Runs Great when it's cold

[bowturkey]

92 ranger 4.0 runs great when it's cold under load, response or whatever. Go down te road 20 miles hr in 5th gear no bucking or anything . Once the teperature gets up to where it suppose to be it cut's out some times under a little load like it either loses gas or electric. It has to be somthing with when it gets warmed up and all the sensors and coumputer take over. I have changed some things nothing changed to this point vaccum seems to be ok. Has me stumped. Any body have a thought?

 

[Big Jim M]

Yeah, I've got an idea. What the hell are you doing in 5th gear at 20 mph? What the hell do you expect? That is REALLY hard on the rod bearings.
But to answer the cold versus hot question... when cold the timing is restricted to a minimum and not allowed to advance to where it will be when hot... ALSO the mixture is quite a bit richer when cold. So the combination of timing and mixture allows the engine to run when cold.. then when the engine heats up the MILAGE control of the computer kicks in and the engine runs much better at hiway speeds..
BUT at 20mph your ride should never be beyond 2ed gear..
Big JIm

 

[Fordisthebest30]

Yeah, I've got an idea. What the hell are you doing in 5th gear at 20 mph? What the hell do you expect? That is REALLY hard on the rod bearings.
But to answer the cold versus hot question... when cold the timing is restricted to a minimum and not allowed to advance to where it will be when hot... ALSO the mixture is quite a bit richer when cold. So the combination of timing and mixture allows the engine to run when cold.. then when the engine heats up the MILAGE control of the computer kicks in and the engine runs much better at hiway speeds..
BUT at 20mph your ride should never be beyond 2ed gear..
Big JIm

Dude That whole 5th gear, thing, i was thinking the same damn thing. my truck starts bucking when i put in fourth around 40. yeah never put your truck in 5th at 20 mph, its just like you dont start in 2nd, its hard on your clutch

 

[bowturkey]

The 5th gear @ 20mph was just a test. It does the bucking in other gears @ different rpms . And even when I'm not pushing it. After 166,000 miles it still has what it takes except for this problem. My ranger and I have been tru a lot together and I know when something isn't right . Just looking for possibilities of what to do to try to get it running like it use to. If it's burning rich before the computer takes over and I don't have a problem then what is it when it does take over. I also have a air/fuel mixture gauge on it for the past three years and that is working and basically showing the same results it has right along. It does show rich mixture when you first start and go and as it is warming up before the computer kicks in it will go to the lean side and while it is in the lean cycle if you want to call it that it still runs fine. As soon as the com. kicks in it shows up I keep thinking one of the sensors?