230SL Jerk and Shuffle

[lagolag]

My 230SL with manual gearbox Jerks and Shuffle when I drive with light pressure on the accelerator in lower speeds, it disappears if I press the accelerator harder but then the acceleration is to fast for cruising. In neutral the engine rews well and the response be the accelerator is as it should be.
Can the Jerk and Shuffle be a result of worn engine and gear box mounts?
I can't be the only one with this problem, I have searched for answer in the forum and the technical section without finding a solution

[philmas]

Hi!
seems I have the same issue  with my 280sl (manual, euro specs) since the day I bought it some 20years ago...
Driving at low revs in slow traffic is a pita ,  maintaining a constant speed is a challenge when slightly depressing the throttle, mainly in 1st and 2nd gear around 1500/1800 r/min.
The car is "shaking" and hesitating unless I would depress the pedal frankly.
Starting and running is otherwise correct, plugs colour is nearly perfect; split linkage reveals no issue... the car has been serviced and tuned by specialists to no avail.

[philmas]

Does anybody have an idea? 
Could it be an IP related issue, or some throttle linkage problem...?
I have read someone in this forum (but where...?) stating it occured only with manual trans...?

[lreppond]

Have you checked your fuel injectors?  I had a similar issue at 25 mph… faster and there was no problem.  Once I had the injectors cleaned and calibrated I no longer had that problem.  If memory serves me it was injector four that was the issue. 

[philmas]

That's something to consider, thanks...
AFAIK, it's never been checked before.
 When the car has sit for some days, I notice it  always runs on 5 cylinders for a few minutes at cold start; everything returns to normal as the engine warms up. Could it be a clue?

[kampala]

I did not have jerking but was sensing some loss of power and upon checking the spark plugs, noticed that 4 cylinders were showing lean and two were perfectly tan.

I decided maybe I have a problem with my injectors -  and removed all six.  The 4 lean cylinders matched up with 4 injectors that clearly did not look as good nor clean as the the two cylinders with tan plugs.   Was glad (and surprised)  to see a visual correlation. 

I don’t have a pressure tester but I had a full set of new injectors so installed them. The difference in the drive was instant — significant power restored.  Could feel it immediately as I live on a hill and the car pulled up the hill effortlessly. 

Photos show the obvious difference between the injectors from a well performing cylinder and from a cylinder that was not performing well — these are the ones I removed, not the new ones. 

[philmas]

Wow, very instructive...!
Would you say changing the injectors is just  plug and play , or does it require special skills and tools?
What is "calibrating"?
Could a Diesel specialist do the job?

[Lorsar]

Mostly plug and play.  You'll need a injector/crows foot wrench to remove and a torque wrench to reinstall.  Do a search for "fuel injector wrench" and there's a thread with more detail.  Check the supplier list in the tech manual for companies that test and clean injectors.
https://www.sl113.org/wiki/Suppliers/Start

[kampala]

I would describe this job as relatively basic.  Any basic mechanic should be able to do it.

However, I don’t know if this will solve your issue — I had a fuel issue I could see from my spark plugs looking significantly different from plug to plug.  This was then corroborated by seeing the condition of the injectors. 

If you decide to remove injectors:

There is no calibration.  The injectors will release fuel at a predetermined pressure that you cannot change.

To remove the injectors you need two tools -  one that fits the injector and another that fits the fuel line connected to injector.   You need to hold the injector when you loosen the fuel line — in many cases they will move together, so you need to hold the injector while you loosen the line. 

I have the two “nesting” injection tools from hazet but the job can be done without them with “crows foot “ wrenches. 

Use penetrating fluid prior in between line and injector and on injectors if they have not been removed recently. 

Careful: don’t allow metal fuel line to get twisted and install new injectors carefully, like a spark plug so you do not cross thread.  The injector gets tightened a little more than the fuel line - I don’t recall the torque but you will find them with search.

[lagolag]

Thanks all for very good feedback on this issue, I will have look on the injectors and sparkplugs. I actually bought the special injector wrench tool before I got my Pagoda as I read a lot before buying my 230SL and there is much written about the injection systems sensitivity.

[lagolag]

I have been abroad for two weeks and the last thing i did before I left was to do the linkage tour as my idle was 1000rpm and I wanted it to be around 700-800rpm, I set it to ~750 rpm with hot engine, had to Turn down the air screw 2-3 full turns. I was a bit worried if it would start from cold and couldn’t test it before I left.
Now when I’m back home again I stated the car, it started directly and kept the idle on 750 rpm and driver away without hesitation, and the Jerk & Shuffle is almost gone!
I checked my old spark plugs and all 6 has a nice tan colour, so the injectors are probably in a good shape.
The only annoying thing is the noise from the rear axle top mount, got a new one by mail during my absence so that replacement will be done during following week.

Regards
Lars