My boy just bought a 1981 bronco 5.8 with EECIII. I spent 1/2 a day diagnosing the EEC and vac. lines that were messed up from years of abuse and lack of knowledge. I dusted off the EEC area in my old brain and dug out all my old info (books, vac. and electrical diagrams, testers). (Been with Ford since 1974 doing drivability). Any one need help or info let me know. I beleive in helping fellow enthusiasts, especially while this stuff is now fresh in my mind again. I have a digital camera. Norm in Calif.

 

Welcome norm!

I had a problem with the TCIL on our 96 Bronco e4od (see below thread).
It is ok now, but our local good guy mechanic said there is or was an intermittent short in the column or col/dash area that caused the fuse to blow and the TCIL to light up on it's own (Did NOT blink).
have any ideas on where the short may be? Some have suggested that the harness may have been positioned incorrectly when the Bronco was built.
Whadda thunk?
Be well!

 

I looked in a wiring diagram. The fuse #17 10 amp gives power to :electronic shift control swith if equiped, instrument cluster, warning chime module, and tcil switch. That might help if its a intermitent short. To come on the pcm grounds the circuit based on a fault or the return wire would have to be shorted to ground.If you turn the lite on wiggle all those areas and see if the fuse blows. If it came to my Dealership it would go to either trans or electrical. My specialty is drivability. Maybe this info can help. Norm.

 

Man you opened the door for a flood. I may be bothering you about a closed loop problem with my '89 302 Bronco. I changed the fuel filter last weekend but my E brake cables in back are stuck. I can't drive it to see if it is fixed until I get time to fix the cables.

 

Hey Norm here's one for you.I've got a 90 Bronco 302 AOD.Engine recently rebuilt.All stock except for comp cam(made for speed desity set up) and flat top pistons.Ever since the rebuild running real rich,like 8.5 mpg.I have checked and had all the sensors checked by mechanic.New ECT,MAP,EVR,EGR 02 sensor.It's like it's not going into closed loop.When I check the 02 voltage it doesn't cycle rich to lean it just stays at around .8 volts.If I unhook it from the connector it actually drops to about .7 volts.
Thanks,
Billy

 

Norm,
Thanks!!
update...No codes found.
Fuse was not blown; chimes and instr. panel lights were working. (I posted another inquiry here and stated that Mike our local mechanic said the #17 fuse was blown, but that was a mistake on my part; I called him later and he said he pulled the fuse, checked it and then replaced it.)
Mike, said the wiring was ok, not shorted anywhere along the path from the tcil through the steering column/PCM. It is as you stated an intermittent short in the strg col or under dash.
Tranny still shifts great and the LED is off now. It will light when I cancel OD.

So all is well today in jerseyland! .. for now..lol

Many thanks for looking it up Norm!

 

Billy hears a bunch off things to check. The older eec1v like yours needed to see operating temp to get into closed loop. Make sure you aren't to cool. The pcm loves to see at least 190. The ect should be around .5 volts. Check fuel pressure. about 30 psi, 40 psi with the regulator line off. Obvious things like timing set 10 deg. with the spout unplugged. Monitor hego while hooked up. If .8 - .9 creat large vac. leak like unpluging power booster, hego should drop lean well under .5. Mke sure the hego heater is gettung power. On a 3 wire hego, 1 is signal, the other are keypower and ground for the internal heater. The hego grounds to the exhaust. 4 wire hego's ground in the pcm. I don't think its a ground issue. Open hego grounds usually show 0 volts from the sensor. There is so much more. Give some of that a try. Norm. I almost forgot. I have seen the iat sensor get all coated up in the intake. Most won't show up in testing. Its best to look at them.

 

Thanks for the input.I checked the resistance on the ECT and it does change with engine temp and is in spec per the haynes manual.I will check the voltage signal.I assume .5 volts is hot.I did have a 180 thermastat and changed it to a 195.The mechanic who looked at it checked and cleaned the air charge sensor.I need to check it's out put,it's probably the only sensor I have'nt tested,but it is new.The 02 is a 4 wire and it is getting a voltage signal.If the o2 leans out with a vacuum leak where do I go from there?I have also checked the Fuel pressure regulator.The pressure is about 36 running and increases
when the vacuum line is disconnected.The diaphram will hold vacuum so it's not busted.The only other thing that puzzles me is when the key is off the fuel pressure bleeds off quickly.I have all new injectors.I know I'm reaching here but what about an intake leak at a cylinder port?The intake is under vacuum so I'm not sure it would leak into the crankcase.I also have an idle surge but only in gear,in park the idle smooths out.Thanks for your help as I am very worried about ruining a brand new engine.I can smell gas in the oil so it is running very rich.I have checked all the plugs and it does not seem to be isolated to any one cylinder they are all rich looking.I have put new wires etc.

Billy

 

The fuel leakdown is probably the fuel pump check valve inside the pump. If it was an injector you would have a momentary miss on that cylinder on startup. Are the injectors exactly the same . They make a ton of different injectors for all the hot rod mustang guys. Have you done a engine running test to see if the computer is happy. Is the mpg on the highway. If the hego leans out with a vac. leak, but stays high when running then the hego is ok and we have to keep looking. The hego harness on those runs right along the battery cable and I have seen many hego's sending out over a volt to the computer due to battery acid causing voltage migration to the hego circuit. It can be intermittent and more prone when damp. A good sign is acid around the battery and cables. If the truck passes a running test then the EEC is able to control the fuel circuits driving them rich and lean on command. Some times we have to apply some hard logic on problems like that and ask just what is different now than before. Those injectors, are they new ford units. I beleive 90 was the beginning of deposit resistant injectors so if you bought from ford they should be exact, if not they should be able to tell you "those are a new updated part #". Also remember motors need some break in before best mpg. The 180 to 195 should help. Is the map hose nice and open. Norm.

 

By an engine running test I assume you mean a code check with the engine running.It is not throwing any codes.I have had an intermittent egr problem.A code 33 was showing in memory codes and sometimes during running test.The egr will open with vacuum.I replaced the evr solenoid and the evp.If the egr is not opening would that cause it to run rich?It is not pinging under load.I did not replace the injectors initially after rebuilding the engine.When all these problems surfaced I bought a set of new mustang takeouts off the net.The strange thing is those suckers are pink.I bought them from 5.0 motorsports and the guy claims they are new mustang take offs.The engine is about a year old and has about 10k on it.Now my son is driving the truck a very short distance to school.Lots of stop and go driving.But still 8.5 mpg is bad.The oil is getting dirty quickly and smells of gas.Also,the mechanic who looked at it advanced the base timing to 19-20 degrees and it would'nt ping.The truck overall is just sluggish since the rebuild.I have a friend who swears I need to advance the distributor one tooth,but to me if you can set the timing this should'nt matter.Tomorrow I will check the 02 sensor again with a vacuum leak and see what it reads.I will also pull the codes again.If the truck is running rich shoud'nt the pcm set a code for it.It's almost like the pcm is out to lunch.I've been told it's rare for these things to go out.Thanks again for your help.

Billy