[Andy K]

Yeah I’m looking at the ST when reved @1600 and its bad. -19 I think

At idle and higher RPMs its a more acceptable value. (single figures)

And yes the LT is bad too.

Note to self, I had to change the fuel pumps a few days ago.

[Andy K]

So as I partly suspected, the 8 g/s air reading was the last valid reading, and not a reading with the engine off. Replacing the AMM with a used item hasn’t changed the live value readings.

The origional AMM reads about 0.5 – 0.7 g/s in free air (from memory)

I’m running with the EGR plug disconnect at the moment. The long term fuel trim values seam great at the moment. (less than 2%). I discovered similar 2 years ago when I blanked the EGR (though the effects didn’t last into winter, however the EGR to inlet connection was loose at that time, I since discovered)

Can anyone give me any clues as to why not using the EGR makes the trims good?

I’ve had the EGR off previously and it seams sealed when closed. This is proved as I only disconected the electric plug this time.

[Andy K]

Regarding the oxygen sensors, I found out from the manual, the location of the sensors is deliberate.

upsteam has constant voltage output, with linar current/AFR from 12:1 to 18:1.
The linear characteristic allows very accurate feedback control.

HO2 is fitted downsteam and has a sharp response at stoichmmetric so provides a reference for the upsteam sensor .

The stoichmmetric output of 450mV is maintained more accuratly than before by the upsteam linear sensors

[Andy K]

Well sadly that hasn’t fixed it.

I notice today that the AMM reads 8 g/s with the engine off!
And 6 g/s with it idling.

Are they usually this inaccurate at idle? or is it suspect ?

Thanks

[Andy K]

Had the throttle body off today and the EGR

The EGR bolts weren’t tight so could be letting in unmetered air.
There was oil in the TB and this had been leaking out the mating face for the EGR.

Too early to say if it’s improved it.
Oxygen outputs are tracking each other at present

[Andy K]

Ok thanks.

I only got a P0400 when I blanked the EGR (insufficient flow, so it was correct)

I will take a look at the SC bypass when checking the EGR (as its not far from the EGR)

[Andy K]

What u thinking as I may not be able to check EGR for a while ?

[Andy K]

Thanks. Yeah I think I need to investigate the EGR.

Thanks for your help

Yes it’s supercharged.

[Andy K]

You mean at the tank end?

The UK cars don’t have one there. It’s open after the charcoal canister.

If you look in my other post there is a diagram layout linked.

[Andy K]

Hi. Thanks for your reply.
I have already checked the purge valve throughly and it’s fine.

[Andy K]

After nearly 1 hour still registering 38 psi.

No fuel in regulator vacuum line

[Andy K]

The dealer changed the regulator when the car was 3 years old in an attempt to fix the problem. I have the original.

Just a pain to get to the items.

But I’ll have a look next weekend thanks.

[Andy K]

So just a small update. I can’t perform the full test as my setup started leaking!

What I did find out, (without the engine running).

With the pump running I get 45psi. As soon as the pump is stopped I get 40psi.
This is consistent and instantaneous. and before I had a leak.

Will update when I get a new hose.

[Andy K]

Will check to see if the fuel pressure holds. Thanks.

Codes here. Rich both banks.

Jaguar xj 308 P0172 P0175 RIch

[Andy K]

Maybe I need to get a better ISO9141 diagnostic tool, to look at the upstream sensors. (rather than downstream)

actually Mine says,
oxygen sensor 5 wide range equivalence 14.65
oxygen sensor 1 wide range equivalence 14.53

What the hell is oxygen sensor 5 !!!

[Author]

Posts