SL/R230 Engine problem? - MBWorld.org Forums

Apr 25, 2020 | 10:04 AM

macpooh12

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SL500 R230 Roadster

Engine problem?

Have a ’04 SL500 R230 Roadster - a Florida car, always garaged, well maintained with 78,000 miles. The car was brought up to Massachusetts where it sat for 8 months (garaged). Now that it is back in use, it has developed a “roughness” when accelerating in lower gears but immediately stops once it shifts into a higher gear or when I let up on the gas. It is not a vibration but more like the engine is struggling for a few seconds, although there is no obvious sound of an engine problem. Ring a bell with anyone?

Apr 25, 2020 | 12:31 PM

MBCO

Super Member

Joined: Aug 2017

Posts: 520

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From: Scottsdale AZ

2015 SL550 & 2012 S550 4matic

If you have a scanner check for codes. Perhaps it’s a fuel problem? Was the tank filled and Stabil fuel preservative added? Sometimes condensation can buildup over winter and cause water in fuel that creates ignition issues and codes stored as a result.

Apr 25, 2020 | 01:41 PM

seven_out

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Joined: Feb 2014

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SL500, Miata

Quote:

Originally Posted by macpooh12

Now that it is back in use, it has developed a “roughness” when accelerating in lower gears but immediately stops once it shifts into a higher gear or when I let up on the gas.

I'll speculate this is due to a dirty or failed mass airflow sensor (MAF). The theory is that when you accelerate the engine is abruptly drawing in considerably more air. If the MAF does not signal this change, then the mixture will briefly go lean and cause roughness until feedback from the lambda sensor causes a correction.

I would check the MAF with a $200 Star Diagnosis system or a generic OBD-II scanner which displays live sensor data.