Well, I bit the bullet and replaced the UIM with the APN model with the sleeved EGR opening and reduced diameter EGR stovepipe. I also changed the gaskets on the LIM. Then flushed the cooling system. That all went well but....

Now I have a fast idle (1500 in neutral, 1100 in drive). Also have codes 107 and 108, and 121 (low manifold and high manifold pressure). I have checked for vacuum leaks by spraying Gumout around the UIM and throttle body but no change in idle.

Any thoughts?

Also, my serpentine belt now slips when warm. It was new about 1 year ago. Any tricks short of replacing it? I heard to avoid belt dressings, but dishwashing soap helps?? I am not ready to try that unless I have a new one in my hand.

I'd start with insuring the sensors are plugged in and cleaning the grounds.

At idle, remove the oil fill cap. Sucking? If so, you missed an o-ring on your PCV valve.

If it'* not the PCV, check the idle air control.

On the slipping belt. De-tension the belt and slip it off the alternator. Spin all the pulleys by hand. If the pulleys all look good, and spin normally (no drag), you may need a new tensioner.

You can check belt tension with a relatively inexpensive gauge called a "Clikit." You need to get the right one for the range you want to read. They cost about $15.

My '95 FSM says the belt tension on your belt should be between 50 and 70 pounds taken as the average of three readings. Measure tension midway between the generator and the ps pump. The three readings are taken after the engine is stopped and:

1. With engine warmed up and no accessories on
2. After tightening (clockwise) and releasing the tensioner
3. After loosening (counter-clockwise) and slowly re-applying tension.

Willwren hit the nail on the head. We could hardly remove the oil filler cap with the engine running due to the vacuum.

So yes, we were missing not just the o-ring, but the PCV altogether!

As far as my slipping belt; I checked the alternator, water pump, power steering pump, and idler pully and everything spins easily. The tensioner takes a breaker bar to get it to release the tension enough to get the belt off. So I am about at the point of replacing the belt. I am thinking that coolant got on it when I flushed the system.

Any tricks on getting the front engine mount off so I can get the belt off?

You only need to remove one bolt from the mount and slide the sleeve out to replace the belt. Do a search - explained many times - with pix, too.

Here'* one:

http://www.bonnevilleclub.com/forum/...ic.php?t=25394

Here'* a pic:

Bill B: Great picture. I checked the other threads as you advised and it appears fairly straighforward. Looks like I need to buy an E10 torx socket and just do it.

I have the factory service manual and now that I have read these threads it agrees with only needing to remove the bottom mount spacer. BUT, obviously the tech writer was not a mechanic, or the writer was a mechanic and not a tech writer - very obtuse.

I tried this a couple of years ago and gave up. Landed up paying a mechanic $100 labor to install my belt.

Wish I had found this forum a few years back. You guys have all of the answers.

A missing PCV valve can create a high pitched whistle noise from the engine. Are you sure it'* the belt making the noise or is it the missing PCV?

We still had the noise after replacing the PCV. But I put a 3rd coat of STP belt dressing and the noise ended. So I am happy to avoid changing the serpentine belt at this time.