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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #1
No engine codes or faults showing.

At low revs, 1500 or less under light load like a gentle uphill my 320 has a very, very light 'hunt' or surge. It's almost imperceptible, not enough to really move the rev-counter but I can feel a very slight pulsing of the power sort of ebbing and flowing at about 1 to 2hz!

Any ideas? Could it be fuel pressure? The pump in the boot/trunk seems to be very noisy at times.

Apart from that the engine appears to be performing well.
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #3
Flieger I think perhaps your reply is mixed from another thread?
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #5
I'll try replace the filter and see how that goes. thanks
 

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Premium Member 2006 SLK350
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6,796 Posts
..no...it was meant for you.. You raised the possibility of fuel pressure. With full throttle the pressure drops to its lowest level...

Maybe run some techron through it... may be dirty injectors.
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #7
..no...it was meant for you.. You raised the possibility of fuel pressure. With full throttle the pressure drops to its lowest level...

Maybe run some techron through it... may be dirty injectors.
Ok i'll try that too.

No problems at anything but he lightest throttle setting and it's so, so small but I can feel it. :)
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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98,233 Posts

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #9
Air filters replaced no difference.

Fuel filter ordered.

No techron available 'off the shelf' in the uk so have tried a dose of 'redex advanced' as a trial. It has definately made a big difference. Pickup and acceleration better than it was before and even smoother than ever!

Haven't detected the hunting again yet!
 

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The first symptoms of the fuel filter I had was an increasingly sluggish performance in accelaration as the tank became empty, then after a few months it started to hesitate and surge on heavier acceleration

I used redex for a while with noticable difference but nothing like replacing the fuel filter did, it was like a new car.
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #11
The surging problem had neither got better nor worse over the past month or so since I started this thread. I have recently been doing some contract work about 250 miles from home and doing the run once or twice a week. Lets just say that the car has had the chance to shed any carbon buildup over the few trips. :) The car is rock solid at some impressive speeds.

But the hunting was still there.

Then on Thursday stuck in tailbacks on the M40 southbound the temperature of the car rose from it's normal 'glued in place' 80 degrees to more like 95 degrees. No doubt the standing in the queues was not helping the cooling of a lot of cars.

The car developed a very definate hesitation and then misfiring, not enough to get an engine managemnt light but very noticable.

Today a trip into town and some standing traffic and this time very much worse. Engine light and misfire codes on 1,2 and 3!

Let the car cool and problem goes away, heat it up again and the engine is a dog!
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #12
I have replaced 2 coil packs, the plug leads, fuel filter and one lambda sensor.

No change.

Then yesterday i replaced the other lambda sensor.

I THINK IV'E FIXED IT!
 
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What is a Lambda sensor and where is it and what does it look like? Never mind, googled it, same as Oxygen sensor.

Thanks
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
Discussion Starter #14
I'll try replace the filter and see how that goes. thanks
Something odd with the forum! All these posts credited to me! Not mine! looks like my sign on has been compromised or something!
 
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