Duped? 2.0l 16v 9A emissions fail - Cat vs Lambda

[mjcp 0]

The C failed its MoT on emissions today (I think I remember: CO is 0.6, needs to be 0.3), the other readings are in acceptable ranges. Its been running rich for a bit so not too surprised (Poor low speed mpg, good on long runs). Vag com suggests (iirc) 587 - mixture out of adjustment. Its also developed a rattle in the past couple of months - I thought it was heat shields. (car is '94 with 92K. lots of history but probably the original cat)

 

Anyway, garage calls to give me the good news, recommends a new cat at £88 + fitting, OK I say....:shrug:

 

But now I am wondering.... was I rash, would a duff Lambda show up on the Vag com? Would a duff Cat cause a high CO reading?

 

I suppose I needed the cat anyway as it was sounding a bit pants, but my fear is that I'll end up needing a lambda anyway and I could have saved the cash on the cat for next month.

 

hey ho... any suggestions for the negotiation over rates for the lambda fitting ;-)

 

mjcp

[dragon green 4]

A few years back,mine had the same trouble,but was getting really thirsty !

Cat changed, emissions sorted,fuel consumption up,and that annoying rattle at slow speed,especially when reversing gone !

[mjcp 0]

A few years back,mine had the same trouble,but was getting really thirsty !

Cat changed, emissions sorted,fuel consumption up,and that annoying rattle at slow speed,especially when reversing gone !

 

maybe all is not lost then!

 

I don't see how the new cat will affect the thirst/idel though, the Lambda is before the cat (according to Vagcat's diagrams) so how is the effect of the cat fed back to the ECU?

 

Thinking about it, my old 16v KR golf would run 36+mgp doing similar journeys, I struggle to get in 30mpg with the 16v 9A C... perhaps it is thirsty and I've never noticed !

 

mjcp

[daleyboy 0]

Your lambda is really a service item as it does degrade and get slower over time, so i would be tempted to change that as well.

 

I cant see the cat having anything to do with mpg only emissions, but the lambda is a very different story as it controls the AFR......

[mjcp 0]

Thanks for the responses!

 

Well the CAT did correct the emissions with no other work required but it has made no difference to the MPG.

 

Its back at the garage today for a new lambda so we'll see what effect that has.

 

Cheers,

Marc

[davidwort 0]

I'd get your injectors checked, if they are original and over 80K miles they may well have pretty poor spray patterns and this really affects idle and part throttle fuel atomisation and efficiency. Worth getting the fuel filter changed and system pressure checked to. The cheapest generic lambdas don't seem to work very well on the 9A either.

[mjcp 0]

Its a Bosch one going in... Idle is OK, no hunting or lumpiness but will enquire about injector testing (I don't think they have the kit).

 

Marc

[davidwort 0]

injectors are pretty easy to check, they're just pulled from the head and sprayed into jars by jumping the fuel pump relay pins on the fuseboard whilst lifting the air metering flap to open the fuel delivery valve, no special tools needed, just observation of the fuel spray cone and measuring the amount of fuel delivered in one minute to all four injectors.

 

fuel pressure needs a standard fuel pressure gauge, but the correct attachment unions for the k-jet banjo fittings.

[mjcp 0]

The old Lambda:

 

Tip: (slight damage to the very tip when removed)

 

and with cable:

[davidwort 0]

and how is it running now with the new one?

[mjcp 0]

Only driven a few miles today but idle seems more steady and it feels slightly more responsive... could be subconscious I guess. I have reset the trip computer so I can monitor it.

 

Interestingly - the old one was date stamped 2/94 ! So the original one fitted.

[davidwort 0]

Only just changed a 150k one on my 8v too, pretty good considering lambdas have improved over the years too