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LuvmyBenz2 07-05-2002 11:31 AM

Help - Moderator? - Idle
Pls help need to get this fixed asap, my other car is down as well and the only other vehicle I have is my Wife's and she has dressed it up to look like "Hello Kitty"

I have a 1987 420 SEL and this is what the problem is:

- Starts fine.
- Usually a rough idle. Not visible on the Tach but the Oil pressure gauge is going crazy.
- runs rough until 1200 rpm then it smooths out.
- Transmission kicks when shifting from 1st to 2nd but much better from 2nd to 3rd.
- Not burning any oil.
- No noticeable leaks.
- Vacume Lines look good

Also just started at same time..Clock quit working and Seatbelt light stays on. Fuses all look good. any connection??!!?

Have changed spark plugs & wires about 500 miles back when I had the almost identical problem but that fixed it.

What could be the problem this time? Appreciate any help as I DON'T want to drive the "Hello Kitty" car!

stevebfl 07-05-2002 11:51 AM

The first two symptoms bring to mind a common 420SEL ailment.

That is the open line to the vacuum modulator. To see this one must remove the aircleaner and look down the center of the rear of the motor. From an area close to the origine of the large vacuum booster source line, there will be a metal nipple (pretty hard to see). Look for the small line going to the trans modulator, it will just be hanging there.

The leak is small but it all goes in one intake runner and kills the cylinder at idle.

There could be lots of different problems and any that reduce vacuum will affect the trans shift but the line I mention is a fairly common occurance.

LuvmyBenz2 07-05-2002 12:11 PM

Damn Your good Steve!!
Took me awhile it looked like everything was O.K. The line coming out of the Nipple just fine..then I noticed that there was white line kind of laying there but couldn't see where it went to..then noticed that pointing downwards the opening for the line disconnected like you said...

NOW how do I get to it?? Any suggestions Long chopsticks ?? I'm going to put you on my Xmas list!! Thanks and as soon as I can get to it I hope that is the bugger!

Thanks Again


stevebfl 07-05-2002 12:59 PM

Ahhh, thats why I get the big money (VBG)!

Wait till its cold and you can get a hand on it. It may be easier to take the rubber piece off, place it on the line and then with one hand put the rubber back on the nipple.

LuvmyBenz2 07-05-2002 01:25 PM

Anybody wanna make some money!
O.K. I'll pay! I've tried for 1.5 hrs to connect a small tube to a nipple in the space only where 3 fingers will fit. In 95 degree heat and 60% humidity it won't go. This must be why Benz came up with this crap so people will pay. My hands are cut and I'm no where close to getting it in. The tube only has about 3 inches of play in it and remains in a 5 sqin area.

Steve will taking off the linkage help? or is there such a thing as
8" nosepliers?


stevebfl 07-05-2002 01:40 PM

I have never removed anything but the air cleaner. But then again, I usually do just like with you; I figure it out and let somebody else do it (BG).

There is no space for two hands, so you must either try and get the rubber section on the line and then work against the firm nipple or you can shorten the rubber section such that only a half inch extends past the nipple. Being shorter gives some firmness that can allow one hand to push the line into.

Good Luck.

old blue 07-05-2002 07:01 PM

Great one Steve!

Hey - does my trans modulator connect up the same way. (85 500 SEL)?.

I have similar symptoms, and am trying to eliminate vacuum leaks before spending $$ on fuel delivery parts.

Thanks, Michael

And for the record - they do make extremely long pliers/clamps with all kinds of tips. I have a couple for tying flies. A good fish tackle shop should have what you need.

stevebfl 07-05-2002 07:59 PM

The 500 is basically the same but the 420 and probably the 560 have a exhaust cross over pipe right next to these connections.

It should happen on 560's but I think I have only seen the problem on 420's. May just be due to there being more 420's.

LuvmyBenz2 07-05-2002 08:23 PM

My buddy has a 500SEL
Hey Old Blue, Just Like steve says..theres one there on the 500 as well, checked my Buddies car. Looks much easier to get to though. Still haven't hooked up mine but I'm going to go look for some 12" needlenose pliers.


william rogers 07-07-2002 01:21 AM

the transmission line on my 500SE goes very close to cross over pipe I have been thinking about putting a short steel line where it nearlt touches the the cross over pipe......
William Rogers......

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