My 86 ranger has the 2.9 and automatic. I recently put in a new oxygen sensor and it made a lot of difference.(not all for the best) The truck starts faster and overall runs great compared to a while back. However it has developed a random loading up problem. I will start it in the morning and It will run great for a while. When it gets part of the way warmed up, the motor will suddenly start to stumble and almost die. If I try to fight it and keep driving, the only way to get it to go is to give it a good portion of throttle and it will take off. But as soon as I decelorate, it will start stumbling again. Most of the time it will go away if I just pull over, put it in neutral, and wait. It will cough and sputter usually for 10 sec or so and it will suddenly spring back to life and run great the rest of the trip. But as soon as I park it for a few minutes and get back in, I have to repeat the whole thing over again. THe last time I drove the truck I had to pull over, and it sputtered for more than five minutes blowing out extremely rich exhaust untile it finaly ran good again. Other than this problem the new sensor has the truck running better than I have ever heard it run before. What may be causing this random loading up? Where should I look first? Any help would be great, Thanks

 

Well it could be a number of things & I might begin by pulling the vacuum hose off the fuel pressure regulator & see if it's wet with fuel inside.

 

I pulled the vacuum hose off of the fuel pressure regulator and it didnt look as if it had any raw gas in it. It did faintly smell of gas though. The other larger hose however, which I believe is a drain hose, had a good portion of gas in it.

 

There is a part in between the passenger inner fender and the air filter box that has a electical plug and 2 plastic hoses on the bottom. One hose runs to a threaded in vacuum port into the intake next to the throttle body, and the other goes to what looks like a diaphram canister that is under the throttle body. Whenever I shut off the motor, I can hear vacuum running either in or out of this part. It is fairly loud so I have a feeling it isnt supposed to do this. Could this be somthing that would cause some issues? It has a little cap on it that has a part# E53E-9J459-AA