[Oli_Marriott]

Hi,

My 1.6 (petrol) Bug seems to enjoy revving itself when the clutch is down. The RPM will drop to about 500, and then the car will rev itself up to 1400-1500 (I assume to stop it from stalling?)

If I let it carry on, it usually goes away after about 30 seconds, and will start idling normally (~900 RPM), but after a period of driving, next time I pull up at a set of lights, it will start hunting again. The problem still happens when the engine has been warmed up too.

Anyway, for the actual question;

I did some code scanning, using a VAG-com, and the results are as follows:

17526 - O2 Sensor 2 - Open Circuit
17549 - Load Calculation Cross Check, Implausible Value
16556 - Fuel Trim, Bank 1, System Too Rich

I'm wondering if they're all related to the O2 sensor, or if there's more likely to be a vacuum leak or something similar?

The engine performs fine, gets between 30-35mpg (without driving particularly economically)

Thanks in advance,
Oli (UK)

 

[billymade]

http://wiki.ross-tech.com/wiki/index.php/17549/P1141/004417

 

[billymade]

http://wiki.ross-tech.com/wiki/index.php/17526/P1118/004376

 

[billymade]

http://wiki.ross-tech.com/wiki/index.php/16556/P0172/000370

http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

One trouble code; seems to indicate a problem with the 02 sensor, which with this particular code definition, typically means it needs replaced. You might remove the sensor; test the plug going to the ecu and the sensor itself, using testing procedures outlined in the service manual. This will require the use of a multimeter. If the test results come up as it being defective/bad (a simple continuity test; will confirm this); then i would replace it with a high quality oem Bosch sensor. If you don't have a multimeter; you should be able to pick up a affordable one; at places, like Machine Mart, in the UK (I'm assuming you live there). You also, might pick up the correct 02 sensor socket; as the tight working area, may require the use of such a speciality tool, most auto parts stores usually sell these as well.

https://www.machinemart.co.uk/

The fuel trim code; indicates a problem and a scan tool with live data, can help you see the fuel trim levels and then, you can go from there (read the fuel trim link for more info).

A common problem with hunting rpm's is vacuum leaks or a dirty throttle body. Removing the throttle body and clean it thoroughly, re-install and run the throttle body alignment, procedure with VCDS.

https://www.google.com/search?q=vcds+tba&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

 

[billymade]

The 02 sensor in question is listed as "B1 S2: Open Circuit"; so, that would typically be the 02 sensor after the catalytic converter.
For specific testing procedures; you need to refer to the service manual, the 1.6L was never installed on USA spec new beetles, so our manual resources are not of any use. You need to refer to a UK specific service manual; like those, from the Haynes UK publishing division.

 

[billymade]

This manual can be purchased online from amazon uk or on the haynes uk site in a paperback format or with access online through on demand, on haynes website.

https://haynes.com/en-gb/

https://www.google.com/search?q=ama...69i57j69i64.4597j0j4&sourceid=chrome&ie=UTF-8

VW Beetle Petrol & Diesel (Apr 99 - 07) Haynes Repair Manual

List Price: £22.99
Format:
Paperback
Quantity

Product description

Complete coverage for your VW Beetle Petrol and Diesel (Apr 99 - 07) T

What's covered:

Hatchback (plus major mechanical features of Cabriolet), inc. special/limited editions.
Petrol: 1.4 litre (1390cc), 1.6 litre (1595cc), 1.8 litre (1781cc) turbo and 2.0 litre (1984cc).

Exclusions:
Does NOT cover Tiptronic transmission. Does NOT cover 2.3 litre V5 engine. Diesel: 1.9 litre (1896cc) turbo, inc. PD.

More Details

Part number:
3798

Dimensions:
270 x 210mm
ISBN-13: 9780857336545
ISBN-10: 0857336541
UPC: 699414003716
Publication date: Wednesday, 10 July, 2013

 

[Oli_Marriott]

Thank you for the comprehensive response Billy! Ross-Tech is certainly an invaluable resource.

I'll take a look at the connector at the sensor end, I believe it is housed under a plastic cover underneath the car, much like the US models. I've got a Haynes manual coming, so I'll take a look when it arrives.


Your work is much appreciated, kind regards from across the pond!

 

[billymade]

Cool, let us know; the results of your 02 sensor testing and how the Haynes manual works for you. Thanks!