93 CPI Surge and Idle issues

Ok, I'm going to give you the run down. It might take a bit cause I want to give you as much info as I can.

I am working on a 93 s10 Blazer 4WD 4.3 CPI auto. Now, this is the second engine and I am only at 125000miles right now. The first one spun two bearings and destroyed the crankshaft. It also got a new fuel filter and pump at this time. So new bearsings and crankshaft and it went only 5000 more miles and through a rod.

Thing sits for 3 to 4 years before I can get back to it.

Instead of messing with that engine I picked up an engine from a yard out of an astro van(#2). CPI, same year, i think. with 60,000 miles. Its from the north east and the van rusted out before it could damage itself.

Swapped that in and used the intake and everything off the original engine. New plugs and wires. New waterpump. New distributer cap

While I was at I tried to put on Headman headers. Big mistake, I will never do it again and suggest that you do the same. They will be cut out. The do not tie into the stock system like I was told they would. Had to be moddified to even let the sensors fit. No o2 sensor bung. You cant even get bolts into all the holes without modifing it! Forced me to cut the wire and relocate a knocksenor. And now I cant even get the inspection plate on the bottom of the transsmission (auto). So it is sitting with the headers being the only exhaust system till I remove them and undo all this crap. It will not be driven to all of this is fixed.

Drained the fuel tank. It was completely full when it died and is the proper way to store a tank I am told. So that was drained and has 5 gallons of fresh gas in it now.

This one runs and has 80psi of oil pressure at idle. Far more than the last engine (35idle-50psi at speed)

But it wasnt firing on all cylenders so I checked the whole ingintions system to make sure that it all worked properly. I dont know if the time is 100% correct anymore though now that I missed with it. Fuel pressure at this point was 62psi with the key on and stayed steady. 56psi when cranking the eninge. Turns out that the spider was not firing to all the "legs".

Swapped in the spider unit from the astro. It had a leaky regulator and "legs" so I swapped those from the original unit and now it runs. I check visually for leaks but did not check the fuel pressure again.

All of this finally brings us to the problem at hand...

It will surge at idle and then it dies. If you give the slightest amount of gas, enough to run at 1000rpm it is fine and completly smooth.
If you disconnect the vent at the top of the intake manifold that goes to the vent on the valve cover it will surge but it will keep running and not die.
Still open after headers an the 02 sensor is there for the ecm to see but not in the exhaust system.

What Diagnostic Trouble Codes are presently being displayed?
You should have a Check Engine light for the "cold" O2 sensor. Instead of the computer adjusting air/fuel on the O2 sensor input, it's in limp home mode where it'll just get you home from the MAP sensor, TPS & ignition module input.
Where did you relocate the knock sensor? Was the stock wiring connector still in good shape?
Yep, I'd cut the headers off it too.

The driverside knocksensor got moved to a spot farther up on the head in the hole right above where it was ment to go and the one that was on the back of the engine is now in the same spot (above the water temp) on the other head. Possible source of the problem?

Umm the only code that it ever gave me was code 12, i think. My repair manual says that is the code you will get simple from reading the codes with the key on.

The o2 sensor is tucked up in some of the metal shelding that is under the body to keep it off the ground and protect it for now. Would it be grounding out or doing something funny because of that? Or because it isnt getting any exhaust flow?

Would it help to reset the ecm again? It sat without a battery the whole time it was dead, would that be part of the problem?

You should show a:
Code 13...O2 Sensor Circuit Open unless it's grounded.
Code 44....O2 Sensor Circuit/Lean Exhaust Indicated, due to low voltage/no hot exhaust present.

Of course there's the regular CPI problems like the sticking EGR valve and Idle Air Control valve.
The module in the distributor can mess up the idle when it goes bad too.

I had the module in the distributor checked out at autozone, so thats fine.

Would any of those codes even show up if the engine was only run at most 1 minute at a time? I havent run the engine long enough for it to warmup becuase it isnt running right

Good point, i think it has to get warm to get in closed loop.
Maybe if you let it run long enough to get warm, the computer can help determine the problem.

Because of my degree program it will be a couple weeks before I will have the time to get those headers off and put the stock ones back on. So what all would cause the computer to go into limp mode? And what should I look at when I have the time? Would the computer run like that anyway because of how long it went without power till it was able to go into the closed loop and relearn what the engine needs to run?

What would the ECM do, if saying where I tucked it up into the body it was grounded, the O2 sensor was only reading normal air and not exhaust? Would this cause the surging? And what might it do short term if it wasnt getting any signal at all from the 02 sensor?

Have you moved the ECM from it's stock location?
I believe the O2 sensor has a ground wire, signal wire and a power supply wire if it's a heated sensor but it has to see exhaust heat to function.
It's a thermocouple, creates tiny electrical current in direct proportion to the exhaust heat it's subjected to.

No, the ECM has not been moved. So would I be right in assuming that the surging problem could be the fact that the 02 sensor is not reciving any exhaust flow?