GMC Repair: surging engine, speed repeat, steady speed

Question
sir i did exactly as you said  in the reply    but i  did not get the bump at the begining  or at the end it seems like it took a little of the surging out but it still does it a little any other ideas? sorry it took me so long to get back to you but i'm in the retail business and i've been working a lot of overtime.-------------------------
Followup To
Question -
sir; i have a 1989 s-15 jimmy  that i bought  new in 89 and i have always  done most of the mechanical work on it myself. the problem i'm  having is that when your going down the street at 25 - 35 mph. the engine jerks and acts like its missing a little when you try to hold it at a steady speed but after about 40 mph    it doesn't do it any more. i put new plugs, wires, cap and rotor on it and unplugged the brown wire under the carpet and checked the timing and checked the vacum lines and put a vacum gauge on the throttle body and the intake and got about 16 on the vacum gauge  from both places. any ideas?
Answer -
OK, Try this simple test:

1. When you are driving the vehicle as soon as you feel this problem do the following:


1. Maintain your speed.

2. Using your LEFT foot, LIGHTLY apply the brakes just enough to illuminate the stop lights and you should feel a BUMP. You MUST maintain your speed during this test.

3. release the brak pedal and withina second or three you will feel another BUMP.

4. While still maintaining your speed, repeat above steps 2 and 3 several times and each time you apply and release the brake pedal you should feel this BUMP.


5. OK, Now when you are back to feeling this problem, Again lightly apply the brake pedal as said above and this tiime do NOT release the brake pedal and see if your problem is resolved.

REMEMBER, You MUST maintain your speed at ALL times during this test.


let me know your results.


autohelp
meperganfortis@msn.com

Answer
OK, IF you did the test correctly, This would indicate a problem within the OVERDRIVE portion of your transmission.

You can try anothe tset:

Disconnect the rubber hose that goes to the EGR valve and pug up the rubber hose, NOT the VALVE and see if this makes any difference.


autohelp