SL/R107: 1980 450SL K-jet poor acceleration
Thread Starter
Senior Member
Joined: May 2004
Posts: 474
Likes: 36
From: Central Ohio
2017 C43, 1966 230SL, 2006 Jeep Rubicon
1980 450SL K-jet poor acceleration
Owned car about 10 years and have always been accepting of the poor off-the-line acceleration of this car, even though I know it's not right. Since swapping out the 1997 E300 diesel daily driver for a 2017 C43 AMG, this cars sluggishness is now annoying! 
LOL! I'll have to time it, but the 0-20 or 0-30 acceleration on my car is terrible. It picks up a little after that. Otherwise, running well. Transmission holds 1st gear for a while, then once in 2nd gear it goes quickly to 3rd gear. But, the sluggishness I'm out to correct is a lack of off-the-line performance. It will cruise at 80mph no problem.
I am going to start troubleshooting and I assume the distributor is a decent place to start. I need to buy a timing light. I'm concerned about vacuum since ACC and door vacuum doesn't work. I looked up vacuum diagrams and it seems that the engine/emissions diagrams never show anything about ACC or doors. Are these vacuum systems isolated from each other? It would be a good idea, of course! Just confirming.
LOL! I'll have to time it, but the 0-20 or 0-30 acceleration on my car is terrible. It picks up a little after that. Otherwise, running well. Transmission holds 1st gear for a while, then once in 2nd gear it goes quickly to 3rd gear. But, the sluggishness I'm out to correct is a lack of off-the-line performance. It will cruise at 80mph no problem.I am going to start troubleshooting and I assume the distributor is a decent place to start. I need to buy a timing light. I'm concerned about vacuum since ACC and door vacuum doesn't work. I looked up vacuum diagrams and it seems that the engine/emissions diagrams never show anything about ACC or doors. Are these vacuum systems isolated from each other? It would be a good idea, of course! Just confirming.
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Joined: Sep 2018
Posts: 3,243
Likes: 933
From: New Orleans Area
2015 E400 Sedan
Well the vacuum source comes from engine intake so any leak can cause excess air into engine bypassing Throttle body causing her to run lean.
Check all the vacuum lines especially if old and brittle and the end connectors.
Been too long for me to remember the 450 V8 engine... It was early 80's while in HS working at INDIE MB shop.
But I can say once running well they have some getty up and feel strong - CAr should be peppy and fun when you mash pedal - Not a dog but then not a newer AMG either.
Basic tune up will not hurt but may not help either.
good luck
Check all the vacuum lines especially if old and brittle and the end connectors.
Been too long for me to remember the 450 V8 engine... It was early 80's while in HS working at INDIE MB shop.
But I can say once running well they have some getty up and feel strong - CAr should be peppy and fun when you mash pedal - Not a dog but then not a newer AMG either.
Basic tune up will not hurt but may not help either.
good luck
Thread Starter
Senior Member
Joined: May 2004
Posts: 474
Likes: 36
From: Central Ohio
2017 C43, 1966 230SL, 2006 Jeep Rubicon
Thanks ygmn,
I've put on spark plugs, wires (could test the wires), dist rotor, dist cap in the last couple years. I'll start testing all vacuum lines with my MityVac. What amount of vacuum should I test with? How long should it hold? Should I test with car off or on? I don't know what to do/expect. I do have vacuum system diagram.
From another site, I confirmed that the engine/emissions vacuum system is completely separate from the vacuum system for doors, HVAC, etc. One less worry! Just twisting the dist rotor and seeing if it snaps back is one good test, then putting a vacuum on the dist to see if it moves is another. I'll also do a compression test, since it's not difficult. I'll buy a timing light and see where the dist is set.
I've put on spark plugs, wires (could test the wires), dist rotor, dist cap in the last couple years. I'll start testing all vacuum lines with my MityVac. What amount of vacuum should I test with? How long should it hold? Should I test with car off or on? I don't know what to do/expect. I do have vacuum system diagram.
From another site, I confirmed that the engine/emissions vacuum system is completely separate from the vacuum system for doors, HVAC, etc. One less worry! Just twisting the dist rotor and seeing if it snaps back is one good test, then putting a vacuum on the dist to see if it moves is another. I'll also do a compression test, since it's not difficult. I'll buy a timing light and see where the dist is set.
MBWorld Fanatic!
Joined: Sep 2018
Posts: 3,243
Likes: 933
From: New Orleans Area
2015 E400 Sedan
a god test for intake/vacuum leak is to spray brake cleaner or starting fluid around intake and vacuum lines...
and when the engine RPM changes when you spray - that area has a leak since it sucked in what you sprayed and cause engine to rev up normally.
and when the engine RPM changes when you spray - that area has a leak since it sucked in what you sprayed and cause engine to rev up normally.
