Knightmayre have you checked very closely for vacuum leaks? The most common place on a 302 for a leak is at the rear of the upper intake where it bolts to the lower intake. If you remove the engine cover it's very easy to get at. Take some spray carb cleaner such as Carb-Medic and, with the engine running, aim it at the intake manifold where the upper and lower halves join. If the idle changes at all you've found your leak. A bad vacuum leak can cause a high idle as well as a rich condition due to low vacuum to the MAP sensor.
If that's not the problem I think the next thing to try might be a new PCM. I've seen them cause similar problems before. If you can find another van the same and swap PCMs that would be an easy thing to try. I just hate telling you to go buy a new one and then find it doesn't fix it

 

Dave:

I've bought everything else so far- nothing to lose

Am sure that the vac line to the MAP sensor went further back towards the transmission, but might be getting confused.

I'll spray the manifold tomorrow & see if anything changes.
Think I know someone who might let me borrow a PCM to try too.

Thanks for all your help, but it's getting to the point where I might have been better actually taking it to *gasp* a dealer. (Who are all snooty as hell round here if your vehicle isn't nice n new n shiny- how dare you expect us to fix an 88).
Just makes me all the more determined to find & fix her!

 

Just got through a whole can

Sprayed all around where the upper & lower manifolds join, and on everything that even remotely resembled a vac line.

Oh, and to see if it was the TFI module, I sprayed the hell out of it with component freezer. I also unplugged the coolant temperature sensor just to see.

Still no joy

 

It may be a long shot, but someone else also mentioned checking your Ignition Control Module. The majority of the time, they don't start showing any wear and tear until they're nice and hot. Try testing that, whether using a haynes manual or taking it off and taking it to someplace like Autozone, who can test it for ya. You've pretty much replaced everything else.

 

i have an 86 that had a similar problem after basically restoring the truck looking for this problem, i found a broken wire in my harrness. the truck would only act up when it was at operating temp. wire was barely touching together when i found it. spliced it together and been plowing ever since.

 

Have already done a fairly extensive wiggle test, more than once too.

Hopefully I'll have my hands on another PCM to try this week & see how it goes from there

 

How about going back thru this thread and collecting all your symptoms, everything you've changed out, every test you've tried, and the exact results of each so we have all the most current info to look at. Also, include the vehicle type & engine.

I don't see the results of the fuel pressure test or the pulse-width test... Did you ever eliminate a leaking injector as a possibility?

 

Can't find anyone local with a guage, so no fuel pressure readings (all 4 local garages say they haven't got one, that's why I don't use the local garages!).
I haven't scoped the injector pulse width yet, as I have no data to compare my results with.
To see if I had a stuck injector, I pulled the main fuel pump relay then left the ignition on for a while as I wiggled the injector harness & connectors. I then checked to see if there was still pressure in the rail- I was assuming that if an injector harness was shorting to ground then it would open while it sat there with the key on and the fuel pump off & relieve the fuel pressure.

OK, to recap...

88 E150 302

On a cold-start, engine starts right away although as soon as it does, CE illuminates & idle goes on the verge of stalling. As it warms up, CE light will go out momentarily along with an elevated idle. Takes about 5 - 10 minutes for the CE light to go out permanently, then the idle is high enough to be able to pull away... will do 40mph on the flat without touching the gas.

Vehicle floods easily, usually when pulling away or when changing gear (with the shifter ie P to D). I have to put it in D, sit there while she chokes (black smoke spews from exhaust) then she'll clear & I'll be OK, as long as I pull away without touching the gas- if I do, she'll choke & die. Makes manuevering (sp) really hard when you have to wait while changing gear. If she floods, is a &*&^ to restart without waiting.

6(!) mpg.

New FPR, TPS, IAC, O2 sensor, plugs, air filter.
Cleaned Throttle Body & as much of the intake as poss & ACT sensor.
Tried known good MAP sensors.
Tried running with EGR & PCV valve disconnected.
Sprayed every vac line, upper & lower intake manifolds to check for leaks.
Timing redone by ear as I still can't find the timing marks, and retarded little by little until it stopped pinking under acceleration.
Battery removed overnight to stop any adaptive learning.

I know I still need to get the base timing right, but am sure she's close enough. Not convinced it's the PCM either, but I'll find out Saturday as I've found someone willing to let me use their van as a testbed for the day. Intend to go back over the harness again too- I haven't had a chance to look at the connector to the PCM as I don't know how watertight they are on this model.

This has got me down in the dumps in a big way!

 

I had the same prob. with my 92 f150 4.9. It was fine untill it warmed up and then would stall. Pull the control Module off and any good parts store will check it for you at no cost.

 

OK I didn't see any fuel pump tests in the list, so find out how much current each one is pulling (the in-tank pumps and the frame-mounted one) and buy a fuel pressure gauge at Sears - they're only ~$20 IIRC. You also REALLY need to shoot it with a timing light - any shop has one, but if they won't let you use it or check your timing free for you, Sears sells those for ~$30. Also, change the fuel filters - there may be one inside the tank select valve inside the frame rail near the rear axle, and that valve might also be the cause of the problem. The Haynes manual tells how it works and how to check it.

I'm going to sleep.

 

Thanks guys!

I have a timing light- I just can't find the marks! (and Sears is over 60 miles away from me- I live in the boonies)

The Haynes manual for the full size vans is terrible- doesn't even have a list of codes or anything, and as for the main fuel filter all it says is "... designed to last the life of the vehicle and should not need servicing". Doesn't mention a tank select valve at all- in fact it omits a whole hell of a lot when dealing with the EFI system. If it does deign to mention something, then it's usually along the lines of "take it to a Ford dealer".

I'll post again at the weekend after I've had a chance to play with the other vans computer.

 

oh come on,no service needed ,what does it do with all the crud it catches ,every once in a while spit it back in the tank? lol

 

LOL! I know, I couldn't believe it myself!

I guess Ford secretly developed a magic everlasting fuel filter.

 

Yup, you were right- I had changed the injectors & started her back up, only to have the same problems. I don't know why I didn't do it before, but after she wouldn't start after she'd ran for about 5 minutes, I searched & searched for that sensor, unplugged it & she started right back up.

New sensor & she now runs a treat- gave me 6mpg before, now gives me 12 CE light now stays on, but I'll fix that later!