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1999 Mercedes SLK230 P0204 P0170 P0304 Misfire: Intermittent Cold Start Issue

Model: 1999 Mercedes SLK230 Fault Code: P0170 Posted: 2014-09-03 08:27

Hi everyone, I've got a 1999 Mercedes SLK230 that exhibits an intermittent starting issue when cold. After sitting for several days, the car starts only on three cylinders. Once driven for 8 to 10 miles, the misfire persists but then resolves — after leaving the vehicle off for 20 to 30 minutes, it starts and runs smoothly on all four cylinders. The OBD2 diagnostic system shows three fault codes: P0204, P0170, and P0304. All point to misfires, but I'm confused as to why the issue resolves itself after a period of inactivity. Any insights or troubleshooting steps for this specific combination of codes on my SLK230? Thanks in advance.

Related fault codes
P0170P0204P0304
Comments (2)
Anonymous 2014-09-04 06:44

The P0204 code suggests an issue with the fuel injector on cylinder #4, and given the intermittent nature, it's likely a wiring or connector problem between the Powertrain Control Module (PCM) and cylinder #4's injector. Check for frayed wires, loose connections, corrosion, or physical damage in that circuit — especially when the engine is cold and under low load.

Anonymous 2014-09-08 10:50

Thanks Mohawk — I've already inspected all wiring and connectors, and they were fine. As a next step, I removed and cleaned all injectors, particularly cylinder #4. After that, the car runs normally without any misfire or code persistence. The issue appears resolved.