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My car has a kind of a rough idle and it's like it gives a bit of gas, meter goes between 1000 and 2000 rpm at standstill. Same if I shift up to 1 or 2nd gear. If I then take it for a drive, car jerks and jumps as rpm meter goes up and down at low speeds in 1st and 2nd gear.

And it's not like the car dies or anything, it just runs jerky and jumps as rpm meter goes up and down for a few meters, then it smoothens out as I drive.

So if I give a bit of gas and rev up the engine, or drive for 5 minutes, it runs as it should. Or if I just sit idle and wait as rpm meter goes up and down for a few seconds it also smoothens out and seems to be OK. What could be wrong?

Problem seems to be most noticeable in the morning at first start. If I take it for a drive, park it and then drive again later that same day, it's not as noticeable.

We did a diagnostic test a week ago where it said that the MAF-meter needed to be replaced. So we did install a brand new but problem is still the same.

Any ideas?

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One thing thay may be worth a look is the idle air control. –  Ben Neill Apr 26 '12 at 13:12
    
@BenNeill Wouldent that show up on a e-diagnostic test? –  jamietelin Apr 28 '12 at 13:28
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I have had similar on other (Australian) makes of similar vintage. Mercedes may be better with detection, but IAC valves have a reputation of not always triggering an error. –  Ben Neill Apr 28 '12 at 23:11
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2 Answers 2

It could be caused by ignition cables, coils, plugs, I have had the same problem in my Skoda Octavia ´00, in the morning it was like one of cylinders is not having a spark, combustion was very bad and power was reduces but only for max 5 minutes, then after engine got heated a bit it disapeared,

also this problem is related to damaged gasket under the cylinder head when there is not sufficient pressure, it get worse by time. Measure a pressure at each cylinder and you should know better then.

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These motors were plagued by problematic cylinder heads. Usually the end result in cases like yours are replacement of the Cylinder Head. Most likely there is either a blown head gasket or burnt exhaust valve.

If there are no vacuum leaks and MAF is good then you need you start looking deeper into the engine.

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