pretty good line of Motorcraft parts. Enough that I haven't had to get anything from a dealership in a while for parts. The ECT is basically a 2 wire RTD (Resistive Temperature Device). Not much can go wrong there. If the truck ran really great with it disconnected (should have turned on the CEL) then you're running on a very rich mixture, which should make it stutter a little and rob power (my ECT croaked one time). This further suggests vacuum leaks if it was running smoothly. Typically, though, if you're getting multiple codes that point at everything that uses the 5V signal supply, then chances are the 5V supply has died in the ECM, or a wire has corroded or broken. How clean is the area where the harness comes through the firewall? Got a bit of mud there?