Quality of the spark may be a problem as well.
I just had to replace my distibutor. Hasn't run that well for over 6 month. Rough idle and stalling. After the distributor, TFI, and Pick-up coil were replaced, the truck runs like new and has a lot more pep.
TFI and Pick-up are both pretty hard to diagnose until they fail. Found a Ford TSB that indicated that a faulty distributor / pick-up coil can contribute to irratic timing, poor running, and stalling. The diagnostic involved using a scope and analyzing the quality of the spark. A slight timing advance once per crank revolution is enough to cause the problem. ECA is pretty picky about the quality of the signal that it recieves from the TFI module.

 

I did pull two plugs, they were slightly worn but looked just as they should. All of those parts I've replaced within 10k miles, including battery cables last year.

 

I have a similar problem on a 1989 F-150/ 5.0 with 5 speed. Intermittently the truck will stall when coming to a stop. It appears the idle hunts up and down or just goes too low and truck dies. I have swapped O2 sensor, plugs and cap/rotor. Interestingly enough when I unplug the MAP sensor the truck runs like crap initially, then when warm it runs fine and hasn't stalled. I bought a new MAP sensor and it still stalls. I have replaced the IAC valve and was wondering if the ground could be bad. It appears that the IAC and injectors and just about every other sensor gets its ground thru the EEC. I found 864 ohms to ground and was wondering if anyone else has found or tried this. Thats seems like a lot of resistance to me, but when the MAP sensor is unplugged the truck runs find after warmup. I figured the truck probably would not run well if this was not the designed resistance to ground. The catalytic converter has never been replaced but then we still get back to when the MAP sensor is unplugged it runs fine except Idle speed is slightly higher at 1000 rpm. Any guru's have any ideas? By the way, the filters have been replaced.

 

Hey folks, can we go back to Fuel Injection 101?
Both sides of the throttle valve must be cleaned with carb cleaner twice a year.

 

My 86 302 efi had this problem and wasn't throwing codes at first,and Me and my mechanic were going over it tryed all the stuff mentioned in above posts and it wasn't untill my last test ride that it coughed one up it turn out to be the sensor for the EGR valve sticking replaced that and no more stalling when I come to a stop.

 

Thanks for the info. I will check into these things.

 

I've now noticed that my fairly new cap and rotor (with brass contacts) get carboned up, and that makes it worse. In the spring I'll put new plugs, cap, and rotor on there, wires are newer and should be ok.

 

Check the vacuum at the Map sensor. If it is 17 or less at ilde you have a problem in the engine.

 

The first thing I would say to do is pull the codes both not-running and runing. I had the same problem due to a defective ACT and an out of range O2 sensor. If that o2 sensor is out of whack on the EEC-IV, you are in for a NIGHTMARE (trust me...I'm just coming out of a in truck rebuild situation with electrical sensor hell after putting it back together)> Also, disconnect your spout connector and check your timing. It's supposed to be at 10BTC according the the radiator plalte but my scanner was calling for 20 BTC. Anyway, get to that point and give me a shout back. Lastly, disconnect your battery and pull your ECM out from under the dash(almost by gas pedal)...take off the wiring harness, clean it up with a q-tip and put it back. Be prepared for some headaches putting it back togerther...check every harness plug you have, clean them and dielectic them. rescan and see what you have....good luck.If you need schematics, let me know.

 

I had a similar problem with an 86 f150 (5.0). It was the injectors. They are expensive so do all of the other stuff listed above first and if all else fails start testing injectors, although I suggest replacing them all at once

 

hey, about your stalling problem....
Do you have cruise control?
if you do, does it work all the time, some time, or never?

If the cruise does not work i got your answer, but i wont waste time if it does work.

later.....

 

Hey nickmobile67,
I have a similar problem, did you ever find what your problem was?
Thanks

 

Hey,

Most likly it is the VSS sensor. (vehical speed sensor) It is located either at the tail end of the tranny or on the transfer case. it is a very simple working sensor. it uses a rotating magnet disk that makes and break a magnetic curcuit. the ECM needs to know how fast the truck is going when you are down shifting.

If your cruise control acts up too, it is a very good indication that this sensor is shagged.

When you are down shifting, to come to a stop, the throttle is closed and the engine revs up because you are using the engine to slow down. If the ECM does not see that the truck is still moving, then it only sees that the engine is reving high and the throttle is closed. therefore the ECM slams the air bypass valve shut to try and slow down the RPM. Once you put your clutch in and the wheel no longer drive the engine, it stalls out.

this sensors can somtimes be a pain to set up. If you change it, and over tighten it, it will pinch the magnetic disk. if the disk is pinched it cant move and therefore wont transmit the speed to the ECM

This will also only happen with 5spd trannys.

hope this helps.

 

This only only happens to trucks newer then 1986 our trucks don't use a VSS.
Glenn

 

And my cruise control does not work either