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My short and long term trims look really high. Car keeps setting lean codes for both banks. Im looking for vac leaks but havnt found any.
Replaced MAF sensor.
Does your reader provide O2 Sensor codes? How many miles are on your car? It is an 2004 correct? What codes have you had to lead you to replace the MAF?
Just to exclude the catalysts (or at least put them to the end of the priority list), damaged catalysts wouldn't cause the observed effect. If the coating is damaged and conversion is lacking that is bad for the environment, but wouldn't concern the lambda probes in front of either catalyst. They just look for oxygen in the raw emission coming out of the engine.#
As you have similar readings on both banks it is unlikely that the problem is behind the engine (i.e. on the exhaust side) because a leak in the exhaust would only affect the reading of this one bank. The exhaust pipes only connect after the catalysts. Not impossible but extremely unlikely to have leaks in both exhaust sides that are "calibrated" in size so that they have the same effect on both banks' readings.
So you need to look at everything that both banks share.
- intake systems after MAF
- throttle module
- all hoses connecting into the intake system
- PCV systems (both part and full load)
- vacuum line to the brake master cylinder
- sealing between intake manifold and cylinder head
- oil dipstick sealing
- oil refiller cap sealing
- evap system
Probably some more when thinking and searching longer, but that's the list I go / went through on mine currently.
Oh, and when all that is to no avail, there is still the theoretical possibility that the fuel injection system is not delivering enough fuel through the injectors. Maybe fuel pressure is too low, so that the mapped injection timings are resulting in too low fuel quantities? Again, it would have to be a problem that affects both banks the same, so no individual injector but something systematic.
I'm not sure the PCM can actually enrich the mixture >50% combined. Do you have another scan tool you can try? My intuition is that there's a decimal point missing from those readings.
If they were 14.6, 14.8, 12.9, etc, that would make sense. When the combined LT and ST trims exceed 20% or 25% enrichment (can't recall the code setting criteria offhand) the PCM sets a lean code.
I have read similar figures for my XJR using the carsoft i930
However when I chose another way to read the data on the scanner, I think OBD11 diagnose and 'LIve Data Stream' the figures for all the trims were well within the expected limits
I'll check tonight how I read the fuel trims that seemed normal.
Please don't keep us guessing - tell us the year, model and engine of your Jaguar. It's best to add this info to your signature line so it shows up in all of your posts. To do so, use your User Control Panel (User CP link above left), then find Edit Signature in the left column of your Control Panel, add your car info and save your signature.
if i pull the PCV pipe off whilst the car is running my icarsoft I930 sets a MIL at 20% and maxes out at 25% .
pcv pipe off/removed is a massive vacuum leak .
yours is off the scale as if your heads are removed .
i think your I930 needs a software update .
it should look like this - and even this has decimal point's -
Sorry, didn’t log in yesterday. Our Jag is a 2004 XJ8 Vanden Plas.
I’ll see if I can change scanner settings tonight to get different numbers and add O2 sensors. I just got it and am trying to figure it out.
thanks for the tips. I took the cover off top of engine the other day and it does look like rodents have been chewing on some vacuum lines. I’ll replace those, and have two VVT seals ordered since there is some oil on the valve covers around both.
Replacing the two VVT seals on the valve covers dropped the short terms to hover around zero now on the live data scan. LT’d are slowly dropping, but still around 10%.
After clearing codes and driving 100+ miles over a 4 day period the CEL never came back on.
The car passed inspection! Woo Hoooo!
I’m still going to replace the rodent chewed vac lines, and I think I hear a leak on the passenger side intake manifold so will probably go ahead and replace those gaskets.
Thanks for the suggestions and ideas.
I had exactly the same, after the leak was fixed the LT didn't want to drop below 10 for several hundred kilometres.
After a hard reset and the corresponding revival procedure (described very well here in the forum) they finally started at zero again and didn't go back up. I would recommend that to you too.
There seems to be some glitch in the adaptation programming that keeps the LT stuck around 10 on their way down. And ST will then compensate with -10 ... it needs help to get over that.
I had lean codes for bank 1 which ended up being caused by an intake manifold leak and a valve cover leak. Check the connector piece on your valve cover (where the vacuum tube from the air intake connects). See if it is broken (mine was).
Fuel trim numbers look wonky?
