Hello - just been browsing forum for answers but couldn't find anything (doesn't mean it's not there somewhere) so I thought I'd sign up and ask directly.

2002 1.9 diesel estate engine performance has dropped right of recently (gradually). No smoke or noise and still starts, idles and runs smoothly it just lacks power and accelerates slowly. I can barely get up to 70mph on the dual carriageway. Tyre pressures are ok. Fuel economy unchanged.

Any thoughts? What should I check?

Thanks.

Fault codes.

MAF or CTS would be my first guess, without any fault codes to guide us.

Try unplugging the MAF and driving the car (this might throw an additional fault code though)

Thanks for the prompt replies.

Just pretend for a second that I do not know how to obtain a fault code and do not know what a MAF or CTS is...

Belive it or not I am fairly competent - but I'm normally rebuilding aircooled VW's

Thanks.

MAF (and n75) locations:

CTS location (110TDI):

Fault codes can be read off using VAGCOM / VCDS or a handheld reader, or even an android based mobile with a Bluetooth ODB2 adapter. The interface socket is located underneath the steering column.

A new CTS and o-ring is about £25 from a dealer (don't be tempted with cheapo ebay copies). The latest generation of CTSs are green, rather than black. They have 4 pins - 2 which feed into the ECU and 2 which control the gauge on the dash. They seem to quite often fail on the ECU side.

The MAF (Mass Air Flow) sensor can simply be unplugged then try driving the car. The car will revert to a generic airflow "guess". If you see a marked improvement then then it is likely the MAF is borked. Replacement MAFs (Bosch or VAG dealer) are quite expensive. Be aware that unplugging the MAF is likely to cause a fault code, so if you have the car checked for faults later by a garage make sure they are aware of what you have done, otherwise they might mis-diagnose the problem.....

Edited 19 September, 201213 yr by mbames

That's great - thanks for info. Will set about working it through...

my bet is maf, air filter may be choked too.

Is your coolant gauge erratic up/down alot?

Edited 19 September, 201213 yr by Lofty79

mine is yes