Hey guys,
I own a beautiful 1992 ford ranger 2.9L v6. The truck recently started having a rough idle, very up and down. It doesn't matter if i have been running it all day or just starting it up for the first time of the day, she idles rough. Driving is fine she runs well as long as im moving, but as soon as i hit a red light or stop sign, she starts to idle rough. Can anyone give me some advice?

 

Check for air leaks, loose or plugged PCV, broken vacuum lines, vacuum lines that have fallen off the 'tree'[manifold on the firewall], or a leak in the tubing leading from the MAF to the throttle body. If you had a MAP sensor, I would suggest that was a good candidate for the problem. If your MAF were coated with gunk, it could throw a code, and give bad off-idle response. Don't know if a MAF would cause bad idle, but it makes sense that it could if it were real intermittent in its data.
If your gas mileage is still the same, and you get fast idle for a while when cold and decent cold driveability, that would tend to rule out bad air and coolant temp sensors.
You could also have a gummed up IAC[Idle Air Control], that is not responding to the commands from the ECM. A check on that is to see if the idle changes when the A/C is engaged. It should bump up a bit.
tom