91 ford aerostart will start but not run

[ultrarunner]

When I worked in the family car business this problem was almost always a problem with the ignition switch and once in a while a bad ballast resistor in the coil circuit.

[Tig]

I don't know the Aerostars but if this was an old Chrysler product it would be the ballast resistor. I think Ultrarunner is onto something.

[WTA]

What ballast resistor do people keep talking about? I never saw or heard of one on a 91 model ford. I highly suggest at least trying the reset procedure I already posted about before spending any money on parts. I was a ford Mechanic from 95 till two years ago and have a little experience on these things. I still work on Fords only here in addition to my gun business because all of my tools are for fords and they are the easiest to diagnose for me. I mostly do antiques now though. Theres something about working on an original model A or a 65 mustang that is very relaxing after spending too much time diagnosing computer problems.
I also ran a million miles on my 91 F-150. Different engine, same exact computer system. EEC-4's are simple but frustrating till you learn the ins and outs of what makes them tick.

When that battery goes dead, or below 5 volts the memory is erased. All it has to do is relearn it normally. If that IAC on yours is dirty, and it probably is, it can't do it on it's own and needs a little help.

FWIW, if the ignition switch were bad, it would not start then die. It would either not turn over at all or not crank up at all.

[Soundguy]

Will try all these ideas as soon as I get some time off work.

As most of you know I moonlight in the entertainment industry.. and I've been pulling doubles since christmas and will be doing so till the 2nd or 3rd.

thanks

Soundguy

Originally Posted by WTA

Just get in it, set the parking brake hard, step on the foot brake, restart the engine and then immediately put it in gear and

feather the gas pedal up to about 1000 RPM and hold it there for a minute or so. (ONLY FEATHER THE GAS IF YOU HAVE TO)

It should automaticaly go to IN GEAR mode for rpm which opens the IAC more anyway but if it doesn't want to then idle it up manually before it dies and slowly come off it as it picks up itself.

You have to put it in gear and up the rpm within 3-5 seconds if I remember right or this doesn't work.

Keep it in gear for at least 10 minutes idling with the AC off and not doing anything else. It should relearn fairly quick but 10 minutes is minimum. Then drive it around the neighborhood so it can relearn everything else. It will probably run weird for 20-30 miles or so.

If the battery went completely dead this is probably all it is. It happens sometimes.

All 91's that I've ever seen are EEC-4 computers. This is the standard way to fast learn the idle again after a dead battery or a computer swap.

It should pick it up itself but it probably has a filthy IAC solonoid. If you have the IAC that has two screws attaching the solonoid to the actual valve you can take it off the throttle body first, then seperate the solonoid from the valve and spray some foamy window cleaner in the valve then let it sit a couple minutes. Then rinse good with hot water. Repeat this untill it's clean.

DO NOT use carb or brake cleaner. Unless you want to be cleaning it a lot more often. It will take off the anti stick coating on the inside of it.

eec-4 obd-1 and obd-2 will all set codes when the engine is first started and cold. Not always though. Usually when it doesn't on an eec4 then it's just a failure to control idle problem because it's memory has dumped and needs to relearn. It doesn't know how much to tell the iac to open till it's too late. This rarely sets a code because it tried but the engine died before it got there. Now if there were an electronic fault then it will set a code.

[wrenchturner]

Once upon a time I worked on a van like this that would not run but if you kept the switch in the crank position it would continue to run. As soon as you returned to the run position it would quit. Two gentlemen drove this van 35 miles to my shop. As one drove the other held the switch in the crank position. Long story short, after trouble shooting, the problem was the ignition module.

[Soundguy]

Interesting....

I have not had time to continue working on it with the low temps.. but DO remember that it would stay running if I held the key in crank for a second after letting up.. vs dieing as i let the key off.... HMMMMMMM

soundguy