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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53902
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Cold idle is too slow ... engine idles rough and frequently

Customer Question

Cold idle is too slow ... engine idles rough and frequently stalls ... how can I speed it up?
JA: How many miles are on the car? Have you checked the spark plugs?
Customer: 113,000. spark plugs are nearly new
JA: What is the model/year of your Mercedes?
Customer: 1982 SL 380
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Yes ... I have looked for an adjustment screw but haven't found one
JA: Anything else you think the mechanic should know?
Customer: It runs smoothly once the engine is warmed up
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mercedes Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, the SL uses an idle speed valve and control unit. There is no idle speed adjustment on this car. To increase the idle speed you can clean the idle control valve and clean the throttle body. Aside from that you will need to replace the idle valve and control unit to increase the idle speed. Keep in mind that the normal idle speed for this car is 650 rpm in neutral and 500 rpm in drive. One trick that you can use to fool the system is to disconnect the oil temperature sensor on the oil filter housing. This will raise the engine rpm approximately 100 rpm.

Let me know if you have any questions. Please rate my service in order for the website to credit me for answering your question.


Expert:  Marty replied 1 year ago.

I'm just following up with you on this question. You never rated my service therefore I never got paid for answering your question. If my answer was helpful I would appreciate it if you would rate my service so I can receive credit from the website.