I have been noticing a slight hesitation on the highway, sometimes around 70-80mph.
cant notice if I give it a lot of gas, but seems to be more when I am accelerating at a steady pace at higher speeds.
the car runs fine otherwise and still pulls strongly, no complaints. I am wondering if there is a simple way to check injectors and or fuel pump.
i took some readings while parked at idle/1500/2500 Rpm for ltft and stft, but I’m not sure they indicate an issue.

they are as follows:
@ idle 760rpm stft b1 -2.3/ ltft b1 17.0/ stft b2 -1/ ltft b2 18.0, fuel pressure 515, map 12inHg

@ 1500 rpm stft b1 2.0/ ltft b1 11/ stft b2 3.0/ ltft b2 11, fuel pressure 800

@ 2500 rpm stft b1 -12/ ltft b1 9/ stft b2 -13/ ltft b2 11, fuel pressure 960

does anyone see a glaring issue with these duel trim numbers? Or do i need data while actually driving?

 

Parked is best.

Those LTFTs are big and as they drop with revs you may have an air leak. As they don't drop near zero you may well have another problem (as well or perhaps instead).

The hesitation may be misfires especially coil(s) failing.

 

ive attached some live data to see if anything is obvious. I have checked several times for leaked but found none. I did replace the pcv recently and that helped some. I will receheck for leaks, I am assuming they would need to be
Between the maf and throttle body?

 

Fuel trims

 

Trims

 

I don't know if this is your issue, but if you're trying to attach a video to the post, you'll need to wait a while until it's actually uploaded, and I think the only way to really know is when the attachment screen shows a filesize next to the file you're trying to upload.

Alternatively, upload the video to youtube and paste the link here - probably more reliable.

 

Thanks Dave Tibbs,
Yes, i feel foolish but I couldn't get the file to upload.
hopefully this will work.

https://drive.google.com/file/d/186I...ew?usp=sharing

 

My vacuum leak on my 5L 2010 XJ was due to a crack in my intake, right where the intake goes over the throttle body. When I removed the hose clamp it was clearly broken. I had another one caused by a crack in the vacuum tubing that drives the supercharger bypass valve (tubing connecting the intake to the throttle body through the actuator). Not sure if you have this last one on your model (on the XJs there were vacuum controlled and electrically controlled sc bypass actuators).

Not an expert, but I believe running lean typically suggests a vacuum leak is occurring anywhere after the MAFs allowing unmetered air into the engine (though it technically could also be poor fuel pressure...etc, but this is rarer). So I’m not sure it has to be a leak before the throttle body.

Best of luck.

 

Thanks Nedoerr,
what were your symptoms from a small crack in intake? Did you have a code?
i have an aluminum Mina intake and it looks fine, but I think I will remove and reinstall just in case there’s something small with the couplers I am missing.

 

My car almost never throws codes. I think you need to be greater than 25% plus or minus LTFT to throw a code (maybe 30%). I found my leaks investigating a rough idle. In response I had the leaks and a bunch of other stuff repaired. After all that now my car decides to run rich. The Jag master technician says it’s high fuel pressure now (either pumps, pump timing, or fuel pressure sensor). So the rabbit hole continues.

Wish I had a more linear repair story to share. Though I have been watching my fuel trims pretty closely and they have tended to reflect the leaks and fuel pressure issues fairly well.

 

Wouldn't being lean in only one bank suggest a leak on only that side of the engine? Specifically the intake manifold to blower gasket or possibly a cracked intake manifold? If the leak was before the throttle body (but after the MAFs) both banks would show lean (positive fuel trims).

Edit: Oops read OP's first post wrong. I had this same issue on mine, ended up being a damaged intake right at the throttle body as Nedoerr suggested. When I removed it, the part the clamp secures completely fell apart.

 

So has the solution to this problem been found?! I have a 2012 XJ w 5.0 SC and there’s this hesitation that kills the fun of driving. So far, I have replaced the fuel filter, transmission fluid and filter, and finally a cracked intake hose. All to no use. The car still hesitates. Would appreciate if the solution was found and shared like you can’t imagine!

 

For mine, I did find my pcv valve was almost completely torn. After replacing the diaphragm fuel trims did improve a bit and I did not notice the same flat spot in my power curve...
that was a while ago and all is pretty well still...

 

Did the PCV leak cause a check engine light?
.
.
.

 

in my case, yes it did cause a cel, but I have heard from others who had same tearing issue but didn’t get a cel