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Hi, all last weekend the car started reving a bit strangely, went out for the day did about 50 miles on the motorway and when i got back the revs were bouncing between 1100 and 1300 rpm.i had it on vcds and it came up with 02 sensor
Today i have had the 02 sensor done and its still the same, scanned it no fault codes, also since i got the car while driving when you take your foot of the accelorater the rev do not drop off straight away it will keep reving for a second or 2 before dropping off can anyone shed any light on this, ive checked for air leaks cant find any ive given the throttle boddy as good a clean as i can without taking it of the car. any help please before i have to take it to a garage
 

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Hey, please fill out your profile info (car, year, model, engine, trans, where you live etc.); that way we can help you more intelligently! :)

FUEL DELIVERY:

My first thought; would be a fuel delivery problem. Since you cleaned the throttle body; did you do a throttle body alignment process with VCDS?

Throttle Body Alignment (TBA) - Ross-Tech Wiki)

I would also; check what your tirm levels are at. This can pinpoint; the two typical issues, related to that when the trim levels are out of whack: e.g. bad maf or vacuum leaks. To quote Ross Tech:

In general, an out-of-spec value in the first field (Additive) indicates a vacuum leak since it is mostly present at idle, when vacuum is highest. An out-of-spec value in the second field (Multiplicative) indicates a fault at higher RPM, and may point to a faulty MAF.

Fuel Trim Info - Ross-Tech Wiki

MAF:

Maf testing; you might pull the plug off of the Maf and see if the issue, goes away. If it does; a Maf maybe the culprit but further testing and troubleshooting is needed to confirm. Cleaning the Maf sensor is a good idea and is a inexpensive first step in troubleshooting the problem. Check out these links for more troubleshooting and testing procedures.

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=jetta maf testing

FUEL PUMP:

I would test the fuel pump for proper pressure; you can typically buy a inexpensive gauge/test here in the USA at most auto parts stores or they will loan it to you for free. Hook it up and see if you are in spec; according to the VW factory service manual procedures, spec info.

Keep in mind; this 1.6L engine was never sold in the USA, so we cannot give you specific indo about it but the troubleshooting principles are the same. Please fill out your profile info and give us all the specifics about your car (miles, year, model, trans, etc.). Also, if you have any scans or trouble codes, from before you had the 02 sensor replaced; please post any scans or info you might have. Start testing and checking out the fuel trims with VCDS, do a throttle body alignment and your fuel pressure, we will go from there! Lets get this thing fixed!
 
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