Hi,

I have a Jaguar x308 3.2 1999 aj27 with a 4.0 aj27 vvt delete engine. I have one problem, high fuel trims and awful emissions.

I get like 16mpg, 14L/100km

My fuel trims bank 1&2
STFT +25
LTFT +19.5
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My emissions:
CO 9.1 (0.3)
CO 2500rpm 7.1 (0.3)
HC 375 (200)
Lambda 0.8 ( 0.97-1.03)

This did not come after the engine swap it was like this with the old 3.2 engine and it was even worse then, why It got changed was due to a failed thermostat housing failure and cook the engine.

Anyway, I get no codes, I have the single canister evap system. And 4 o2 sensors.

I changed the maf, both upstream o2 sensors, ect and air filter, still the same. Injectors did leak air but it's fixed now.

The funny thing is when the injectors leaked air it almost passed the emissions test.

With air leak I got:
​​​​​CO 0.0 (0.3)
CO 2500rpm 1.5 (0.3)
HC 6 (200)
Lambda 0.95 (0.97-1.03)

I did a hard reset still no change, I looked at my cats, they look like new.

​​​​​No leak from hoses.

Engine runs smooth.

I found one weird thing that I will try.

My purge valve, I can blow by air from one side (the side where the hose goes to canister to part breath hose but not the other way. So maybe a evap leak?

Please help!

 

I can’t imagine a 3.2L ECM is doing any favors for a 4.0L engine. Are you still running the 3.2L fuel injectors and FPR? Just for the record, I don’t know if there’s any difference between the 3.2 vs 4.0 injectors/FPR.

Did you replace every intake manifold gasket when you replaced the engine?

It might be wise to get a smoke machine for this issue.

 

Well, ask sean B, he did this conversion, the engines has the same injectors. I double checked my gaskets and they did not leak.

I know it's gonna be hard to understad this conversion but anyway, I have no smoke machine but I will try to get one.

 

A prime suspect is the corrugated looking plastic hose thar runs from the left valve cover, under the intake manifold, connects under the throttle body and then connects to a device at the firewall. They can rub a bit on something and wear a tiny hole or form a crack that will cause these a vacuum leak. I know this because I too changed a lot of parts/ gaskets trying to solve the problem on one of my cars to no avail. I ended up disconnecting the hose end from the valve cover and removed the throttle body. Then blew some low PSI air into the hose and could hear the tiny hissing from under the manifold. )You will need someone to hold their finger on the throttle body connection though!) On careful inspection I found that the hose had a worn spot which caused the leak.
That plastic hose is a weak point on these cars. If you cannot repair it or find a replacement, you may carefully cut it from the plastic ends and install a rubber hose from the auto store.
Also, check the oil cap gasket. A hard worn one was the cause on another of my cars. New cap finally got the trim numbers in line.
Just my experience; your mileage may vary....

 

I found the issue, it was my downstream o2 sensors that was fixed lean at 0volts making the fuel trims go crazy. Now my emissions are great.

Tailpipe emissions results:

CO idle: 0.00 (0.5)
CO 2500rpm: 0 (0.3)

​​​​​​HC 45 (200)

​​​​​Lambda 1.01 (1.03.)

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