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Premium Member 2014 SLK55 AMG
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Discussion Starter #1
Ok I have a problem/problems that is/are greying my hair even more.

SLK 320

If the car is left to stand idling ( driveway or a traffic jam ) for a long time the temperature gets to 80, stabilises for a while and then kicks over and slowly climbs to around 95.

1-where is the temperature sensor, how can I test it as I'm not sure the fan is kicking in.

2- can the system get airlocked. How can I bleed it?

The car is not loosing cooling fluids!

After a while at 95 degrees trying to move off the car misses badly. This is always on the right hand bank, cylinders 1 and 2 and if its really bad 3. never seen a report of a misfire on left bank. The longer it stands at 95 the worse it gets.

Turning off the ignition for a few seconds usually clears the missfire for a few minutes at least.

Flooring it hard the car pulls ok but ocassionally, very ocassionally at around 5000 to 5500 it's like the ignition was turned off! Engine does not fire at all, flatlines for perhaps one o two seonds then continues as normal.

I have replaced plugs, coils, maf , both O2 sensors and the crank sensor and although the misfire changes personality a little bit the basic circumstances do not change!

3- could this be valve related? Hot= valves on right bank not seating/opening?

4- any and all suggestions about what to try next accepted! I'm at my wits end!

I have a buyer for my car and I need the driveway space for the '55!
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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97,402 Posts
your profile says 55 and now you say SLK 320

you have 2 slks?
 

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Premium Member 2014 SLK55 AMG
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1,665 Posts
Discussion Starter #3
This week I do! Collect the 55 this coming weekend. Thread here

Have sold the 320 but really want to fix this misfire before I hand it to the new owner!
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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97,402 Posts
That, my friend, is very commendable!
 

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Premium Member
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Maybe try going through the normal stand and idle procedure and allow it to misfire then turn off the ignition and pull the plugs and check how they look.
I'm thinking injectors or overheating fuel in the return line to the tank, perhaps something to do with the fuel pump or electronic injection system. I'm not 100% on the R170 so its a bit of guess work and desperation .
Hope it may point you to some alternatives.
Cobra
 

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Premium Member
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Forgot to add -
My R171 runs at 80 whilst moving but goes up to 95 whilst standing in traffic.
Always has and been told its normal.
My misfire was due to a faulty coil pack.
 

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Premium Member 2014 SLK55 AMG
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1,665 Posts
Discussion Starter #7

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Premium Member 2014 SLK55 AMG
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1,665 Posts
Discussion Starter #8
Forgot to add -
My R171 runs at 80 whilst moving but goes up to 95 whilst standing in traffic.
Always has and been told its normal.
My misfire was due to a faulty coil pack.
Thanks for that.

The more I investigate the more I suspect that my ecu is suffering from a problem I have come across. The coil drivers in the ecu may have a problem.

The fact that the problem goes away, at least for a while seems to point to an electrical problem.

Mob in southampton have quoted £333 for repairing the ecu ( if it's broken ) May just have to come to some agreement with the buyer. :(

Going to try a really coarse test. Have some cooling spray, will get the lot hot with the ecu lying loose and then cool off the ecu, which gets good and toasty!

Maybe just replacing the fan in the electronics box will fix it! :biglaugh:
 
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Premium Member 2005 SLK55 AMG; 2005 SLK350
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Just gussing here, I'm totally unfamiliar with your car or engine:

- A ground issue affecting one bank only?
- Some other electrical component that is "one per bank" (my older volvo has two ignition amps, one for 1-3, one for 4-6).

If you're not sure your fan is running it might be good to make a manual check.
 

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Premium Member 2014 SLK55 AMG
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1,665 Posts
Discussion Starter #10
Just gussing here, I'm totally unfamiliar with your car or engine:

- A ground issue affecting one bank only?
- Some other electrical component that is "one per bank" (my older volvo has two ignition amps, one for 1-3, one for 4-6).

If you're not sure your fan is running it might be good to make a manual check.
The 320 has a coil pack per cylinder and 2 spark plugs per cylinder. not sure that there is only one earth per bank but I'll go have a dig around.

The temperature seems to be standard so it's appears to be just once that heat soaks through to all the components ...... kind of points to the Ecu again.

Ran the car up to 'failure mode' yesterday, got cylinder 1 misfiring. Disconnected the coil from the harness by unclipping the connector, misfire did not change in the least so it looks like that signal was not getting to the coil! Plugging it back on did not clear the misfire.

turn off, turn on and it's gone. but came back shortly.

Disconnect again ( engine off ) connect to spare coil pack with leads and plug attached, start engine, plugs firing cleanly???? One would think a duff coil pack but the one on the engine is the new one!

I am pretty convinced that the ECU coil drivers are on the way out :( :( :( :(

Anyone know what the actual repair is to the output drivers? Replacing mosfets or something?

Just found this .......
SLK (from 1999) C class (from 2002) suffer from 'check engine' light illuminating with PO30/32 codes (misfire). This is caused by defective soldered spur connection in wiring harness (+12V feed to coils). Resolder to rectify.
Anyone know anything about this fix?
 
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