Suspect 99 malibu broken timing belt

Have you cleaned the throttle body and throttle body valve? have you cleaned the idle speed control air bypass valve? are the injectors clean? Are there any fault codes in memory, do the things I mentioned if you haven't already. Also hard engine mounts can cause roughness at idle. Another thing is the timing belt tight?

Check fuel pressure. Air filter could be really clogged, usually they will collapse first. Then check for exhaust pressure out of the tail pipe. Little pressure or it's really hot. The catalytic converter/s are plugged up.

If there are no cables coming off throttle body to control throttle there is no Idle Air Control valve. the idle is controlled electronically by the computer. If car is idling rough you can clean throttle body to correct this problem. If you do have cables to control throttle the IAC valve is located right next to throttle body attached to it. Hope this helps

A it's starting to run rough and stall what happens if you spray a little carb spray into the throttle body? Will the idle smooth out?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

take the head off bent valves thats for sure

hi has this a turbo if so would say air leak,check hoses

it sounds like you have a injector leaking down into one of your cylinders so it is flooding out a cylinder thus runs rough and long cranks.

ok.....as far as the oil on them it is possible it is only the spark plug tube seals located on the inside of the valve cover,in fact if you can remember when you took the old plug wires off the boots of a couple propably had oil on them.now as far as the real problem I would recommend checking the timing belt it is possible it jumped time,its pretty simple just remove the valve cover(gonna replace the seals anyways)and top timing cover.roll the engine around and look for the cam and crank marks.if you need anymore suggestions or help let me know have a good day DB

are you getting fuel to the engine? are you getting spark? check fule pump cut off switch on drivers side kick panel. good luck.

check your transmission fluid,the motor will stall when fluid is low