87 Bronco 2 surging, missing, and running fine, sometimes!

Help needed!

I can start up my 87 Bronco 2 XLT, with a 2.9 fuel injected V6 and it runs great, smooth and steady. That is, till the temperature of the engine warms up 5 or 6 miles maybe. Then it will start surging under load and missing like crazy. Now while driving and staying in drive, I can turn off the switch and immediately turn it back on and everything is fine, for another 2 to 3 miles. Then the symptoms start again. Sometimes I can press down the accellerator till it drops a gear and it will catch and run smoothly again, momentarily, then back to the surging again. When it's cruising straight and level, at a steady throttle and it starts missing you can feel the surge kind of come and fade like a cycle up and down. When this surging happens it shows signs of flooding. Black smoke from exhaust. It's like something that resets after a re-start but then goes haywire after a couple, or 3 minutes.

Checked my codes and got an 18 and 33. Egr not opening and spout connection.

Here's what I have done. Replaced Ignition Module, replaced distributor pick up module, and cleaned connections(no change). Replaced EGR vacumn switch. Checked and replaced most vacumn hoses and connections. Cleaned and checked EGR, (no change). Replaced MAP (no change) Replaced throttle position sensor (no change). Replaced air by-pass assembly (no change). Replaced engine temperature sensor, (no change). Checked fuel pressure 32 lbs and constant, running. Replaced fuel filter (no change). Replaced ECM (no Change). Cleaned throttle body (no change). Ran 2 cans of injector cleaner through it (no change). Checked vacumn and it shows 14lbs at idle.

Well as you can see I have tied up a tidy sum throwing parts at this thing and (no change).

Sure hope somebody has an answer here. This must be a common problem. Not only do I have this problem with this B2, but I have a second 87 B2 that I parked last year and it was doing the exact same thing!

How about it guys, jump in here and tell me what I'm missing! All ideas appreciated.

Thanks for any help.
Ron

Come on Guys!! Surely someone else has experianced this problem!

I did check the vacuum today and it was a steady 20lbs. Then the miss surge started and it fell to 12lbs during the episode and promply returned to 20 lbs when it cleared up again.

IDEAS???

Use a can of carb. cleaner and spray along the edges of the intake manifold and base of the throttle body. If you have a leak the engine should smooth out when the spray hits the leak. Check for leaking hoses to the intake.
Pull the vacuum line for the vacuum booster and put a bolt in it. If the engine smooths out buy a replacement vacuum booster.
I've had to buy a gasket for the throttle body and clean them before.

Use a can of carb. cleaner and spray along the edges of the intake manifold and base of the throttle body. If you have a leak the engine should smooth out when the spray hits the leak. Check for leaking hoses to the intake.
Pull the vacuum line for the vacuum booster and put a bolt in it. If the engine smooths out buy a replacement vacuum booster.
I've had to buy a gasket for the throttle body and clean them before.

Thanks for the reply, but sorry to say I've done all that and still no solutions. I really feel like the problem is something controlled by the ECM. As I said before, while driving and the problem occurs, I can cut the ignition switch off and immediatly back on, and I the B2 runs great for another 2 to 4 miles. Then it re-occurs. Also when cold it runs great till normal opperating temperature has been reached. No problems at all till the temperature indicator reaches normal, then it goes haywire!
Thanks
Ron

Check the connection in the ground wire that feeds the computer. This connector is very near the ground terminal at the battery. I found that I had a corroded connection which caused ubder voltages to and from the computer. This will cause the computer to "SEE" weird codes and cause the computer to try and compensate for the lost ground. The way I found this was my fuel pumps would not come in when I turned on the ignition. I know that you will think that this cannot be possible, but my "FLAG" was the fuel pumps, I have seen this cause so many issues that it you would think that the computer "MUST" be bad.

THERE IS A GOD!!!!

In a last ditch, desperation attempt, I went out this week, and bought another ECM for my BII. I pulled the recently replaced ECM, and intalled the new one.

With a prayer and and being very carefull not to get my hopes up, too much, I got in and started the engine. Sounded fine, but it is only after warm-up that the usually missing and sputtering started. So with great antisipation I waited till the temp hand got up to normal. Hey, it still sounded good! Could it be possible? After sufficent time for warm-up had pasted, the engine was still purring. I pulled it into gear and left my drive way. 30 miles later the engine was smooth as silk, and not even a miss. A great big smile crept across my face! Could I be mistaken? Could it be true? Not wanting to be too eager to proclaim victory over the curse, I took the BII home and let her set over night. This morning I went out and cranked her up. Guess what! Smooth as silk!!!!! I drove her around for a while and not even a hesitation!

Moral of the story? I don't know one, but I do know that, I will not ever again feel that replacement parts should be considered to be always good. Strange that the first replacement ECM would create the same problem code and symptoms as the original one, but it did.

Now if my neighbors will just forgive me for creating such a disturbance, with all my joyful bliss!!!!

Hope this helps someone else along the way. Just glad I didn't give up and call the crusher, although I did give it some serious consideration!!!

Thanks for everyone's input and attemts to help on this one!

Ron