When stopped at lights, engine surges and almost kicks foot off brakes
06-28-2018, 08:26 AM
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1998 C200 Elegance
When stopped at lights, engine surges and almost kicks foot off brakes
Hi folks.
Total newbie here.
The problem I have with my 1998 C200 sedan (131,000km) is that when stopped at the lights with the transmission in drive, intermittently the engine RPM drops in a fraction of a second from 700 idle down to 500, then straight back up to about 900 in another fraction of a second before settling back to idle. Sometimes it happens only once, sometimes 3 or 4 times in the space of 10 seconds.
What's worrying is that when it does it, and the engine appears to surge and it seems to put energy into the transmission and the car tries to drive forward for that fraction of a second. I have to keep my foot very firmly on the brake pedal.
This all started happening about 10 months ago, along with lots of backfiring and some loss of power. At that time my local mechanic replaced the MAF and spark plugs, and cleaned the PCV valve (which he said was very dirty). It ran well for about a month, then the surging began again.
I had just been putting up with it since then, but as the car was due for its service last week I asked them to take another look at it. They say they took it for a drive, and couldn't replicate the problem (possible if they didn't drive it very far, as it is intermittent). They say there are no error codes. They did clean the throttle body, and the car certainly has more power now. But the surging continues, and one or two backfires here and there.
I've read posts on the forum about MAFs, but it has a new MAF. Could it have been installed incorrectly, or come loose or something? Could it be the engine mounts that I have read about -- but would that explain the surging forward problem? The coils haven't been changed -- would that help?
Or could it be coming from the other direction -- a problem with the transmission?
Any ideas you might have would be greatly appreciated.
Thanks in advance.
John
Total newbie here.
The problem I have with my 1998 C200 sedan (131,000km) is that when stopped at the lights with the transmission in drive, intermittently the engine RPM drops in a fraction of a second from 700 idle down to 500, then straight back up to about 900 in another fraction of a second before settling back to idle. Sometimes it happens only once, sometimes 3 or 4 times in the space of 10 seconds.
What's worrying is that when it does it, and the engine appears to surge and it seems to put energy into the transmission and the car tries to drive forward for that fraction of a second. I have to keep my foot very firmly on the brake pedal.
This all started happening about 10 months ago, along with lots of backfiring and some loss of power. At that time my local mechanic replaced the MAF and spark plugs, and cleaned the PCV valve (which he said was very dirty). It ran well for about a month, then the surging began again.
I had just been putting up with it since then, but as the car was due for its service last week I asked them to take another look at it. They say they took it for a drive, and couldn't replicate the problem (possible if they didn't drive it very far, as it is intermittent). They say there are no error codes. They did clean the throttle body, and the car certainly has more power now. But the surging continues, and one or two backfires here and there.
I've read posts on the forum about MAFs, but it has a new MAF. Could it have been installed incorrectly, or come loose or something? Could it be the engine mounts that I have read about -- but would that explain the surging forward problem? The coils haven't been changed -- would that help?
Or could it be coming from the other direction -- a problem with the transmission?
Any ideas you might have would be greatly appreciated.
Thanks in advance.
John
