test with propane showed nothing. the engine idle did not change one bit no matter where the propane was released.

Now what?

none of the local shops have a smoke machine. How do I find one?

 

Running a very rich mixture at times causing a rough idle should be noticeable at the exhaust outlet on the drive. If it is going the other way, lean, than the exhaust pipe should be very clean. Check your pids for rich or lean answers. Then suspect your O2's or a bad injector. Conditions of some spark plugs should answer some questions and switching injectors would over time. Look for crud on injector inlet screens.

 

put my scanner on the truck. Watching the O2 readings at .025 with a good idle. all of the sudden it goes to .87 and idles like crap. does that for a bit then idle cleans up and it drops back to .025.

Idle can be good, then bad, then good again. Logic says that if this were a vacuum leak, it would do it cold then get better the more the engine warmed up and would not go back and forth.

This seem (tonight anyway) like a computer or sensor issue. I did note that the bank 1 and bank 2 while not exactly the same did track together.

this is driving me nuts

 

Ok, so today the computer gave me some new codes P1131 and P1151. Does this confirm the O2 sensor is bad?

 

O2 sensors replaced and problem is 90% better. There is still a random rough idle that comes and goes. The duration can be as short as a stop light or much longer.

Since it can come and leave during the time of a read light, I am thinking some computer control that starts and stops.

any ideas?

 

I take it U reset your Puter and it will take some time to relearn, give a tank full ? U may need to pull the tank and fuel pump to iron it out ? It's at that time frame. Did U watch your engine temp Pids and Air temp pids?

 

air and water temp and flow seemed ok while I was watching. To be honest, I don't think I reset the computer. Will do that tonight and see what it does.

 

reset computer did nothing

 

Since UR fuel system is switching back and forth and the O2's are responding I would Look to the intake PIDs first and watch them closely. U naturally immediately change the graphs as U give it gas and let off. At idle the change should be minimal. Same with the throttle opening and the graph for ign timing. Also the reset will mean all the tests will have to run, this will consume most of the morning driving it. Are you convinced it is not fuel/injector system related? Is it possible a couple are simply slightly leaking. Make sure U have the completion of the EVAP tests in the I/M.

 

Ok, so yesterday it was on a good spell when I stopped at a light. After 15 to 20 seconds of perfect idle the roughness hits. bouncing and shaking. Green light and I take off (runs great off idle). Stop at next light and it is perfect. It comes and goes just that random.

 

Ok John... It might be a faulty COP... Mine would not throw a code but it would still mis-fire... after like 2 years of bouncing and shaking when coming to a stop or slow acceleration... Check out my last post on the following...

https://www.f150online.com/forums/v8...sfiring-3.html

It's worth a try.

 

Thanks for the suggestion, not sure that is my issue. Mine runs off idle great, just a rough idle when the weather is cold.

 

Ok went to another shop. Now the idea is that the computer may be bad. This shop says they have a service to send it for testing for $100 and the service will call with a estimate for a repair.

I see Autozone and others have rebuilt computers for 200 to 300 (plus $100 to program at Ford Dealer).

What does the forum think? Test and repair or replace and reprogram?