VW Golf Mk5 1.4 FSi CAT query

[TEKNOPUG]

How many CATs on a Golf 1.4 FSi?

I have a rattle from the rear of the car and a P2096 "Post Catalyst Fuel Trim System Too Lean" code. I have it booked into replace the CAT but the garage have asked whether the car is fitted with a rear CAT or one in the manifold? As far as I can see, there is a CAT in the manifold but I can't see one underneath - however, this may be obscured by trim. However, looking at the VW schematics, here http://workshop-manuals.com/volkswagen/golf-mk5/po... it seems to suggest that there is both a front and rear CAT fitted. The rattle is definitely coming from the rear.

Can anyone confirm?

[xjay1337]

One is a "pre cat" basically a cat for when it's cold .
The main cat is further down the pipe.

[TEKNOPUG]

xjay1337 said:

One is a "pre cat" basically a cat for when it's cold .
The main cat is further down the pipe.

That makes sense, thanks.

[TEKNOPUG]

So post CAT, pre CAT, Flexi Pipe and mid silencer all replaced as holed/cracked. Code reset. Runs nice and smooth.

Light back on....

[xjay1337]

Could be a duff sensor. Use VCDS for diagnostics, you should be able to measure live data.

[SMB]

TEKNOPUG said:

So post CAT, pre CAT, Flexi Pipe and mid silencer all replaced as holed/cracked. Code reset. Runs nice and smooth.

Light back on....

I'm guessing you purchased a cheap aftermarket cat, ( vw one will be circa £1000) the error code is almost certainly cat effiecincy failure as the new cat isn't working aswell as the original.

Will come on every time it's reset after the test cycle conditions are met. The cheap cats get you through an mot but that's about it.

[TEKNOPUG]

SMB said:

TEKNOPUG said:

So post CAT, pre CAT, Flexi Pipe and mid silencer all replaced as holed/cracked. Code reset. Runs nice and smooth.

Light back on....

I'm guessing you purchased a cheap aftermarket cat, ( vw one will be circa £1000) the error code is almost certainly cat effiecincy failure as the new cat isn't working aswell as the original.

Will come on every time it's reset after the test cycle conditions are met. The cheap cats get you through an mot but that's about it.

They aren't genuine VW cats but then there is no economic value in spending 4 figures on a £2k car. Fitted lots of aftermarket cats to lots of cars and they've always worked for at least a reasonable amount of time. Will try a few other things first but certainly won't be buying any more VW products.

[SMB]

TEKNOPUG said:

They aren't genuine VW cats but then there is no economic value in spending 4 figures on a £2k car. Fitted lots of aftermarket cats to lots of cars and they've always worked for at least a reasonable amount of time. Will try a few other things first but certainly won't be buying any more VW products.

My experience is that vag based cars use an algorithm that gets upset with the cheaper cats. The cats still work but the car throws an error regularly.

[TEKNOPUG]

The question is do I continue to spend money on sensors etc chasing a fault I may not be able to fix? And how do I sell a car with a warning light I can't switch off?

[shotta287]

My 1.4 FSI was a fault ridden vehicle. For relatively simple basic hatchbacks they are quite troublesome it seems.
If I was in your position I'd sell the car explaining why the EML is on, and provide proof of cats being changed etc maybe a vcds log of the fault too. Not that your average buyer would understand.
Or maybe try posting it for sale on VW/Golf forums?

[TEKNOPUG]

My neighbour had a 1.6fsi and that seemed just as flaky. Fsi system seems a poor design. This hasn't done much to dissuade my opinion that VW are the Apple of cars; their reputation for quality doesn't match reality or justify the expense.

[xjay1337]

SMB said:

My experience is that vag based cars use an algorithm that gets upset with the cheaper cats. The cats still work but the car throws an error regularly.

How on earth can you use an algorithm to determine that?
They are plugged into basic sensors that often use a voltage range.

It's not VW's fault 70% of aftermarket parts are cheap crap.

The 1.4 and 1.6 FSI has a few problems. By and large most VW's are reliable and given the numbers sold most 1.4 and 1.6 FSI's are as well

You have three options

1) take the cat off for a refund
2) buy a cat from a breakers yard (this is what I would have done??)
3) live with the cat as it is, however take the car to a decent tuner who can kill the DTC for the cat code.
3 would probably be the easiest option.

[SMB]

xjay1337 said:

SMB said:

My experience is that vag based cars use an algorithm that gets upset with the cheaper cats. The cats still work but the car throws an error regularly.

How on earth can you use an algorithm to determine that?
They are plugged into basic sensors that often use a voltage range.

It's not VW's fault 70% of aftermarket parts are cheap crap.

The 1.4 and 1.6 FSI has a few problems. By and large most VW's are reliable and given the numbers sold most 1.4 and 1.6 FSI's are as well

You have three options

1) take the cat off for a refund
2) buy a cat from a breakers yard (this is what I would have done??)
3) live with the cat as it is, however take the car to a decent tuner who can kill the DTC for the cat code.
3 would probably be the easiest option.

if you think that the ecu just takes one reading and determines if there is a fault or not then clearly you have a simplistic view on engine management. The ecu will take a range of readings across cold start performance, motorway speeds and heavy and light throttle. Only then will it ping an engine code. If you satisfy those within a day it may set the code same day, or may set the code days/weeks later but it will eventually set the code. That comparison isn't just a single voltage. I don't disagree that the cheap cats are just that , cheap

Edited by SMB on Tuesday 9th January 11:58

[TEKNOPUG]

xjay1337 said:

SMB said:

My experience is that vag based cars use an algorithm that gets upset with the cheaper cats. The cats still work but the car throws an error regularly.

It's not VW's fault 70% of aftermarket parts are cheap crap.

It is their fault that they are charging £1200 for a pair of consumable items on an otherwise cheap and basic car. They've effectively rendered the car an insurance right off for all intents and purpose.

[TEKNOPUG]

I'll fill the tank with Super, reset the ECU and then get is emissions tested. If it passes, I'll assume that there are no other underlying issues apart from the CATs not satisfying VW's coded error parameters.

[TEKNOPUG]

Quick update, put a tank of Super in and the light went off. Also reset the ECU. Light hasn't returned in 200 miles of driving so far.