Hello all,

I'm just wondering what is needed to lossen the nut to make a simple idle adjustment. A regular 14mm socket wont fit over the screw and it's to confined to fit anything else down there. I didn't see any special tools referenced in the service manual either. It's not to the point of stalling but it just really starts to shake somtimes from running so slow. Thanks guys.

I would check several things before adjusting the idle which may just mask what the real problem is.

Valve Adjustment- When was the last time?
Rack Dampner Bolt- Have you tried adjusting it? Does it need replacing?
Injectors- Have you loosened any fuel lines, one-at-a-time to see if it changes?
Motor Mounts- What shape are they in? Bad motor mounts can cause an oil cooler line failure, which can ruin an engine in short order.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )

If you do end up adjusting the idle screw, use a 1/2-inch drive deep socket. It should be long enough and you can fit a screwdriver through the top hole of the socket and turn the adjuster while holding the nut in place.

First thanks for all the suggestions. I just got the car in January so I havn't gotten around to adjusting the valves. I do notice they are a bit noisy when the engine is cold. After warm up pretty much no valve noise is heard. Maybe there is one tapper. The valves are definitly on the list. I consulted the shop manual and it seems there are a couple wrenches need for the adjustment. I know I'm capable of the procedure but is it worth buying all the tools to do it or is it just easier to let a shop do it? Once the valves are in adjustment is it normal to hear valve noise even at cold start?
As for the dampener bolt. It appeared to be an 1/8 inch or so out from the lock nut when I got to it. I adjusted it in and out with the engine running and I didn't notice any difference in the way it ran. I ended up just screwing it in all the way just to see what long term affect it may have if any. I noticed no difference in anything. It's almost as if the engine has a normal idle setting and a lower idle setting that it just randomly toggles between somtimes. Mostly choosing the lower idle setting. The lower idle setting causes a lot of vibration in my new air induction mount and related components. How do I know the dampener is good or needs replacement?
As for injectors, no I didn't loosen any to notice miss. The engine does seem smooth otherwise but I will make this check soon.
For the engine mounts I just did the tried and true hold the brake in drive and reverse test and the engine didn't seem to list in either direction greatly. However my only reference is the way most engines move in general.
I'm replacing some leaky injector bleed lines this weekend so I'll crack the injectors loose and see what I notice there and report back. Thanks again

Be extra careful if you decide to adjust that idle speed bolt. After 20 years, the nut is not going to want to move. Apply too much torque and you break off the mounting lug for the bolt. If that happens, you'll be in a world of hurt.

Make sure you spray the bolt down with PB Blaster or Kroil for several days prior to the attempt, and, don't force it if it won't go.