Rack Bolt Adjustment, what is the best way to do this?
 

Hi,
I have a problem with a rough idle and sometimes it is smooth, sometimes it is rough.

I have the valves set, air and fuel filters are new, no air in the fuel anymore, good injectors out of my parts car that idled smooth as silk!

I put a new rack bolt ( gold ) in about a year ago and that seemed to "set just fine" worked great back then.

The problem acts a bit different than when I put the rack bolt in a year ago, but similar, the engine wobbles really bad when cold, and when the idle is set at 800 rpm's, 950 it is smoother when cold but not great.

The main thing is What is the best way to set the rack bolt?

Should the motor be at 80C and the idle at 800 rpms or ?
Thank You all for your help!
Jim

Here are some of the instructions that came with mine.

I'll suggest the rpm to be ~750.

Thank You for the info toomany MBZ, I have to re adjust my idle down to your 750 RPM recommendation.

Right now it is at about 850 and I ran the rack bolt all the way back out until I thought it was going to fall out, then ran it back in, all the way in and I didn't notice any difference, I know that sounds crazy.

Because when I first put this gold rack bolt in, it made a lot of difference the way the motor idled, but know it really doesn't matter where I put it, it still wobbles, It is driving me crazy!!!

I will work with it tomorrow, thanks again for the info!!!

Hi
When my rack damper bolt was out of adjustment my engine would idle smoothly until it warmed up and then start shaking. Cold shaking could be a glow plug problem.
Joseph

I checked the glow plugs before I started this venture, but I will check them again.
I didn't physically take them out and hook them up to 12volts of power, but I tested them by pulling off the "relay cover" hooking my testers alligator clip up to one of the screws that holds down the fuse on the relay and with the pointer end of my tester with the light in it, I stick it into the glow plug wire harness socket, that has the numbers 1 threw 5 that is normally plugged into the glow plug relay.

Over time I have learned that a dim light can be carbon/weak glow plug or no light of coarse a bad glow plug.

This has served me well in the past, but is not the perfect way!

Thank You for your input!
Jim

Hi to you all,
Ok, before I started the car ( 84 300SD ), I backed off the rack bolt, then screwed it in till I felt a little pressure, then locked it down and went for a drive until the car was warmed up.

I stopped adjusted my idle down to 750 RPM's ( car was in gear, lights and AC were all on ) and then made the adjustment to the rack bolt, I screwed it in until I heard the motor change in RPM's, that seem to be the smoothest point, locked that down and went for another drive ( hard and fast ) stopped and very slowly adjusted the rack bolt in and out until I found the sweet spot and am going to leave it there for now.

I still have a wobble but not bad, I changed the motor mounts last week and they are nice and soft, I believe the motor shocks are shot and the rubber on top is also shot.

rack damper should be donw with idle screw backed off. I couldnt get that to make any difference.

Im kind of in the same shape as you. IMO you need to start looking elsewhere. Check my threads which include pictures, videos and my process. Search for threads Ive started and youll find them easily. Lots of good info inside.

I have a fuel rack sensor on my IP that wires into a control box? Where could they hide that little black box? I am wondering if that has gone crazy!

My car is a 1984 300SD, California car, if you look at the vacuum chart, it looks like a night mare!!!

I can't get the chart to up load:eek:

I want my 1982 240D back!

That wire goes to your EGR computer located behind the passenger kick panel. If your EGR is disabled (it should be:)) don't worry with it.

There is some talk of a "magic panel" you can remove and adjust your idle from the EGR computer, but I think that has been debunked.

Thanks for your response Adam,

So if I understand you correctly, this control box will still operate the fuel rack sensor properly if the EGR valve is disconnected?

With that said, there is still a temperature, vacuum converter, RPM and coolant sensor that still go into the control box, will any of these NOT working properly effect the rack sensor?

What does the rack sensor do :confused:

Rack dampener just compensates for an out of tune IP.

How do I tune it?

The way it was explained to me, was the rack position sensor is just an input to the computer. The computer does not control the rack position.

I have removed all the EGR components with the exception of the computer and plugged/rerouted all vacuum lines.

The IP can only be calibrated on a test bench by a pro, the best you can do is time it correctly using the drip method, or RIV lights. If you KNOW that the IP has not ever been re-timed then you can help bring it back to spec by correcting for timing chain elongation by installing a new timing chain or by installing an offset woodruff key.

Thank You Adam, for the clarity and input!

My pump was adjusted, April 28th 2008 by the timing light, it was moved about 3/16" of an inch from its original stamped mark which I believe is a hug move.
Timing chain was replaced just before the timing of the pump, I may go ahead and change the timing chain and have the pump timed by the drip method, I am at 90,000 miles on the chain.
The motor is at 305,000.....may be time for another pump.

I drive a lot.

It would be prudent to check your chain elongation before simply replacing the chain though.