Date registered: Feb 2011
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Start-up issues - pedal vibrates / pulses ('97 C230, 160K miles)
I have a 1997 C230 with about 160K miles and has been very well taken care of.
Recently, when I turn the car on, about 60% of the time the "check engine" light is on and the pedals vibrate / pulse pretty violently, to the point that your whole body is pulsing when your foot is on the pedal. It may be only the brake pedal that is pulsing, but it's hard to tell because the pulsing is so strong. The car can still drive when it does this, but I'm worried about safety so I don't drive it.
When I turn it off, wait, and turn it back on, sometimes it will stop. Other times that doesn't work and I have to turn off and restart again. Sometimes even after the pulsing goes away, the "check engine" light is still on (and other times it's off). At night, I keep the car in a garage, so it's usually around 50 degrees when I turn it on (despite the cold weather in DC).
Once the car has been driven for a while, the issue doesn't come back. It really only happens when it hasn't been driven for a couple of hours.
I brought it to a mechanic who hooked it up to the check engine reader thing (sorry, I don't know what this is actually called), and it said that something misfired (piston maybe? something having to do with start up). He changed the spark plug wire set and the problem went away for a couple of days. I hadn't driven it for the last 4 days, but now it is back.
Does anyone know what this is, how serious it is, and if it is a safety issue? I love my car and am willing to pay the money to fix it if it is necessary and relatively reasonable. Thank you for your help!!