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After a while the car begins to miss and the dashboard fault…

Customer Question
Hi.After a while the...

Hi.After a while the car begins to miss and the dashboard fault shows - 18 d. When it has cooled down the miss has gone.

Mechanic's Assistant: How long has this been going on?

I have not long purchased it but the documentation I got with it shows its been going on for some time....maybe years

Mechanic's Assistant: What is the model/year of your Mercedes?

Its a 1996 R170 SLK 230

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

No. Not doing myself ...BUT..the mechanic replaced the MAF last week and it has improved the "power" howerer the missed returned not long after I left the workshop

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Only that plugs, plug leads and related bits have been replaced. The carby body also has been replaced.

Submitted: 8 months ago.Category: Mercedes
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Answered in 3 hours by:
11/26/2017
Mercedes Mechanic: Matt, Engineer replied 8 months ago
Matt
Matt, Engineer
Category: Mercedes
Satisfied Customers: 23,441
Experience: Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
Verified

Hello

something to check 1st is the K40 relay unit as its a well-known cause of starting, idling, and engine stumbling problems. This unit provides voltage to the control modules and electrical components, including the fuel pump, electric air pump, and horn. When the K40 malfunctions, these components don't get their required voltage.

Troubleshooting should obviously begin with any diagnostic trouble codes (DTCs), followed by checking for blown fuses. If those lead to dead-ends, the K40 is worth scrutinizing.

The K40 relay is located in the control module box, under the hood. In left-hand-drive R170 SLKs, this box is near the exhaust manifold. A heat shield and a blower motor keep the electronics in the box cool. A non-functioning blower can be a root cause. With the ignition switched on, this fan is audible, and airflow should be felt with the control module's cover removed.

see the attached image for an image of the unit

they can sometimes be repaired by resoldering the joints

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Mercedes Mechanic: Matt, Engineer replied 8 months ago

Hi
do you still need help?
Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! If you're not pleased, also let me know because rating bad does not result in a refund, there are better options. Rating now will not close this post nor prevent further replies
Thanks Matt

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