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today I had gone out to do some errands and as I was driving I noticed when I gave enough gas, such as speeding up to get around some one, it would jerk once it started making boost around 2500-3500 rpms.
But when I gave it WOT it ran through the gears seemingly fine maybe a little down on power.
I recently had this supercharger rebuilt, fitted with smaller pulley and ported by Powerhouse Uk along with the throttle elbow.
The engine itself has also undergone a full rebuild, new vacuum hoses, new coolant hoses, resurfaced heads, head studs, etc.
So back to the supercharger, the first day I had it fitted it ran like a dream not a single bad sound.
I put about 100 miles on it and I start to hear almost like a turbo flutter when I would let off the throttle. Could this be compressor surge?
At the end of the video it’s the most audible, right after I let off the gas you can hear its kinda high pitched.
This lasted for about a month and only today has it actually caused the car to react in any way.
I do know that there is a rip in my throttle body gasket(green gasket) aswell as the 2 circle gaskets that connect the Charge Air Coolers to the Top Plate were noticeably old and torn, and this may be causing the jerking.
Side question and I feel dumb even asking it, but after the engine rebuild and I put new oil in and everywhere say 6.9quarts of oil so I bought 8 to be safe and only threw in 7 and it’s up to my thumb in the picture. This is after I the dropped oil pan and heads were off.
Should it be between the two dots? And am I loosing power due to excessive oil?
Your dipstick holes are top is max bottom is minimum, you look about a 1/3 of a quart low. I dunno, but did you check the fluid in the SC...and did they put in an OEM spring loaded coupler? It says coupler on their site, but it doesn't say OEM.
As for your duct seals, oh heck yeah they can be an issue if they are dry rotted or just old. You are pulling more air now and it's pulling on your ducts harder, those should be new. Have your clamp plates been replaced with upgrades ones with a lip to hold the duct seals in place. I'll include the TSB PDF....
Last edited by Highhorse; Nov 19, 2025 at 07:43 PM.
Your dipstick holes are top is max bottom is minimum, you look about a 1/3 of a quart low. I dunno, but did you check the fluid in the SC...and did they put in an OEM spring loaded coupler? It says coupler on their site, but it doesn't say OEM.
As for your duct seals, oh heck yeah they can be an issue if they are dry rotted or just old. You are pulling more air now and it's pulling on your ducts harder, those should be new. Have your clamp plates been replaced with upgrades ones with a lip to hold the duct seals in place. I'll include the TSB PDF....
When I had it off it held the gaskets on there, so I think it is the new one. When I was searching online the only gaskets I found said they were for 2000-03 x308s. Can I still use those? And are there any places that are cheaper than $150 a piece?
I’m going to go ahead and take the belt off the supercharger and see if the car still jerks and makes the flutter noise.
As for the oil, it is above the top dot probably a good inch.
Can you put your MY and such in your signature, it would help out to know which MY you have. Check your owners manual about that dipstick, I don't believe it should above the top hole.
Good idea to remove the belt and check, ...also to check your SC fluid, on the bottom right there is a recessed plug with an alen wrench head. To remove the plug to check the fluid use the method Don B shows in Post #36... https://www.jaguarforums.com/forum/x...y-85828/page2/
I can only improve on Don's by saying to put a light colored towel under that plug area so if you do drop it, it only goes as far as the towel and easier to see to pick up with a magnetic tip. Check it with the inter-cooler cold and car on a level surface,
**...if fluid comes out as your removing the plug (pay attention it will be very clear), just reverse the wrench and tighten it back up, your fluid is fine. That being....When refilling during a replenishment you simply put in fluid until it trickles out and your done.
**If you don't have fluid coming out check the end of the plug to see if its had fluid on the one edge which would be the bottom when tight and your good.
**If not you need to check the amount buy perhaps taking a Q-tip and just barely put it in as level as possible, remove it and it should have absorbed fluid if its at the correct level.
**If you still don't get any fluid, then you most likely need to add some.
Have you contacted your local Jag dealer on pricing or was that $150 it...what condition are yours in? I know I said they should be new, but if they are in real good condition, I'd let it go.
So I did some scrounging and it appears the XKR duct seals will work up until 2009...a couple numbers came up...AJ81446 and AJ86925...verify before purchase. They were running about $90-112 ea.
Last edited by Highhorse; Nov 20, 2025 at 07:41 PM.
If you have an OBD reader, have a look at 'live data' and STFT/LTFT (short and long term fuel trims) if they are negative you have a boost leak, and you have already suggested the duct seals, if they're damaged that's the likely cause of rough running and an unmetered air leak, hence the ECU tipping fuel in to compensate - I've just fixed one. Located the air leak by spraying easy start all along the induction path, located at the seals.
Pull a half litre out of the engine and get the level between the dots.
Oil level wise, there was a TSB to increase the amount of oil in the engine & a new dipstick to suit. Worth a quick check in case yours has the correct level but on an old dipstick
Can you put your MY and such in your signature, it would help out to know which MY you have. Check your owners manual about that dipstick, I don't believe it should above the top hole. 1998 XJR I have it under vehicles on my profile, is there somewhere else I should put it?
Good idea to remove the belt and check, ...also to check your SC fluid, on the bottom right there is a recessed plug with an alen wrench head. To remove the plug to check the fluid use the method Don B shows in Post #36... https://www.jaguarforums.com/forum/x...y-85828/page2/
I can only improve on Don's by saying to put a light colored towel under that plug area so if you do drop it, it only goes as far as the towel and easier to see to pick up with a magnetic tip. Check it with the inter-cooler cold and car on a level surface,
**...if fluid comes out as your removing the plug (pay attention it will be very clear), just reverse the wrench and tighten it back up, your fluid is fine. That being....When refilling during a replenishment you simply put in fluid until it trickles out and your done.
**If you don't have fluid coming out check the end of the plug to see if its had fluid on the one edge which would be the bottom when tight and your good.
**If not you need to check the amount buy perhaps taking a Q-tip and just barely put it in as level as possible, remove it and it should have absorbed fluid if its at the correct level.
**If you still don't get any fluid, then you most likely need to add some.
Have you contacted your local Jag dealer on pricing or was that $150 it...what condition are yours in? I know I said they should be new, but if they are in real good condition, I'd let it go.
So I did some scrounging and it appears the XKR duct seals will work up until 2009...a couple numbers came up...AJ81446 and AJ86925...verify before purchase. They were running about $90-112 ea.
Thank you for tips n link on how to go about it, it’s my first supercharger n dont want to ruin it lol.
I have not talked to my local dealer, I’ll give them a call and thank you for finding cheaper seals.
Originally Posted by Sean B
If you have an OBD reader, have a look at 'live data' and STFT/LTFT (short and long term fuel trims) if they are negative you have a boost leak, and you have already suggested the duct seals, if they're damaged that's the likely cause of rough running and an unmetered air leak, hence the ECU tipping fuel in to compensate - I've just fixed one. Located the air leak by spraying easy start all along the induction path, located at the seals.
Pull a half litre out of the engine and get the level between the dots.
I’ll def try out the easy start and see if I can confirm it’s the gaskets before taking it all apart, thank you for the idea.
As for the oil I’m going to check if I have the correct dipstick as Hooli mentioned.
Originally Posted by Hooli
Oil level wise, there was a TSB to increase the amount of oil in the engine & a new dipstick to suit. Worth a quick check in case yours has the correct level but on an old dipstick
Thank you for tips n link on how to go about it, it’s my first supercharger n dont want to ruin it lol.
I have not talked to my local dealer, I’ll give them a call and thank you for finding cheaper seals.
I’ll def try out the easy start and see if I can confirm it’s the gaskets before taking it all apart, thank you for the idea.
As for the oil I’m going to check if I have the correct dipstick as Hooli mentioned.
Thank you, I never knew they had done this.
I was also able to get a better video of the noise please listen. It kinda sounds like metal now.
l
You have a big air leak. Locate and fix before trying to drive the car.
It's a bit hard to tell from diagnosing over video... The blowers do make a bit of warbly noise at idle in general, but if it sounds very rumbly, especially from the back of the blower, it could be SC rear needle bearings? If you're starting to go down that rabbit hole, I'd suggest buying a mechanics stethoscope for under 10 bucks, poke things and listen. That'll help isolate the source of your noise.
It's a bit hard to tell from diagnosing over video... The blowers do make a bit of warbly noise at idle in general, but if it sounds very rumbly, especially from the back of the blower, it could be SC rear needle bearings? If you're starting to go down that rabbit hole, I'd suggest buying a mechanics stethoscope for under 10 bucks, poke things and listen. That'll help isolate the source of your noise.
I replaced my throttle body gasket and it definitely helped with the more severe jerking but there is definitely hesitation in it when I hit the gas enough to get boost. SUPERCHARGER BELT ON.
With the supercharger belt off, the car doesn’t seem to jerk as much, if at all but I haven’t gave it much gas since I’ve taken it off.
Is that clunking normal? It also happened moving it up and down just not as loud.
And with a stethoscope, it sounded like it was coming from the snout the loudest.
That clunk falls back onto what I was asking if they used an OEM spring coupler and if your fluid level was correct in post #2. But that does seem like a bit of excessive play, I'd be contacting your builder Powerhouse. It's been awhile since I've had mine off, I know there is a bit of play back and forth with the rotors. I'm quite sure there's not supposed to be any snout play up and down, which could seemingly indicate a snout bearing issue. Let some others chime in to see there opinion. You can try contacting Powerhouse because England doesn't celebrate Thanksgiving.
I replaced my throttle body gasket and it definitely helped with the more severe jerking but there is definitely hesitation in it when I hit the gas enough to get boost. SUPERCHARGER BELT ON.
With the supercharger belt off, the car doesn’t seem to jerk as much, if at all but I haven’t gave it much gas since I’ve taken it off.
I got the fuel trims here. SUPERCHARGER BELT OFF 0-45 No throttle after hitting 45 Idle Supercharger
Is that clunking normal? It also happened moving it up and down just not as loud.
And with a stethoscope, it sounded like it was coming from the snout the loudest.
Your LTFT are unbalanced and one goes too rich (bank B) Could it be a leaking injector?
That clunk falls back onto what I was asking if they used an OEM spring coupler and if your fluid level was correct in post #2. But that does seem like a bit of excessive play, I'd be contacting your builder Powerhouse. It's been awhile since I've had mine off, I know there is a bit of play back and forth with the rotors. I'm quite sure there's not supposed to be any snout play up and down, which could seemingly indicate a snout bearing issue. Let some others chime in to see there opinion. You can try contacting Powerhouse because England doesn't celebrate Thanksgiving.
Powerhouse are open Saturdays too, at least part of the day.
I need to speak to them tomorrow, if I remember I'll ask about this. I suspect it's snout bearings as suggested though.
That clunk falls back onto what I was asking if they used an OEM spring coupler and if your fluid level was correct in post #2. But that does seem like a bit of excessive play, I'd be contacting your builder Powerhouse. It's been awhile since I've had mine off, I know there is a bit of play back and forth with the rotors. I'm quite sure there's not supposed to be any snout play up and down, which could seemingly indicate a snout bearing issue. Let some others chime in to see there opinion. You can try contacting Powerhouse because England doesn't celebrate Thanksgiving.
Ill definitely get in touch with Powerhouse and see if I can’t get some more answer.
Originally Posted by BringBackFord
Your LTFT are unbalanced and one goes too rich (bank B) Could it be a leaking injector?
How would I check if it’s a leaky injector?
And if Bank B is passenger side, could that be a 02 sensor causing it run rich? As I may have an exhaust leak on the passenger side, I can hear what sounds to be the exhaust rumble only when I’m parked or on the brakes at a stop. The noise goes away once I let off the brakes.
Stop messing around and address what I've told you - IT'S NOT THE SUPERCHARGER.
Hi Sean, yes I have sprayed easy start all over that area and nothing happened. This was without the supercharger running, so i don’t know if it was able to pull enough air from the duct seals to do anything.
Hi Sean, yes I have sprayed easy start all over that area and nothing happened. This was without the supercharger running, so i don’t know if it was able to pull enough air from the duct seals to do anything.
Hi Sean, I put the belt back and tried it again and still nothing from any intake gasket or vacuum line.
it still starts to hesitate when I put more than 5 pounds of boost or so.
I also noticed on my boost gauge the vacuum would go up and down a little but when at idle
Jerking around 3k rpms
