Passat 1.8 APT engine failing emmissions

[Sam Russell]

My Passat Estate 2000 (X plate) is failing emmissions on low idle.

RPM 850
Engine temp 95
CO 4.20 .................................................. ........................................FAIL Should be less than 0.5
Lambda 0.901
CO2 12.3
HC 209

RPM 2360
Engine temp 95
CO 0.01
Lambda 1.002
CO2 15.2
HC 17

Just replace the lambda probe with genuine VAG part.
No exhaust leak.
I have owned the car from new. It has 57,000 miles on it.
Car runs perfectly, with no obvious faults. Exhaust pipe is spotlessly clean.

Any ideas?

[zollaf]

scan for faults ?

[Sam Russell]

I will try tomorrow if I can get the PC to work.

[Sam Russell]

scan for faults ?

Well I ran the version of software I have, which is not the full version.

No fault cades appear.

Running idle I get

840 RPM 86deg Lambda 0% Bin Bits 11110111 21.8% Load Inj on time 4.1ms Mass Flow 3.64 G/S Load 4.7%
Ign Timimg [This cycles from 1.5 deg ATDC to 2.3 deg BTDC. Cycle takes about 1 or 2 seconds.

Rev the engine and I can feel a bit of vibration like a missfire, but not pronounced and not at idle.

Hope that gives some ideas.

[zollaf]

so, she is rich on idle but ok on fast idle. the cat seems to be working though, but that idle co is far too high, even discounting the cat. when was she last serviced, plugs and air filter ?

[Sam Russell]

The plugs were done recently, together with an oil change. Not sure about air filter.

[zollaf]

well my initial thought is a slight misfire on idle causing unburnt fuel to go into the exhaust, but that should put the hc level up. check the airfilter and also check for any vacuum pipes that may be leaking air into the system. there is more vacuum at idle so would affect idle more.

[Sam Russell]

well my initial thought is a slight misfire on idle causing unburnt fuel to go into the exhaust, but that should put the hc level up. check the airfilter and also check for any vacuum pipes that may be leaking air into the system. there is more vacuum at idle so would affect idle more.

HC level is 209 at idle, but only 17 at high idle.

I will check the air filter and also the vacuum pipes. Thanks for the pointers.

[zollaf]

yep, my bad , can't read. hc is high at revs :), so this indicates unburnt fuel or just too much fuel going in.

[Sam Russell]

yep, my bad , can't read. hc is high at revs :), so this indicates unburnt fuel or just too much fuel going in.

OK, so the high idle is nearly perfect, but low idle is showing unburnt fuel.

I will check the air filter and all the vacuum pipes (if I can find them) and see what that does.

Could it be something simple?

[Crasher]

Co that high at idle should have produced a fault code, it does not make sense that there are no codes shown.

[Sam Russell]

Co that high at idle should have produced a fault code, it does not make sense that there are no codes shown.



Ok, took the car for a run to get it up to temp and let it run at speed/normal driving.

Fault code now showing.

1801 Power supply terminal 30 - Voltage too low

P1602 - 35 - 00

Hope that helps.

[Crasher]

Change the ECU relay in the plenum chamber water box, inspect everything in there (including fully dismantling the ECU plug) for corrosion water damage.

[Sam Russell]

Change the ECU relay in the plenum chamber water box, inspect everything in there (including fully dismantling the ECU plug) for corrosion water damage.

Do you have a VW part number for that relay. The local VW dealer can not find it.

Thank you.

[Crasher]

165 906 381 in the water box with the number 30 printed on top.

[Sam Russell]

165 906 381 in the water box with the number 30 printed on top.

Thank you for that.

Regards.

[Sam Russell]

OK, I got that relay and changed it. There are only 4 wires connected to it. Is that right? No sign of a 5th wire atall.

Bad news (maybe) is that the fault code has now changed to

16947-035 kwp1281
System Voltage too high
P0563

@ Crasher - Have you any idea what that would indicate?

[Crasher]

Check the ECU supply voltage in Measuring Blocks 08, Display Group 004, Display Zone 02. It should be between 12 and 14.5 v with the engine running, not more than 15v. With the ignition on, check the voltages across socket 1 to 3 and 2 to 3 and this should be approx battery voltage. With the ign off check the voltages across pin 1 to 62 and 2 to 62, again these should be approx battery voltage. Have you had a booster pack on it?

[Sam Russell]

The car is as supplied. No mods (apart form this problem) since new. I am the only owner. So, no, it has not had a booster. (By the way, what is a booster pack?)

Thanks for your quick reply.

[zollaf]

have you ever had a flat battery and had to use an alternative way to get it to start ?

[Sam Russell]

Yes I have. I have used jump leads and the mechanic used a box to do the same. I normally wait a few minutes before removing the jump leads. He did not wait any time atall.

[Crasher]

That is what I meant by booster pack....:rolleyes:

Clear the code and see if it comes back.

[Sam Russell]

Sorry, I have never heard that term before.

I will check again but code re-appears as soon as the code is cleared.

[Sam Russell]

I checked just now. Cold engine - start engine - no codes. Rev engine - no codes. Drove a few hundred yards, did a three point turn and returned. Engine not up to temperature. Still no codes.

Is that what you expect.

[Crasher]

See how it goes.

[Sam Russell]

Thanks. I will check again later when the traffic dies down.

Thanks again for your speedy response.

[Sam Russell]

Those two faults pop up alternately. Either voltage too low or voltage too high. Battery gives 14.2 volts with engine running, whatever the revs.

Checked the wires around the ECU and no sign of a fault or corrosion. I have changed that relay (marked '30' on the top).

Could fault be elsewhere? Mechanic suggested a fuel additive might fix it. Is that worth trying? (I do not have an easy way (or any way) of checking the emmissions).

Any ideas?

[Crasher]

I doubt a fuel additive is going to help with an electrical problem

So these two fault still keep coming back? If so it could be all sorts of problems such as a corroded connection or a faulty alternator that you are not seeing when it plays up.

[Sam Russell]

My problem is the emissions failing on low idle. The car is booked in for the MOT next week and it needs to pass. The car runs fine on the road and drives like a new car. The exhaust pipe is gleaming on the inside, so there are no carbon deposits. The lamda reading was .992 at high idle, with CO at 0.21%. The CO at idle is 3.14% with lambda 0.937.

Any ideas of where I can look?

[Crasher]

It could be a faulty lambda sensor as they do not always trigger a fault code but I suspect that the cat is faulty, do you know if it is the original or a replacement? If it is the original I would try a new lambda sensor first.

[Sam Russell]

I have just replaced the lambda sensor with a genuine VAG one. The car only has 57,000 miles on it. Runs OK with normal power. It idles properly.

I am at a loss as to what to try next.

[Crasher]

For the cat to work, the gases before it need to be lambda 1 +/- only a small margin and the lambda sensor you have fitted is saying it is way off. If it had a sample port you could 4 gas before the cat but I don't think it has one, I wish they had not done away with the, probably saved a few Cents.

[Sam Russell]

The lambda reading at high idle is 0.992 with CO at 0.21% When this was fitted, it fixed the Lambda reading from 1.120 to 0.992

At low idle Lambda is 0.937 and CO is 3.14%

The CO is way out at low idle. Should be below 0.5%

I am begining to despair of it ever passing.

[Crasher]

Without seeing it all I can suggest is a new Air Mass Meter but it could be an air leak or faulty (new) lambda sensor, I would have to study some measuring block info to know. If you do fit a new AMM, only buy it genuine exchange from the VW dealer, NO WHERE else!