Hi all! I really need some ideas or even better a solution. Bare with me, this will be kind of long.
1992 Ford E350 7.5L automatic w/over drive cutaway cab, Class C motorhome.
This thing sat for over 10 years before I was blessed with it. First off, I dropped the gas tank and had a radiator shop get the tar all cleaned out of it and epoxy coated the insides. Flushed the fuel lines.
New fuels pumps ( in tank and high pressure ), New plugs, wires, cap and rotor. The Thermactor air pump was frozen solid, so I deleted that system.
New fuel and battery, it cranked up and after a while it would even idle, but very badly. Tons of black smoke out the tail pipe.
I hooked up a vacuum gauge and fuel pressure gauge. Fuel pressure was good, but vac was horrible. So I started checking vacuum hoses and plastic lines. Some were brittle and some hard plastic lines were cracked or broken, so I replaced every one with new hose only, no more plastic lines.
Still had the same problem, until I found the MAP sensor up on the cowl (of all places) was leaking vacuum. replaced the sensor and it purred like a kitten....at idle. Gave her a test spin. Hesitation off idle, couldn't get above 30 MPH without it backfiring. Step on the gas and only got that lonesome boggy howl.
Replaced the fuel injectors and pressure regulator. Also cleaned the fuel rails real good. She seemed a bit happier, but still no power.
I was getting some strange random error codes dealing mainly with the evap and EGR, but some off the wall ones too. New EGR position sensor, Traced wires, checked voltages, etc. Everything was good. So eventually I gave in and replaced the ECM with a reman.
The codes stabilized to just the EGR. I had tested the EGR valve with a vacuum pump and the diaphragm is good. Eventually found out it matters which hose barb you connect the source vacuum and EGR valve vacuum to. Get it backwards and it doesn't work right and causes a small vacuum leak. So I swapped the hoses on the EGR vacuum solenoid and things perked up pretty good. It ran well enough, that I was able to drive it about 5 miles and get a state inspection and return home.
The next day my wife wanted to take a ride in the beast and I was back to square one. It ran sooooo bad we thought we might have to have it towed home, but we made it.
Over the next few weeks I replaced the TPS, the Charge Air Temp Sensor, Both engine temp sensors, Yanked the Cat and made a test pipe and replaced the ignition module. I even ran it with the Cat off, but it made no difference.
Over several test drives, it sometimes starts out really well, but craters after a few miles. Sometimes it craters before I get out of the driveway.
Fuel pressure is good, about 34psi cold startup, then 42 to 45 after it warms a little and I goose it a few times. Vac is at 20 at first startup and reacts as it should when rev'd up, held then released.
Today I replaced the ignition coil, no difference at all.
Then I pulled the distributor and replaced the hall sensor. New sensor wouldn't even start the engine, so I put the old one back in it and it cranked right up.
The parts manager at a local parts house spent 20+ years as a Ford tech, I have taken up a lot of his time trying to help me diagnose this thing, and nothing has helped.
I have searched a LOT of forums for similar threads and every one I find cannot find an answer, or they just stop posting and an answer is never revealed.
HELP! Please

 

oh, and new O2 sensor too

 

The ignition module is a strong possibility, unless I missed it that may be one of the few items you have not changed yet.

 

How many miles on it? Check for timing chain slack?

 

Yep, I replaced that too.

 

It only has 24k miles. I had a friend watch the ign rotor while I was underneath turning the crank by hand. It seems the chain is ok.

 

You know....the ignition module I bought was a cheap aftermarket. Perhaps I should try and find a Motorcraft one

 

Yes.. all these aftermarket electronic bits(like your hall effect sensor) have a terrible reliability/DOA record. Are you getting a code for an erratic PIP signal? That is what the Hall sensor generates and what the TFI module modifies to achieve ignition advance, so both of these are top of the list for problems like you have.

 

The Only code I get is code 34
Sorry, I lied. Also get a code 81

 

Code 81.. secondary air injection diverter solenoid failure.
That is interesting. The diverter valve switches air from upstream at the engine to downstream at the cat once the engine reaches operating temp. If Air is not being divereted because the valve or it's control solenoid(TAD) is broken this will seriously mess up the O2 sensor readings. The solenoids are usually right next to the ignition coil.

 

"The Thermactor air pump was frozen solid, so I deleted that system."

 

Have you checked the ignition timing yet?
Is the vacuum advance working?
Yes, get a Motorcraft ignition module
I doubt that is your problem
So, is the cat still off or straight piped?
Was the cat not broken up?
If it was, there is a possibility that the muffler is full of cat substrate
Do a vacuum test for plugged exhaust
Drive it around with a fuel pressure gauge taped to the windshield
Good luck

 

Yeah, the 81 code was expected. No cat at the moment, no air injection pump. I am a little curious about the muffler and plan to replace it anyway because the outlet pipe is wiggly. So something is loose there.
I have the doghouse out and have fuel pressure and vacuum gauges connected all the time while trying to figure this out. They just sit on the rear of the engine where I can monitor them all the time. Fuel pressure stays in the 40's all the time while trying to drive it. Vacuum, of course, drops when on the throttle, but recovers well when I let up while driving.

I noticed a small loud speaker under the hood near the master cylinder. Would this be a sign of an aftermarket alarm system? The wires to it had already been cut and I have not seen any unusual electronics under the dash, but I am old and don't really know what I am looking at under the dash anyways. (not there is a whole lot of 'under the dash' in a van to speak of ) Could that play a part in this? There are a few places where Scotchlocks have been used to splice in some new wires, but not on the wires to ecm or sensors.

I keep looking around the corner expecting to catch Rod Serling talking trash about me

 

This is a VERY low budget project, and I have already spent way more $ that I had hoped, but I am only going to give this a few more weeks and then I am considering getting a carburetor, intake and aftermarket distributor and doing away with the ecm and it's mess of sensors and wires. I live in Texas, and since this is a 1992, emissions testing is not required on this old of a vehicle anyways.
But I am willing to try and work this out, if nothing else but to post my findings for anyone else out there with similar problems.

I REALLY do appreciate all the help from all you folks. Some of the things suggested, I have already done. That helps me though. It makes me feel better that I have someone else thinking the same thing as me and I have not gone completely off my rocker.

So, thank you! Keep the ideas coming! ... please

 

Ok.. all associated plumbing was removed and all points where it attached to the engine or exhaust was plugged? There can be no exhaust leaks upstream of the O2 sensor.

If it's a thumbs up to all that I say go back to the ignition module and hall sensor.