99 ranger 2.5 2wd auto has this irritating shake shudder vibration when it's stopped at idle. Drives down the road great then come to a stop and after a second it'll shake. Also the AC compressor clicks on and off quite frequently, like every 30 seconds. I'm not sure if it's related at all but it's also annoying. It seems to get a surge of power when the compressor clicks.

It's only got 68k on the clock and I just did all the plugs, fuel filter, pcv, thermostat, and brake sensors because the abs and cruise aren't working

 

Welcome to the forum

All 4cyl engines have vibration issues, because they only fire every 180 degrees of crank rotation.

So they are usually setup with higher idles, 800rpm or so, 850 with automatics.

And any misfire at idle will really shake 4cyl engine

Check motor mounts first
Open the hood so you can see engine in the gap under the hood
Start engine
Set emergency brake

Put in Drive and keep foot on the brake
Give it a little gas
Watch for engine to lift up

Repeat test in Reverse
look for engine to lift up

A loose or broken motor mount will allow engine to lift up in one direction.

Engine should move side to side a bit but not lift up


In Defrost mode the AC compressor will cycle on and off, or of course if AC is on compressor will be on and not cycle.

If it seems to be cycling too fast then it is probably low on coolant, so low pressure switch is turning off compressor until pressure comes back up and then compressor starts again.

Computer monitors if AC compressor is on or off, when on the computer will bump up the idle because compressor is a load on the engine.

So if compressor is cycling on and off then idle would be up and down with it

 

yes??? but did you replace the ignition wires

going old school here , engine shaking also has to do with the spark plugs not receiving enough voltage

improper ignition , not a misfire , the fuel / air mixture does not completely burn

 

No I didn't do the wires. They were all in like new condition just like the plugs.

 

clarify ?? in like new condition

you need a digital multimeter to test for ohms resistance

high ohms resistance means wires need replacing any ohms reading above 16 to 17 ohms

the wires need replacing

 

I've come to the conclusion that it's something to do with my ac pump. Now that it's warm out and I'm not using my defrost it seems to have stopped.