peh-amg

When I'm cruising on the highway at 70-75 and then gently accelerate the engine does not accelerate smoothly - it feels like multiple misfires - about one second between them - nothing violent and no strange sounds but can clearly be felt. However, if I step on it and it drops down a gear or two it's fine.

Any ideas what is causing this? Fuel? Spark? Other?

Stangely enough my last C63 ('09) also did this occasionally and my dealer could never identify the problem.

Pit-Pony

Misfires will throw a code.

peh-amg

I agree it should - I'll have to get the dealer to check.

What else could it be? Maybe it's some sort of hestitation but what could be causing that?

drawde

sorry to hijack..

I had something weird happen the other day, not sure what it was but i was driving regular for a bit then tried to pass this one guy so i was accellerating a little and when i took my foot off the gas, the rpm's stayed high for a while (like i was supposed to upshift) but i was in sport-auto mode. the RPM's did not go down until i actually pressed the brake. i've never had that happen before, is that bad or normal?

Mort

Throttle sticking? Check your floor mat and anything else that may jamb in or under your throttle pedal. It could also be something holding your throttle blades open like a sticky control motor linkage or cruise control glitch. So many electronic interfaces on these cars. May be nothing to worry about if it does not happen again and near impossible to diagnose without any existing symptoms.

Mort

Too much load in too high a gear and the throttle response can lag and feel like a hesitation. Try more pedal or click it down a cog.

hhughes1

Prior to having a severe misfire issue that is documented in another thread, my car would on occasion sputter for a second while accelerating at half to three quarter throttle. This began about a month before the serious issue started and occured every few days while the car was still warming up. After replacing an 02 sensor and installing new plugs (the four on the problem side were completely fouled) I have not had this issue again. I think it was the first signs of the problem that was developing at the time.

PS: This sputter occured after 3 or 4 seconds of accelerating, it was not a hesitation as you step on the gas issue. Felt a lot like a fuel starvation problem but corrected in an instant.

peh-amg

Mine feels like fuel starvation or lack of consistent spark - it's a mild quick hiccup every 1 or 2 seconds as I gently accelerate from 70mph on the highway in 7th. If the car kicks down a gear I don't feel it.

Merc63

Check your spark plugs

peh-amg

Car only has 2,500 miles on it. Wouldn't it do it all the time if it was plugs?

Muskoka_AMG

Probably, but why not check the easy and cheap things first. Many of members on here have wasted a fair amount of money because they didn't check spark plugs first.

peh-amg

Good point.

Merc63

No, it could have recently happened from bad fuel or something else.