[alfizta]

I'm trying to nail an air leak. I'm convinced of it. But not sure where it is. Intake or exhaust...

ECU has been able to adapt by at least changing TRA parameter to the lowest limit. p1172 pops, then engine runs almost perfect. Idle jumps once in a while, could be pullling better, but goes well on emissions. Lambda is OK! MAF too.

Have reset TRA parameter, ECU still adapting, so I'm getting always Lean condition on bottom limit.

I'm thinking that if I have an exhaust leak lambda sensor will always get too much oxygen, so it would be impossible to get nice lambda graphs like I'm used to get. Intake air leak, then. Am I right?

But, anyway, is it possible for the ECU to adapt to an exhaust air leak?

THANKS!

 

[gazza82]

P1172 is the throttle potentiometer ...

And don't always believe the lambda is ok. If it's not a Bosch is could be the wrong impedence .. Bosch is 8 ohm, NTK I think is only 4. I had the latter fr a couple of years and gave nothing but issues at emissions tests and it was always running too lean. I put a Bosch in (universal LS615) and it's been great since. Last mot in June reading was zero on CO emissions on fast idle!

 

[alfizta]

thanks, Gazza! but still haven't got my answer

 

[Leaky 156]

I'm no expert, but the ECU responds to info from the sensors/probes. As I understand it the lambda will be making adjustments 'to compensate for the air leak' and the ECU will be fueling accordingly.

I recently picked up a V6 and was having trouble with emissions for MOT. Turned out the Lambda was not a Bosch*. Amazing that someone (and the car) had put up with that for 6 years since it was fitted.

(Thanks to Gazza82 for the suggestion earlier this week)

 

[Leaky 156]

Passed MOT, btw

 

[alfizta]

MOT no sweat here too 2 months ago. So, lambda fault dropped. It's original Bosch btw. I just wanted to know if the ECU can "disguise" an air leak in the exhaust (before the lambda sensor) by adapting the TRA parameter or others?...

 

[Rockhopper]

The ECU can make adjustments to compensate for certain fault conditions and within certain limits. The car may run but probably not quite right. This is why cars often run better after an ECU reset as they go back to a default "safe" map but slowly return to how they were becasue the original fault is still there.

 

[alfizta]

Yes, I'm sure that it can do that for an intake manifold leak. But for an exhaust manifold, is it possible?

 

[rarebear]

depends on where the leak in the exhaust is, in front of the sensor or aft ....

 

[Rockhopper]

Exactly.

 

[alfizta]

in front, between the engine and the lambda sensor.

 

[alfizta]

and another thing...
could I detect an air leak by comparing "air quantity" and "desired air quantity" in Multiecuscan?

 

[Rockhopper]

Easiest way is to get your head in there and listen for it - also hold a bit of tissue paper close to all the joints, it'll soon show any gasses escaping.

 

[alfizta]

Ok!

EDIT: jumping idle and p1172 fixed. new MAF, but also fixed some vacuum leaks.