4.0 ohv engine running rough at idle

[jme94xlt]

My 4.0L OHV engine in my '94 has been running really rough lately at idle and when the throttle is not engaged at high speeds (60-70mph). It feels as if the entire car is going to vibrate out from underneath me. I've had it looked at several times, and replaced the fuel pressure regulator and the sensor that controlls the EGR valve (forgot what its name was). I had a new set of platinum plugs put in (they haven't been changed in 3 years) as well. Does anyone know what I'm talking about here? I'd like to know what's going on. I bought a $30 code scanner from AutoZone, and ran the tests on it, and it gave me codes 536, 538, and 539. I looked these codes up on therangerstation's website:

536 (O,R,M) Brake On Off open or shorted to ground - BOO
538 (R) System did not receive "goose" test - TESTS
539 (O) System shows voltage at PCM pin 10. Is A/C on ?

If 536 came on because the parking brake was engaged, then that's why. If code 539 was because the A/C was either on or off (I forgot which), then that's why. Code 538 I have no clue about, nor do I have a clue what a "goose" test is. I hope someone can shed some light on my situation. As I said, I've had it looked at several times, and everything I've tried so far hasn't fixed it. I hope someone else on this forum has either been in the same situation or knows what I'm talking about, because I need to know exactly what's wrong with my engine so I can have it fixed. I plan on driving this truck for the next 3 or 4 years, unless it keeps giving me problems like this one. Thanks for your help.

 

[mrboyle]

I cant help much on the running problem, but I can explain the codes.
The codes you recived have nothing to do with the running problem. When running the Key On Engine Running (KOER) diagnostic test the computer checks for each of the three items you recived codes for. Testing with one of the $30 scanners you do not recive the information on when to perform the tests, so it just gives you the codes. Code 536 is because you didn't press and release the brake pedal (because you weren't told to). Code 538 is because you didn't snap the throttle (goose it) when the computer wanted you to (again, because you weren't told to). Code 539 is because the A/C was on during the test.