I've got an '85 Ford Ranger with a 2.8L V6 that runs fair in town, (more often than not) but on occasion runs very poorly, as if the timing is completely off.

For example, I ran it to the store today, and it coughed and bucked with little power on the way there, but after restarting it later, it ran as good as it usually does (not great, but OK at least.) Other times it will run fine, then run very rough, then return to normal.

This vehicle has given me many fits in recent years, including multiple carb rebuilds, new distributor, tranny rebuild, etc. I only trust it in town, but on occasion it just seems to go south. Any ideas? After all of the $$$ and effort I've taken to get get it where it's at, I'd like to conquer this one last issue.

 

There are a number of sensors that can fail (including the oxygen sensor), as well as solenoid valves for vacuum controls. I've had a number of them fail in my '85 2.8 also. The way I temporarily got around it was to disconnect the electrical connection on the carb. At least that way it doesn't get a bunch of erroneous incorrect signals from the computer, due to failing sensors & such. Naturally, emmissions will suffer, but they are probably ALREADY suffering if the truck isn't running right. At least it always runs consistently & predictably. If indeed it is the timing rather than the carb, as you suspect, I'm not quite sure how to conquer that right off hand. I do know that SOMETHING senses manifold vacuum as one way of letting the computer know where to "set" the timing during acceleration at various throttle openings. If timing is your problem, the device that detects the manifold vacuum could be malfunctioning. I think there is also a ping sensor. If that malfunctions, it could have the same effect (delaying, rather than advancing timing). The other thing I did that helped some was to advance the overall timing (by rotating the distributor), until I got some pinging on low humidity days, then tweak it back JUST ENOUGH to minimize or stop the pinging. This way, the timing is always at the "hairy edge" of over-advanced. It has a bit more pep that way. You might also try cleaning the carb out real good (spray carb cleaner, and gas treatment, as well as some methanol AND isopropyl antifreeze). GOOD LUCK!