I was just thinking how he could have MAF on a '93 when Ford didn't start using it until late in '94..

 

I pulled the IAC from the throttle body and cranked up the engine. Well the engine ran so loud I was afraid it would start fire . It sounded like the RPM was real high when idle. I drove the truck several yards and applied the brake real hard several times, and the engine did not stall like it did with the IAC on. Does this imply the IAC is bad?

 

Most driveability problems with speed density EFI can be traced back to the MAP sensor, if it hasn't been tested or replaced i would start there..

 

From what you describe above.........Good chance the TPS is shot, and causing the stalling problem. I had the same problem last fall with my '92, replaced the TPS and the stalling problem went away.
It was stalling on occasion at a full dead stop, but would re-start right up.

Your other post, with removing the IAC, what you were doing was sucking in air straight into the intake, that's like a super vacuum leak, or sticking a screwdriver in the throttle plate to hold them open, yea......it's going to race up the engine real quick

The bad thing about replacing the TPS, is you need to pull the TB off the upper intake to replace it. It's mounted on the bottom of the throttle plate shaft with 2 screws. What you might find, and I have in the pass.......is a hole in the TB gasket to the upper intake, and this could cause other vacuum leak type problems.

What gman is saying too, is the MAP could be causing problems, but in my experiences, if the MAP is not working correctly, the engine will not start, as it gets a vacuum reading from the upper intake, if no vacuum is being read, the ECU will shut down the fuel pump, and you'll get a "no start". To "by-pass" this, or trouble-shoot the MAP, is to use starting fluid at the TB, if the engine will start/run, then the MAP is shot. Also, read the Link that I posted, and there are some tests that can be preformed on the TPS and the MAP.

I had a busy week last week with the day job, so just getting back to your post on this

 

Clean the IAC and try again. They load up with carbon and stick, common problem. jim

 

Thank you all for the valuable input!

I replaced the IAC, TPS in the last couple of days. The idle seems to be fine(RPM on the low side though, I guess). However, the van still stalls!

I could drive the van fine as long as I "baby" the brake pedal, i.e., feather the brake pedal before the full stop. Otherwise the van would stall most of the time when coming to stops. It also stalls quite a bit in Reverse, which is similar the the problem another member reproted in the following threa:

https://www.ford-trucks.com/forums/1...ive-fixed.html

That thread says that for '96~'98 E4OD transmissions the filter could get loose and cause stalling problems. I am wondering does the same apply to '93?

In a different thread, another member who had the same problem said that his alternator went out and was not able to provide enough power to keep that engine running. How do I check the alternator?


UPDATE: I just had a friend who used to be working in a garage take a look at the truck. He immediately found out that the truck ran much better when the blower was turned off. So he thought it is more likely an electrical problem. We did a quick test on the alternator: the battery registers 12.5V and the alternator registers 13.8V. The alternator reading will drop momentarily when gear was engaged but would return to 13.8V shortly after and the reading never dropped below 13.5V. Does this mean the alternator is working properly? Next I pulled the ignition coil and measured the resistance and got 0.6 Ohm that is within the range so I assumed the coil is in working order as well. Then he said sometimes a bad ECU can make the van run rough which reminded me that I read a thread on this forum that says it is not uncommon for the capacitors on the ECU to go bad. So I pulled the ECU right away and cracked it open. Sure enough all the 3 capacitors had real bad leaking. Hopefully we've nailed my problem and this would be the last thing I change on the van for a while.

 

Good Call on Checking the ECU

Yes, been there and had to replace the ECU on my '92.

Some have replaced just the capacitors, but I kind of like the idea of a 're-man'ed' unit, that's been cleaned and tested and re-flashed from the factory.

Keep in mind, that there are several ECU's that will fit in your van, But, make sure the code numbers match up to what you have now.

Also, the E4OD is controlled by ECU in this era and a lot of the problems you have been having could relate back to the ECU's condition. The brake light switch is tied into the ECU to control the E4OD down shifting when braking/stopping.

If you have Autozone in your area? You could order the ECU thru them, and save the core charge over the counter. The core charge on these units is about the same price of the re-man unit, about $100.

Side note on your other testing, the voltage output of the alternator -
Seams that your alternator is with in range of output, but the battery is on the low side.
I just had this similar problem, and a couple of time I had no power for starting (no juice from the battery) dome light would go out, ect.....
Checked the battery terminal, it was tight, tapped on it, and the juice was back on........ended up cutting off the OEM battery terminal, and found that the copper wires were very corroded inside the crimped terminal, like in very black corroded. I went with the stainless steel clamps, and crimped on new copper connectors, and solved that problem, and yes, I did both positive and negative terminals, short end, replace the OEM battery terminals after 20+ years of wear and tear.

 

Sorry to bring back this old thread. I am happy to report that the truck passed emission test and has run very smoothly for the last couple months. I am hoping people with similar issues withe their trucks may benifit from reading what I learned when I fixed the problems.

As I reported earlier, the truck ran real rough when I first got it. It idled rough, was shuttering in idle and worst of all, it stalled every time put in reverse gear and/or came to stops.

I tried to pull the code but found no relevant codes. So I started with replacing spark plugs, wires, rotor and distributor. However, no improvement was noticed. Then I cleaned the IAC and throttle body. I found a bad vacuum leak when I was cleaning and replaced the line immediately. After that the truck idled a lot better but the stalling problem was still there. Then I replaced the TPS and ECU and the truck no longer stalls at stops! But in reverse the truck still stalls so I suspected that the transmission filter was loose. So I dropped the pan and replaced the filter and that seemed to have fixed the stalling problem.

So the take-away here is that the poor running was caused by a combination of a variety of many different problems. I hope this post will be useful to people run into similar issues.