Flat PCV Valve Hose

[littlet]

I've been searching for some ideas to fix some 1986 2.9l truck troubles. Great to have found this site. Current trouble is the vacuum hose from the pcv valve is sucked flat. Changed hose and pcv valve. Still the same. The truck runs fine cold but once it warms up it seems to stumble or miss and loses power.
Here is some of the history and things changed to date. A Few weeks ago truck at idle all of a sudden started running rough and smelled of gas.(rich) Would die. When it died you could here the fuel pump continuing to run. Got it home and changed the fuel pump relay. No go. Changed Fuel pump regulator. No Go. Read somewhere that the computer could be bad so changed that. That Fixed fuel pump running problem.
Ran codes and got o2 sensor error, and no knock detected. Changed o2 Sensor.
o2 code went away then had coolant temp sensor out of range, and idle out of range. Changed coolant temp sensor and throttle control sensor. Both those codes are now gone.
Current codes are KOEO 11, and continuous 18(spout Grounded)
KOER 25, no knock detected

Things changed:Cap, Rotor, Spark plugs, wires, pcv valve, coolant sensor, Ignition control module, engine control module, fuel pressure regulator. Also cleaned throttle body. The truck does have around 330,000 miles but would like to add some more miles to it.
Not sure what would make the vacuum hose be flat like that. But maybe this has something to do with it running rough. Hopefully someone can point us in the right direction. Thanks

 

[srteach]

All the info I use to answer is based on the 4.0 engine, so your configuration may vary from mine on specific parts, but not on the general principle.

The Positive Crankcase Ventilation system pulls filtered air in (usually from the air intake), circulates that air through the crankcase to collect (1 gasses that get past the piston rings and (2 vapor from the oil system, and pulls it past the PCV valve (a one way flow check valve) and into the intake to burn off the collected gasses. A collapsed hose indicates air not coming into the crankcase, or the PCV valve will not open.

First off, does the hose reshape itself when the engine is off? If so, pull the PCV valve (hose attached) out of its' mounting hole with the engine running to see if there is air being sucked into the valve and to see if the hose reshapes itself. There should be air being sucked in and it should be enough air to let the hose reshape itself. If not, replace the PCV valve.

If the hose reshapes itself, you have a restriction or blockage in the air supply for the PCV system. There is (or should be) a hose from the air intake to the oil fill tube of the valve cover. Check that hose for air flow. If there isn't a tube, there should be filtered source.
Does it run better with the air filter off or the intake open? If yes, the problem could be with the intake.

However you look at it, the engine is starving for air and running rich. You indicated that in your post. Check everything in the intake system (filters, clear flow intake valves) to find it.

Now that I think of it, start at the hose to the oil fill tube. Pull that off to see if the PCV hose reshapes itself. If so, the problem is in the intake system, not the PCV system. You should have vacuum at the open end of that hose (put finger over the end to test). Check the air filter, it can cause all the problems you are seeing.

Post what you find here so others can learn, too. PM me if you need more specific help