Help with diagnosing daily driver...

[andrewb70]

I am completely stumped as to what is wrong with my daily driver and I am hoping some of you might have some ideas. I have done extensive searching around on related forums and the answer seems to be as simple as IAC to recessed exhaust valves...

Vehicle: 1999 Mazda B2500 (Ford Ranger) 5 speed.
Almost 100K miles well maintained.
New plugs and wires at 75K miles.

Symptoms: Extremely rough idle when cold. This doesn't happen upon initial start up, but it starts happening after first drive and I come to a stop. From that point the engine starts to shake violently enough to make the whole truck shake. The shifter handle shakes hard and the whole truck shakes. It smooths out if I give it a little throttle, but when it comes down to idle the shaking resumes. Once it comes up to temp the idle smooths out and is mostly normal. However, when I blip the throttle and the RPM come back down, on occasion the engine will idle rough again, but will smooth out in 3-4 seconds. I can replicate this fairly consistently.



There are no codes or pending codes.

I have replaced:

IAC
Temp sensor
EGR valve
Hose from valve cover to TB
Cleaned the TB (took it off and new gasket)

Any help and ideas are appreciated.

Andrew