Hi Guys

Well my 88 Ranger project continues. Now when I'm sitting idle the engine rpms pulsate up and down. This is on a 2.3 ltre, 2wd. I have put all new plugs, wires, coil, and ran injection cleaner, but it still hunts when sitting idle.

Any ideas?

 

45 reads & no suggestions, so I'll try & get the ball rolling.

Have you scanned the computer for trouble codes, if so, post All code numbers, as they can offer up good trouble shooting clues.

Did this problem began suddenly after some event????

Is it doing this with the A/C on????

If the A/C is cycling on & off faster than normal, because the charge is low, it can cause the idle to seem to be acting out, so turn the in cabin heater/ac switch to off & see what happens.

What happens when you unplug the IAC, does it still act out when you use the accelerator to hold the idle speed where it belongs???? If so, maybe look to a vacuum leak, like a sticking PCV valve, or maybe the fuel pressure regulator is acting out, so try removing & plugging it's vacuum line & see what happens. If it straightens up, maybe suspect the regulator, especially if it's vacuum line is wet inside with fuel.

If it's an automatic tranny, pull the tranny vacuum modulator intake manafold vacuum hose & see if it's wet with tranny fluid inside. If so suspect the vacuum modulators diaphragm is leaking & sucking tranny fluid into the intake manafold & messing with the air/fuel ratio.

Same for any under hood or in cabin heater/ac control vacuum line, so perform a good under hood & dash vacuum line condition check up.

A bunch of thoughts for consideration, let us know what you find.

 

Thanks for all the advise PawPaw. I will take the steps you mentioned but i have no A/C, and the tranny is 5 speed manual. I'll get back to ya with codes and results of vacuum leak hunting.