Ok guys, Go easy on me. I've never worked with a computer controlled EFI vehicle before. I'm willing and able to learn, and I pick up on things fairly quickly.

Symptoms: Truck starts fine, but wants to idle very low. It'll stall if I don't baby the pedal. Once it starts to warm a little, it'll stay idling...usually. I've noticed that the check engine light is lit, but will occasionally go out, and the truck will stutter and stall when it does.

Runs fine at any rpm over idle, but there is a slight hesitation at the pedal off idle.

I've found the test connectors.

How, and where do I start? If you want to use acronyms for the various components, that's fine, but refer to the full name of the component the first time so I'll know what you're talking about after that.

Take me one step at a time, and I'll post my complete observations and codes as we do this. I promise I'll do good research as we move along, so I hope not to waste anyone's time and efforts. I also take good pics.

Thanks for your help!

 

A great book comes with the code reader. You start by putting a battery in it. Then read up on the three types of codes, KOEO, CM and KOER.

 

I'm going to assume you either didn't get an instruction manual or you just want to know the basics from the truck side of things.

Take the truck for a drive for about 20 minutes. When you get back and the truck is still hot, start testing. Locate the STI (Self Test Initiation) connector and the single wire connector next to it. I your '92 it will be on the driver's side inner fender up close to the firewall. It may have a cover on it that reads "EEC-IV SELF TEST". Connect the reader with the engine off and the key in the OFF position. Turn the reader on and the key to the ON position. This will allow you to read KOEO (Key On Engine Off) Codes. To pull KOER (Key On Engine Running) Codes, you will need to start the truck and perform a series of dynamic response tests in succession to give the computer the "changes" it needs to "look at" to generate the dynamic response fault codes. This Site details the process.

 

Yup, I've been reading it this evening, along with reading the info at the link provided by greystreak92.

I guess there's no "tips and tricks" with this process. Manual is straight forward and easy to understand.

I guess there is no addressing the stalling issues until I can get codes. Man, I keep wanting to approach this like I would with my carbed '85. I know, I know...I'll get with the program! (no pun intended)

 

The reader will retrieve KOEO codes twice then will display "10" when it automatically goes to CM (Continuous Memory) retrieval with a "C" in the corner. If stalling while driving is the issue it may show in CM.

 

Got my codes for KOEO and CM. According to the manual for the reader, I stop here until I address these codes first.

KOEO: code 121 Closed throttle voltage higher or lower than expected.
CM: code 122 Throttle position sensor below minimum voltage

I went to ALLDATA and looked at the pinpoint tests for the throttle position sensor. Can anyone boil all that down to something I can understand? It seems that the pinpoint tests are more geared to a fully qualified mechanic. If someone can give me a simpler "do this, do that" test before I go buy a new sensor, I would GREATLY appreciate it.

I'll get better at this, I promise!!

 

I think I would clean the connector with electrical cleaner. The TPS is under the throttle body. Then apply dielectric grease. Clear the codes by disconnecting the battery about 30 minutes or use your code reader.

Drive it about 20-30 to let the system "Learn" again. Pull codes again. If the TPS codes show again replace it.

More info...Ford Fuel Injection » Throttle Position Sensor (TPS)

 

Is this the TPS? How does one remove such a thing?

According to what I've read, the wire color codes says this is what I'm looking for. Three wire connector, Orange, Green, and Black. Can this be removed without taking off the throttle body?

 

Yes that is the TPS on the bottom. There should be a connector within about six inches from it. Yes, the two times I replaced my TPS I removed the throttle body. When installing the new one you will want to move the throttle and watch that is turns the TPS.

 

I pulled the connector and it looked clean and dry. Don't have any di-grease handy as the parts store in my little town is closed till Monday. I'll wait until then to go any further.

Thanks for the help. I'll update the first of the week. I'm kinda excited though because if this one way or the other addresses my idling issues, I would of made huge strides in getting this truck on the road!

 

When you get the tps, get a new throttle body gasket too!

 

I'm trying, I really am...but

Changed the TPS and it fixed my idling and other obvious performance issues. Had to punt for a few days because my timing light refused to work any longer, so got a new one.

Reran the KOEO and got an "all clear" from KOEO and CM. Checked timing advance operation per the code reader manual. Checked base timing and it's dead on.

Ran KOER and got code 311.

I've been reading on this code and the thermactor system, and I kinda understand, but I was wondering if there was a clear path for testing in order to address this issue? I'm a DIY kind of guy, not a professional anything, so "clear" is imperative!

Thanks

 

I would start with some rubber vacuum hose. Reach in behind the intake above the transmission dip stick past the PCV valve. Remove the plastic vacuum hose and connect the rubber. Look at the plastic color and find it on the solenoids. Connect the other end of rubber hose there.

Of course this is if the air pump is operating.

 

Explain? Are you suggesting this vacuum hose is a common point of failure? I'm happy enough to do it, but I just want to understand why I'm doing it.

 

The plastic hoses do not last forever. The split and/or break when they get brittle with age.

After splicing my thermactor plastic spaghetti vacuum hose a year ago I finally took a half a day and replaced all the plastic hoses with rubber and the engine runs better. I have seen comments the plastic is no longer available. I used wiring numbers to label the hoses. Took a picture of the hood vacuum hose sticker, printed it and wrote the hose number on the picture for future reference.