Mercedes-Benz Forum banner
1 - 20 of 26 Posts

·
Registered
1979 280sl automatic 110000 miles
Joined
·
31 Posts
Discussion Starter · #1 ·
1979 280SL is idling fast (2000 RPM) won't kick down. Would that be a faulty ignition control module?

Help, can't slow down............>>>>>>>>>
 

·
Premium Member
1975 450SL
Joined
·
2,440 Posts
There are waaay too many things that could cause a fast idle to immediately blame such an expensive part as the ECM.

Depending on your mechanical skills, you should get a manual & some tools and start shooting the trouble yourself, or go to a mechanic that knows these older type cars.

A lot depends on you and your particular situation.

If you want help, advice, suggestions, jokes, and good natured abuse, you've come to the right place. There are a lot of variables in the equation, so we will need some more info before anyone can start pointing you in the right direction, otherwise you get a "Karnak The Magnificent" type answer. Only not quite as useful.:D

Fill out your profile, give us the back story, and we'll try to help.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
Vacuum leak. Aux. Air/Air Slide Valve may be stuck and not closing.
 

·
Registered
82 380SL 96 SL500 03 SL500
Joined
·
6,182 Posts
Vacuum leak. Aux. Air/Air Slide Valve may be stuck and not closing.
Those would be my guesses as well.

I don't think the ignition control module has any input on idle speed on this model.
 

·
Outstanding Contributor , Bob's Your Uncle!
83 280 SL- 5 speed-The PIG
Joined
·
32,203 Posts
1979 280SL is idling fast (2000 RPM) won't kick down. Would that be a faulty ignition control module?

Help, can't slow down............>>>>>>>>>
Please fill out your profile.

Is your car stick or auto?


I had a bad thermostat that wouldn't allow the engine to get up to operating temperatures.

Thus the WUR kept feeding it fuel which in turn kept the idle high.


It could be any number of things.
And your details are a little on the thin side.

Is this car new to you?
Did this problem happen over night or was it gradual?

Did the high idle start after some other maintenance function was carried out?
 

·
Registered
1979 280sl automatic 110000 miles
Joined
·
31 Posts
Discussion Starter · #6 · (Edited)
fast idle

thanks for all the input. I am appreciating the help. This is the straight dope

Recently purchased the 280SL. Needs work and I knew that. First problem is finding a good repair manual. Tried books4cars.com but they sent me the wrong book.

1979 280SL, Model W107, Chassis 107.042, Engine 110.982/6 auto trans, We were told it was a 1979. You strike me as a bunch of guys who like numbers, so here's the VIN 10704212004812 I was told to put WDB in front of this to find parts. Took it to a dealer without great results - they were too busy and didn't have time to talk. Did give me a list of things to fix:
Said they tried to adjust mixtures for the idle problem - didn't work
I read on another site something about the ICM.

Aware of possible thermostat problem, but it seems to be heating correctly, but won't know for sure until I pop it out.

I now turn my questions over to my superiors :bowdown:
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
Not too difficult to check which engine you have. The model and number are stamped where shown.
 

Attachments

·
Registered
1979 280sl automatic 110000 miles
Joined
·
31 Posts
Discussion Starter · #9 · (Edited)
fast idle

# s would be 110 986 12004 404 w ? on last 0 could be a 8 snow yes but not yet opps it is an 8 lets try again 110 986 12004 484
 

·
Premium Member
1975 450SL
Joined
·
2,440 Posts
The best easy manual to get is the Benz service manual on CD-ROM.
I got mine from Mercedes Benz Manual - Mercedes Repair Manuals - Mercedes-Benz Service Manuels . It has been an invaluable asset. The Hanes manuals are suspect, as they are edited for size.

If you have the time, tools, and inclination, you will be rewarded with the immense satisfaction of being able to detect, diagnose, and repair a problem in such a manner as to save yourself a sizable chunk of money that would be otherwise spent at the dealership or possibly a questionable mechanic.

Good luck, and welcome to the madhouse.:D
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
The CD will help on the chassis but does not cover the 280SL or the M110 engine.
 

·
Registered
1979 280sl automatic 110000 miles
Joined
·
31 Posts
Discussion Starter · #13 ·
fast idle

im finding manuals for all models except a 107 280sl:crybaby2:
 

·
Registered
1979 280sl automatic 110000 miles
Joined
·
31 Posts
Discussion Starter · #14 ·
you guys are fast 1 for chassis 1 for engine ? this is harder than understanding my wife:surrender:
 

·
Registered
'80 450SLC Afro RHD Ikonengold
Joined
·
3,195 Posts
Before you can think of repairing it, try to find all the info on the net that relats to "CIS" or "K-Jetronic". Read all the explanations inclusive of those that are for other makes. There's plenty available specially for VW Golf (Rabbit) I.

Unless you generally understand how does this injection system operates in most of the conditions, advises you get here will be somewhat confusing in many cases.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,777 Posts
You actually try to understand women?
I gave that up in kindergarten.
 

·
Registered
'80 450SLC Afro RHD Ikonengold
Joined
·
3,195 Posts
understand may not what seem seam two words in between ;)

------------------------------------------------------

I recon if a vacuum leak is to be blamed for 2000rpm, it would have to be audible, especially if throttling.
WHat about idle adjust screw, does it bring the rpm down AND does rpm go down* as engine warms up?

* down as in terms of slowing down a bit at least.
 
1 - 20 of 26 Posts
Top