Hi All,
Just failed my IVA today (see here)
Main fail point was emissions. The lambda is too high (1.180 - should be between 0.97 and 1.03).
I wasn't expecting to see this as I'm using an un-tuned engine (Rover T16) with it's OEM ecu.
Any ideas what could be causing this or how to put it right? The tester suggested it may be down to me using a shorter exhaust than the original donor? He might have a point? Also, could it be the fuel pump struggling a little? Could it be an air leak somewhere? I'm at a bit of a loss.
The engine itself, for the most part is running OK. The only slight issue is when you blip the throttle from idle when it's hot, it sometimes splutters a little - maybe a connected issue?

Cheers,
Bill

Exhaust length shouldn't be an issue as long as his probe was in far enough. Air leaks on the exhaust are the most common cause (air leaks on the inlet side tend to result in rich mixture as the ECU over-compensates). Slide fit joints are poor for this, if you have any seal with silicone. Lambda sensor might also be tired if it's the original and switching a bit slow. If you don't find a leak try a new one but buy quality not cheap as they can be dodgy.

Coolant temp is another favorite for odd fueling issues.

I would second an exhaust leak somewhere too. Good fail though, nice to see someone else using the T16 turbo engine!!






Tony

Sounds like it is running lean.
All of the above but also check the fuel pressure is within spec , if not it is probably a fuel pressure regulator issue rather than the pump.
Clean the small bore pipe out between the ECU and the throttlebody --- very carefully disconnect both ends.
Thermostat is also a possible cause ---- get a 91/92c stat
Temperature sensor for these is quite cheap
I would also have a look at the lambda sensor output to see how quickly it is switching hi to low and back.
Gendan should be able to supply the correct Lambda sensor

Also if the fast idle test was carried out over 2750 rpm it can lead to odd results as some older Rovers go open loop at 2,750.

If you suspect air is getting sucked back into the exhaust (I don't think this the cause in your case) you could tack weld a restriction washer inside the tailpipe

Thanks for all your ideas guys - I'll check through all these and see what I see.

Interestingly, because of problems with the battery, I had a knock on effect with the water pump controller - it's one of those Davis Criag things (bad mistake for me to use these as it's caused all sorts of problems.)
To get round it short term, I bypassed which meant the pump running full speed and meaning the engine was a little cooler than it should be - could be the problem?

The 2750 rpm issue mentioned by britishtrident is also interesting. Pretty sure the test was done slightly higher than that - more like 2900.

Thanks again for your pointers.

Cheers,
Bill

Well, I sorted any possible leaks in the exhaust system and took it to the local garage for a emissions test - Lambda is now perfect score of 1.00

So, IVA re-test booked for next thursday