Author Topic: 230SL low-speed "bucking" on deceleration  (Read 2565 times)

lowpad

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230SL low-speed "bucking" on deceleration
« on: May 30, 2020, 18:30:06 »
My 230SL (and even my much newer 993) has always had a little bit of part throttle "bucking" on slow-speed deceleration.  A typical situation would be coming up to a stop sign at low speeds, in 1st or 2nd gear, wherein the car starts to buck, requiring either a full lift off of the accelerator or putting the car in neutral and just coasting.  This situation just got worse following a bunch of fuel system work to address a high idle and improve warm starting.  I've looked through past posts on this and related topics, but can't find any other similar situations.  I know that later cars had a fuel shutoff solenoid added to the FI pump, but the 230SL does not have this.  I can live with a bit of this, but the situation is now much worse than before.  Many thanks in advance for any suggestions.  Lowell
« Last Edit: May 30, 2020, 19:54:26 by lowpad »
1966 230SL (6/66 build)
French export
4-speed manual
158 Exterior / 040 Hardtop
2001 SLK230
1996 Porsche 993
1991 Acura NSX

mistertj

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Re: 230SL low-speed "bucking" on deceleration
« Reply #1 on: June 06, 2020, 22:26:13 »
I occasionally got that but I was the cause...not able to keep my foot perfectly still. The gas pedal is very touchy, so I just lift my foot off of it when coming to a stop...and rest it on the brake.

lowpad

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Re: 230SL low-speed "bucking" on deceleration
« Reply #2 on: June 07, 2020, 17:41:52 »
Thanks.  That's my currently what I do, but I somehow doubted that the esteemed Mercedes development team would have accepted that as a solution!  I've noticed that my car doesn't have a throttle dashpot.  Going to see if that might help somewhat.
1966 230SL (6/66 build)
French export
4-speed manual
158 Exterior / 040 Hardtop
2001 SLK230
1996 Porsche 993
1991 Acura NSX

Melburnian

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Re: 230SL low-speed "bucking" on deceleration
« Reply #3 on: June 10, 2020, 07:42:40 »
An amateur here but have you checked the functioning of the dashpot? Mine was wrongly fitted with one to suit a 280slwhich is a different size  and wasnt engaging. Now I have replaced it the gear changes are much smoother requiring less skill  on the pedals.

lowpad

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Re: 230SL low-speed "bucking" on deceleration
« Reply #4 on: June 10, 2020, 23:56:55 »
Thanks.  I actually don’t have a dashpot and plan to install one. 
1966 230SL (6/66 build)
French export
4-speed manual
158 Exterior / 040 Hardtop
2001 SLK230
1996 Porsche 993
1991 Acura NSX

Melburnian

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Re: 230SL low-speed "bucking" on deceleration
« Reply #5 on: June 12, 2020, 01:11:55 »
yes sorry I just read your post again. Installing one will definitely improve the ease of driving. It prevents the revs dropping off quickly so gear changes are smoother. Whether it totally solves the issue? you never know your luck!

rumb

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Re: 230SL low-speed "bucking" on deceleration
« Reply #6 on: June 24, 2020, 17:23:43 »
Is your differential worn out? That will cause bucking when soft decelerating.

Benz Dr.

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Re: 230SL low-speed "bucking" on deceleration
« Reply #7 on: June 24, 2020, 22:42:59 »
Check to see if your idle mixture is rich or lean at hot idle. Your engine could be hunting for fuel as it comes off of higher engine speeds.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC