That would make it free flowing. Blocked cats on the XK’s typically make them misfire under load.

 

I get everyone is entitled to their own opinion, but yours is wrong

 

Yep everyone is entitled to their own opinion. And I agree with Rivguy, F-Types sound like they need a tune up. Never understood the fascination with the pops and crackles, must be a younger crowd deal. Sorry "StormtrooperFtype" but it is impossible for an opinion to be wrong. Except for of course your opinion of opinions.

 

I found that on most cars, blocked cats just severely limit power output but do not cause any misfire.

 

Lol! Imagine how polarizing this would be if we couldn't turn them on and off!

Quick pop and crackle story. I live down the street from a country club golf course. I perfectly timed a downshift to the apogee of a poor fellows backswing. POP! He jumped a foot into the air and sliced into the rough. Turnabout is fair play, so he quickly dropped another ball and took a shot at the F-Type. It was close but the ball hit a tree near the side of the road with a group of deer enjoying the shade underneath, They scattered every which way. It doesn't matter how terrible a day I'm having, whenever I think of this I laugh out loud. Thank you, F-type.

 

Is there possibly a fuel flow issue? Perhaps a dirty fuel filter, fuel pump going bad, etc?

 

Could be! I just flashed back to stock about 5 minutes ago, and have a long drive ahead of me - if all my issues go away... that will be interesting.

Could be fueling.

 

Not the tune. Same issue as stock.

99% sure it’s a cat - but will have them look at plugs too.

 

You might be right but I was just going by what I see people who know a lot more about cars than me post on the forum e.g.

https://www.jaguarforums.com/forum/x...8/#post1864222

 

absolutely convinced it’s a cat now.

**** me our catalysts are fragile! I ran an S4 misfiring and a a4 with dead coils and never had a catalyst issue. Wild.

 

I wish I could edit the title because it’s definitely not the tune. Sorry @Stuart@VelocityAP - what’s your thoughts? Catalyst damage from injector failure? It’s worse the warmer the car gets.

 

Like I said a "younger crowd" deal.

 

A guy on the XJ forum measured his cat temps with one of those laser thermometers at the front and back of each cat. He diagnosed his blocked cat by hotter temps at the front of the cat than at the back (I think it was ~ >100 degrees Fahrenheit difference, IIRC). It’s a cheap diagnostic test if it works for you.

 

From everything you’ve mentioned, specially when you punch it to downshift and trigger a misfire..I would definitely inspect the catalysts.

If a catalyst is blocked(commonly melted stock ceramic core), this would increase backpressure precat more than a 2psi average, resulting in the exhaust fumes not being able to exit the chamber effectively. If the intake/drawn air does not have enough volume to fill in the combustion chamber(due to excessive exhaust fumes not expelled, volume occupied), this would force a misfire due to lack of oxygen..the function of power from combustion would drop and the ecu would instantly pick up on the lack of power when X cylinder was requested to ignite.

To diagnose, have different methods you could use;

1. can drop the downpipes and visually inspect. (Best)
2. can remove upstream sensor and check pressure during suspected rpm range.(Good indication but would still invoke pin pointing concern, aka drop downpipes)
3. can hook up a vacuum gauge to the intercooler pressure line. Depending on the parts you have will dictate the maximum charged pressure you should have as spec/reading. If you notice the pressure spikes more than 3psi of expected, it’s a good indication a restriction is inside the exhaust. *Intake charged pressure will increase as Exhaust restriction increases*(good, but would need to drop pipes to inspect if datalog proves issue present)

 

Time to move on to VelocityAP downpipes if yours are melted!

 

cant, Cali!

 

 

I know buddy, besides, that $1,400 is better spent in Montreal at soubois or something ;-)

 

LOL, not for me personally but whatever floats your boat!

 

Okay maybe not Soubois, but Nouveau Palais late night stoned works for me too.