too much O2 in exhaust gasses

[prelude]

It may come as no surprise, driving a 4.6 V8, that I do not care that much about the environment. Don't get me wrong! I won't destroy it on purpose etc. absolutely not, but I like my big engine and enjoy using it and the consequence of more exhaust gasses does not bother me.

The government however thinks differently :) My last MOT I had quite a job getting the exhaust gasses down to acceptable levels. Turns out that one of my lambda probes had failed, overfeuling one bank permanently. The continues flood of fuel has damaged the bank 1 cat burning it to a crisp.

So, after a lot of repairs and money I hooked it up to the gas tester again and... 8% O2 in the exhaust gasses, throwing the lambda of the scale. As it turns out there is a seal around the small axle that opens and closes the throttle valve that let in air. I replaced all the hoses, seals, clamps and whatever I could find that comes after the MAF sensor, even replacing that thing but I still have 0.87% O2 in the exhaust gasses. The engine is 1 year old and so are all the gaskets, the exhaust is stainless steel so no holes have rusted through.

I am at a loss a to what this can still be. I made the MOT -just- but damn, all this environmental stuff is complex to get right!

Bottom line: if you have a similar problem, check the seal :)

Any suggestions as to where else air can be sucked in after the MAF are welcome

Cheers!
-P

[Scouse]

When emissions were first looked at here years & years ago, a few manufacturers went down the air pump route. I'm not saying its the right thing to do with your P38 and it might not even suit a cat convertor system but it might be a last resort option if everything else has been done/looked at.

Some details here:
Secondary air injection - Wikipedia (https://en.wikipedia.org/wiki/Secondary_air_injection)

[PhilipA]

I think that the measure is of CO. ( unburned hydrocarbons)

Usually with closed loop systems once the engine is warm, the system will run at near stoichiometric and be OK for CO.

I can remember the hints from long ago which include to go for a hard run before presenting for testing and ensuring the car is completely warm.

Thought, What is your thermostat doing? If you have too cool a thermostat ie 82C the engine may still be in enrichment mode or may still be in open loop.

Regards Philip A

[Pedro_The_Swift]

naw,, fuel loop changes at 50 something,, (On the same year D2)

[TheTree]

That's a good tip about the spindle seals !

Part numbers
AUD3577L
ERR4318

Steve

[PhilipA]

I should think that as far as cams are concerned the gems and thor are the same? In any case in my gems I have a piper285 and a tornado chip. afaik it should fit the thor as well. More mid torque and more high end power. The only real downside is a slightly rougher idle, but since the P38 is an auto box, you won't notice it unless the engine runs in park or neutral (unloaded)
I think there is your answer to unacceptable emissions.
Regards Philip A

[prelude]

Thank you all for the tips :)

down here at idle only co needs to be measured and it is well within parameters. We do also need to measure at a higher rpm. Usually 3krpm but for a handfull of cars there is an exception and there is one for the rover V8 as well :) we only need to go up to about 2400. The CO is well within bounds but the O2 effectively means (normally) unused air and would suggest the engine runs lean or somewhere "false" air get's into the system and that screws up the lambda, which needs to be between 0,97 and 1,03. I made it this time but I need to find the source of that air.

Regarding the different cam, I can see that if the cam timing would be too high it would possibly allow air in or smth? Last year when the cam was already in, before my big trip to the north cape, it passed the MOT without to much hassle so I am suspecting a different source of the problems.

I do indeed blast over the local industrial park a few times to get both the engine and the cats hot :) The thermostat is fine according to the engine management system. The only value that is quite a bit of is the air intake temperature. I'd say by about 10c. I guess that's the sensor that sits in the air filter box, right?

Cheers,
-P

[Pedro_The_Swift]

My tornado (Thor) idles at 750,, AFAIK its to do with having the gearbox engaged?
I actually thought the rad end of a thor cam was different too,,,

what do you mean by cam timing too high?

too advanced?

[bee utey]

There could of course be a leaking inlet manifold gasket. New gaskets relax after fitting and should be checked at least once after installation.

[prelude]

The intake manifold gasket is a good thought, I'll check that when I get the chance.

With timing I mean the duration that the intake and exhaust valves are open. Since my camshaft is not standard it could be that the open and close timings are a bit to aggressive and maybe allow some air seeping in? I know a bit about cars and engines but this part is not my strong suit :)

cheers,
-P

[Scouse]

It's not so much valve duration but valve overlap. A 'hotter' cam is designed to work better higher up the rev range but is less efficient down low due to a bigger overlap. You'll be getting some of the inlet mixture going out the exhaust valve at idle.

[prelude]

I was out with the flu for bloody week. Anyway, I just picked my P38 up and I noticed that the engine will simply stall when I come up to a crossing (for which I need to stop). Getting the engine going again is very difficult, flat out floor the gas during cranking and it will very cautiously stumble back to life. So now I drive around left foot braking to keep the revs up.

I just can't bloody understand where this sh... is coming from?! I bought this engine new from RPI last year, it never ran perfectly at idle but I was warned for that due to the cam. It passed the MOT last year with a new set of cats (the old ones having been burnt out by the old rubbish motor). This year has been a whole set of problems ... again. lamba sensors, spindle seals, etc. I finally got it to pass the MOT just barely and now the engine won't run properly at idle. :soapbox:

The missus is beginning to doubt my sanity for keeping such a car around and I am beginning to loose my mind over all these little snags. I am hoping the ECU will learn itself in over time to compensate for all this but if not, I am at a loss what to do next.

Oh the joys of owning an english car :)

-P

[Keithy P38]

Sounds to me like a vacuum leak.

No leaks in the intake system after the throttle body?? Or even something as basic as a spark plug/injector (or multiple) not seated properly?? A vacuum hose from the PCV valve?

Cheers
Keithy

[prelude]

I have redone all the PVC hoses and clamps, replaced the intake pipe clamps etc. I used a fog machine and a compressor to put overpressure on the entire intake system and checked to see where smoke would escape and fixed all those spots one at a time. I now have less then 1% of o2 in my exhaust gas. I am hoping that the auto learn function of the ECU will take care of the idle problem else I will have to take things further apart :(

I am planning on installing a pvc catch can since WAY to much oil (vapour) ends up in the intake. I allready got myself one of those MANN thingy-me-bobs that are widely used on diesels. But first, I'll sort this out :)

Cheers,
-P