98' 2.5L idle hesitation? HELP!
 

Hi everyone! Whelp, after a year of ownership and no problems, I've finally hit a snag. First and foremost, a little about my car -- its a 98' with 100K (just hit it this weekend). Got it last year with 84K miles. I'm the 3rd owner and have most, if not all the maintenance records going back to when it was new. I do oil changes every 4k-5k miles.

Recently, I noticed a slight hesitation/sound when idling and a tapping noise coming from the rear. RPM's remain steady at 900ish with no fluctuation. I get a little rattle and white smoke upon startup that goes away once its warmed up. However, I now blow a little more smoke when I rev it up and then let it go back to idle (not belching out smoke, just a steady mist of white). If I try to take the oil cap off, I get suction, but can still remove the cap. When I do, the car bogs down like its going to stall. A little smoke comes out, but RPMs remain at 900ish.

Is my AOS on its way out? I'm not sure if its the original or not.

Also, just noticed yesterday my coolant was abut an inch below the min line. After getting home last night, I saw a very small amount of what I think is coolant dripping form the right rear (exactly where the over flow tube hangs down above the control arm). No leaks in the trunk or under the carpet, but some condensation on the lid just above the oil/coolant caps.

Any and all help greatly appreciated. Here's what I knows has been replaced:

Belt: 94k
Spark Plugs Changed: 96k
Water Pump: 68k
Coolant Reservoir: 70k
Coolant Expansion Tank 83k

OK, what you likely have are several issues that aren't related. My thoughts on them.

The tapping at startup is likely sticky lifters. It's happens and there's nothing short of replacing your lifters and doing open engine surgery that will fix it. Continue regular oil changes and turn up the radio. You can read more about it if you search for sticky lifters.

White smoke is usually related to aos and seeing as you're not sure if it has been replaced it is likely due.

The other item that controls idle would be your mass airflow sensor. This is another part that has a life expectancy and I also see it hasn't been replaced.

Do you do maintenance yourself?

Yep, I do all my own maintenance. Just ordered a new air oil separator from pelican, so should be getting that next week. Figured its a good place to start. As for the MAF, I'll give it a cleaning and see if that helps. I'm not getting any CEL, but wanna do as much preventative as I can in the meantime.

Your car has an idle air controller on the drivers side of the throttle body. The valve gets dirty and may be worth your time to remove an clean with some throttle body cleaner.

Your AOS is failing.

For coolant issue, since you don't think your tank is bad, pull the access panel behind your seats and start your car to see if you see any evidence of a WP leak. It may just be weeping a bit or perhaps you'll find a WP bolt that needs to be tightened a bit (torque to 7 ft-lbs).