# 2.0 Rough idle..



## maag himself (Jan 31, 2011)

Have a 2000 Jetta with the 2.0 (AEG). It was suffering from jerky acceleration which progressed and got worse. Now it even idles like crap and then entire car shakes from the rough idle. I read on here that a common cause was the MAF and a good way to test to see if it's the MAF is to disconnect it and see if the idle smooths out.

So I disconnected the MAF while it was running... and the idle smooths out. No more jerky acceleration. Everything appeared golden. So I buy a MAF from ECS Tuning.

I install new MAF and run it.. and it runs like **** again, just like the old MAF. 



What could this be?!


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## ps2375 (Aug 13, 2003)

have you checked for codes? Just installing a new MAF does not clear codes and it will take some driving time for the EC to "adapt" the fuel trims to the new MAF. One way to get a head start on that, is to clear the codes to reset the fuel trims back to zero. Scann ing for codes should be the first step, especially if you have a MIL on.


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## Anony00GT (Mar 6, 2002)

Definitely scan for codes first.

You just learned the hard way that you should diagnose properly before you repair.


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## maag himself (Jan 31, 2011)

Been putting it off for sometime now, but guess its time to invest in a VAG-COM..


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## Anony00GT (Mar 6, 2002)

maag himself said:


> Been putting it off for sometime now, but guess its time to invest in a VAG-COM..


Now you're catching on


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## maag himself (Jan 31, 2011)

So I bought the VAG-COM and scanned it. It initially had these codes:


16795 - Secondary Air Injection System 
P0411 - 35-10 - Incorrect Flow Detected - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected 
P0300 - 35-00 - 
16686 - Cylinder 2 
P0302 - 35-00 - Misfire Detected
16684 - Random/Multiple Cylinder Misfire Detected 
P0300 - 35-10 - - Intermittent
16686 - Cylinder 2 
P0302 - 35-10 - Misfire Detected - Intermittent
16486 - Mass Air Flow Sensor (G70) 
P0102 - 35-00 - Signal too Low
16496 - Intake Air Temp. Sensor (G42) 
P0112 - 35-00 - Signal too Low
17663 - Engine Coolant Temp Sensor (G62) 
P1255 - 35-10 - Short to Ground - Intermittent


So I cleared those codes, and this one reappeared consistently:



16684 - Random/Multiple Cylinder Misfire Detected 
P0300 - 35-00 - 
16686 - Cylinder 2 
P0302 - 35-00 - Misfire Detected


Again, it only runs rough at idle. When it's idling I can sit and watch the misfire detection block in VCDS consistently climb at a rate of like 1-2 per second, or more. Give it a little gas, and the misfiring stops. It's probably worth mentioning that I have this engine tick which sounds very much like a dead/sticky lifter. Could that be possibly causing the cylinder misfire? Or maybe the misfire is causing the ticking somehow?

Anyone have any ideas where to start to look to isolate this problem, before I go throwing more parts at it like a knucklehead?


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## Anony00GT (Mar 6, 2002)

Check spark plugs, wires, coil.


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## sick50racing (Jul 28, 2006)

this sounds identical to my problem im having, even the same ticking!! I have thrown parts at it left and right with no better result. Replaced MAF, CTS, checked vacuum leaks, took apart airbox and changed filter, checked timing, etc. I have yet to change the plugs, wires and coil but I think thats next! I have NO CEL what so ever.:banghead: Keep me posted if you figure it out


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## Anony00GT (Mar 6, 2002)

CEL or not, get scan data. Codes and fuel trim info to start.


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## Bon3 (May 9, 2013)

Def. The spark plugs or coils!!


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