im thinking power steering pump........ ideas? 87 3sfe auto cruising about 40mph, hit brakes a little bit but then coast (without being on the brakes) and the idle will fall tell about 900-1k rpm and then buck up and down till im about 15mph, starts around 35ish or so. it will buck going down hill without hitting the brakes as well. it also does happen if im on the brakes as well. the only time it doesnt is if i slam on the brakes. i have all new master and cailpers with rotors and pads as well. i plugged the booster and that felt better so i bought a brand new one....issue remains. car runs fine except this....no vacuum leaks detected , car will idle just fine at park or cruising speeds.....enough power...... it does shift funny tho, i did a tranny flush not long ago but the problem happened way before that happened. the idle does stick (not too bad) i just replaced the tps and had that installed by a shop, cleaned out tb and acv replace gasket on tb as well. this is more of an annoyance then a major problem as the car runs great otherwise. if you need a video ill get one made ideas?
Check your TPS according to the manual, check the valve to the brake booster is sealing in one direction
stick some clean hose on the end of it and blow in it. Air should go through from one direction and should not from the other.
One car I checked had a slight leak on the m/c, at idle (high vaccum) it would suck fluid into the intake manifold and idle stupid with white smoke at the exhaust. Check for brake fluid in the servo and the vaccum pipe also
