ricke666

Hi there,

since I bought the car, I was not impressed by the performance. Today I raced a car like mine, and he passed waaay before me. So now, I am pretty sure something goes wrong.

Clues I have right now :
- I frequently have this DTC code : 16804 - Catalyst System: Bank 1: Efficiency Below Threshold --> P0420 - 002 - Lower Limit Exceeded
- When I push the gas to the floor, the "kick" of the turbo is weak
- It seems that the computer wrongly computes the remaining KMs to empty tank (when I put some gas in, computer display eg. 200km remaining. Only 30km farther, it indicates something like 130km to empty!!)

Since I don't have a dyno, what are my possibilities to troubleshoot that?

How can I hope to chip the car if even stock, it is not at maximum power??

Info on the sick audi :
2002 A4 Quattro
213,000km
frequent 16804/P0420 code that comes back when cleared

Any thoughts on that?

a4rob

16804/p0420 means you need a new catalytic converter. Its not an 02 sensor or anything like that. I had the same code happen to me.

In most cases this isnt a big issue at all because all the cat does is help filter bad emissions due to our laws. The only time you need to replace it will be when you do emissions testing.

The little honeycomb pockets inside the cat could have melted quite a bit and are restricting air flow but I doubt its that bad.


In all honesty you have an Automatic 1.8t. It's not a fast car by any means and its not going to feel fast.

Were you racing against a 3.0? Also you could have been racing against a chipped 1.8t or something along those lines.


Change your spark plugs and your engine air filter and see if that helps.

If you have any sort of boost leak in your system then that will cause an under productive turbo.

try this DIY boost leak test to see if that is your problem.

DIY: ALL 1.8T - Boost Leak Tester

ricke666

Ok first of all thanks for the link. I bought the material to test any turbo leaks.

Since cat is faulty but not the cause of the lack of power, I will not focus on it right now.

The car that passed me was a Jetta TDI 1.8T, same power as my car. Chipped or not, I don't know, but it's not the first time that I notice the lack of power.

Now concerning the spark plugs, in my previous car, some types were better than others. What types of plugs are best?

For the air filter, ok, that can be a good idea. I'll go with stock since I don't believe in cold air intakes, well it works a few HPs, but it is not worth the few hundred of bucks. I remember my 2002 civic, at that time I've had my intake for under 70$...

I'll be doing the leak test some time this week in the mean time!

Thanks for input!

a4rob

there is no jetta tdi 1.8t from my understanding. It was either a tdi or a 1.8t and yes the 1.8t engine is the same however i highly doubt it was a tdi that beat you. Their engines are around 100 hp and 177 torque.

The reason it beat you is because the jetta 1.8t is lighter then our cars, you will lose to one every time. Our cars are much heavier.

the oem filter is best for this car. Its been proven that after market intakes and filters dont provide more HP with the 1.8t

The spark plug everyone seems to get the best feedback with is the NGK BKR6E. Its a copper plug so you will have to change it more often then the plugs in your car right now. Its very easy to change them, takes 10-15 minutes so its no big deal.

Tim$2

Could have been an '04 Jetta 1.8T. I think they were up to 180hp weren't they? ... and lighter. The only TDi's that would have a chance would be tuned older ones or the newer CR's They have a lot of torque but top out pretty quick. 140hp/238lb.ft I seem to recall.

gurvir44

Try Sea Foam. I tired it and big improvement. But you gotta change engine oil after.
Sea Foam Usage Video
B5 A4 1.8T: How-To Sea Foam

jordon

iTrader: (1)

OP: if your cat is clogged, it could indeed cause a loss in performance... when a cat becomes clogged, the problem will get progressively worse- slower spooling of the turbo, less boost, etc.
i would follow what A4Rob said, but since you know you need a new cat anyway, why not either get a new one, or get a testpipe, and chip the car... you can get the tuner to code out the cel for the cat at the same time!
good luck!

ricke666

Concerning the test pipe, didn't I hear in the past somewhere that doing that causes a pressure loss in the exhaust and that is bad for the turbo? Or maybe that was concerning my old car with a supercharge...

Also, doesn't that fire up a check engine DTC error?

Would a cat from eBay, like this one, be a problem somehow?

If I go for the test pipe, will I be kicked out of drive-in theaters because of the smell??

a4rob

test pipe will fail emissions if you have to pass them in quebec.

jordon

iTrader: (1)

Turbos do NOT like backpressure... A testpipe will only improve performance.
Yes you will get a cel/dtc if you get a testpipe, that is why I said to chip it, and get the tuner to code out the secondary O2 sensors- then no codes!
As for eBay cats: that is up to you, my friend.
Smell: yes, the exhaust will smell a little different. Enough to get kicked out of a drive-in? Only if they also kick out people in busted *** chevy's etc from the 80's and 90's lol!