On the road rack dampener ? - PeachParts Mercedes-Benz Forum

JHZR2 · #1 08-28-2010, 05:57 PM

Hi,

Adjusted my tach, set idle to 750 and had adjusted RD pin. After sitting a few hours, car started fine, easily, but after pulling out of the driveway and making a hard turn with the AC on the car stalled. First restart failed, but after that car started and is running. Curious if this an indication that RD pin is in too far? Can this cause
Damage?

Also, set idle speed to 750 on tach and usually engine idles at 750, but once and awhile the engine will show low (600). Tach AMP and tach are fine, tach is not jumpy. Any ideas on that?

Thanks

JHZR2 · #2 08-28-2010, 10:29 PM

no issues on subsequent warm restates, but they do seem harder than before... Idle has also dropped... But overall fuel economy (just drove 120 miles) appears up. Should I take preptive steps before cold start tomorrow?

toomany MBZ · #3 08-29-2010, 10:51 AM

I understand if it's in too far you'll have hard starting issues. You may want to back it out a bit, but try a cold start first.

JHZR2 · #4 08-29-2010, 08:56 PM

OK, I am getting to my wit's end...

I have a gold rack dampener.

When I set the idle right and mess with it, I cannot for the life of me get the car to not lope at idle. Even with the RD all the way in.

I have tried to take the idle all the way down, disconnecting the linkage and unscrewing it. At some point just barely north of 500 RPM, the engine gets real smooth, no loping at all, even with the RD in an odd position.

However, with the idle low, two things happen - the engine bogs down pretty bad when something occurs such as shifting from neutral to drive or the AC kicking on, and when it recovers, it goes through a cycle up and down a number of times as the governor tries to get it back to normal.

At regular idle speed the odd things do not happen, however no matter where the RD pin is, including all the way in, the engine shakes pretty bad.

Engine mounts have less than 2k on them, and they are OE from the dealership. Valves adjusted at the same time. Injectors rebuilt and pop tested less than 1k ago. All of this was PM and part of other jobs like oil cooler lines - not really chasing the shake... It is just that now I have a hot idle shake that is my point of annoyance.

I can see the engine shocks flexing their mounts, but this is a pretty bad shake... That said, it is ONLY at complete, absolute idle, in neutral and AC off. As soon as some slight load occurs, like it is in D or the AC kicks on, it is smooth.

So what happens when your rack dampener is all the way in and you just can't get it right? Any reccomendations for how to get back to square one?

Thanks!

4thesporty · #5 08-29-2010, 09:23 PM

Don't know if it will help or not, but have you read/skimmed this thread:

http://www.peachparts.com/shopforum/showthread.php?t=234609

JHZR2 · #6 08-29-2010, 09:35 PM

I have read that thread in the past, and fuel may be part of it...

I should note that the idle is never rough, and the car drives very smooth. It is more of a shake than even a vibration, there is no notable vibration to speak of, I even had my wife sit in there and help tune wrt that. It is just a hot idle shake that really feels like the car is swaying with a periodic rhythm. My other w123s have done this at some point too... but Im really trying to get it figured out...

Junkman · #7 08-29-2010, 09:56 PM

What was the symptom that caused you to install the rack damper to begin with? Perhaps it was caused by something else and your current damper is installed too tight.

JHZR2 · #8 08-29-2010, 10:45 PM

the rack dampener was just what was in there... I didnt put a new one in or anything.

That said, the head on it appears to be gold, and it is an 82 car, so someone may have updated it in the past.

Im thinking it is an issue of my shocks/shock mounts... especially after this thread:
http://www.peachparts.com/shopforum/showthread.php?t=279663&highlight=idle+shake&page=2

Because the mounts surely get softer with heat, and the shocks prbably build up a little extra pressure with heat too, making the control stiffer... This is why I dont have an issue with this in as noticable a way when the engine is cold, and it mainly happens after being unloaded at idle when fully hot.