XJ XJ8 / XJR ( X308 ) 1997 - 2003

stuttering on acceleration / full throttle

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Old 01-26-2018, 07:22 PM
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Default stuttering on acceleration / full throttle

Hi Gents

Itīs about my XJR 2001.

I have replaced the lower and upper pully (bigger/smaller) for more power and switched to an extra big supercharger cooler. During that, I realised that the supercharger water system is the same as that from the engine.
Is that silly ?!, so the supercharger water system will allways have the same temperature as the engine water system so power is allways degraded because of that.

I also have changed the catalytic converter from original to 200 cells, I welded that by my own and one side will not line up with the connector going to the rear. There is a very small slit between the gasket you canīt hear it but I can smell it.

Sorry for the big intro... :-) now the problem: When I accelerate at full throttle the engine stutters.

First I thought it might have something to do with the exhaust issue, but now I think it has somehting to do with fuel pump. Is it possible, that after the pully change it is also necesary to upgrade to a stronger fuel pump ?

As far as I know the XJR has 2 fuel pumps. Which one should I change ?

So...what do you guys think ?

Thanks
Frank
 

Last edited by neo4star; 01-26-2018 at 07:34 PM.
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Old 01-26-2018, 08:27 PM
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The # 2 fuel pump relay is next to the # 1 and can be hot wired by putting a jumper ( with a knife connector so no arc damage to the sockets ) in the 2 larger of the 4 relay wire sockets . Remove the # 1 relay and listen for the # 2 pump as the power source it hot at all times and there is a fuse after the relay before the connector .

There is a command on control out of the ECU we can look at after you do this to see if it resolves your spot of stumble under the bonnet .

You may have 2 under performing relays that can be swapped out from elsewhere as a least intrusive try .

Yes on Highhorse's recommendation below on fuel filter change .
 
Attached Thumbnails stuttering on acceleration / full throttle-x308-fuel-fuses-untitled.png   stuttering on acceleration / full throttle-x308-fuel-pumps-ntitled.png  

Last edited by Lady Penelope; 01-26-2018 at 08:41 PM.
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Old 01-26-2018, 08:29 PM
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The only thing the under drive pulley does is rotate the snout shaft faster so the power comes in quicker. The thing is you reach your SC's top end quicker and you have run out.
For your stuttering, I believe you may have a O2 going south, it just hasn't registered a hard code yet. I say this from your CAT replacement. Its also possible you may only have to run it a bit to allow the ECU to measure the new CAT.
If it was a failed pump, you should of gotten a code from that. Check your fuel pressure on the rail. When's the last time you changed your fuel filter? Are you getting any Restricted Performance?
 
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Old 01-26-2018, 09:33 PM
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The SC intercoolers and engine cooling share water, but the flow path doesn't tend to overlap except for overflow and bleeding. Take a steady drive on a cool day, get your engine up to full temp, then stop somewhere, pop the hood, and feel the intercooler hoses. They will be cool to the touch, where the engine radiator hoses will probably be too hot to hold onto for too long.
 
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Old 01-26-2018, 10:00 PM
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With Nilanium's recommendation the 3rd water pump ( same as cabin heat but for the intercooler ) should be running under certain conditions ( key run ? ) through a relay . You can feel for the pump running . As to it's location might find it in this link :

https://www.jaguarforums.com/forum/x...ckwards-98938/

In post # 6
 

Last edited by Lady Penelope; 01-26-2018 at 10:36 PM.
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Old 01-26-2018, 11:35 PM
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In installing the intercooler was the Inlet Air Temp sensor hooked up . I don't have the SC but by design it should be after the intercooler so that puts it's location in a bad place . Without the temp input the ECU maps would shift to a default which may be a shortcoming you are seeing . I could be wrong .

You can test for the sensor hookup at the ECU connector without removing the intercooler if It's located under there , just remove the battery connector first .

IAT 2 : EM81 - 23 ( Orange wire ) to EM83 - 13 ( Black Green wire ) for 2001 All of World SC engine marked in the pic below :
 
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Last edited by Lady Penelope; 01-27-2018 at 12:01 AM.
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Old 01-27-2018, 01:07 AM
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As above, 2 water circuits, sharing a tank.

Stutter could be misfires.
 
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Old 01-27-2018, 04:26 AM
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I did the upper and lower pulley swap on a customers XJR-100 but they also had the ecu sent out for a reflash. I believe we sent it out to paramount. Did you have yours reflashed?? I'd look more into that as I believe there's a reason why. Timing possibly?? If you end up changing one pump, change them both as you'll need all the extra fuel you can get.
 
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Old 01-31-2018, 10:59 PM
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Question Similar Problem

Hi - I have just installed a Powerhouse lower pulley on my 2000 XJR. On its first decent run the performance suddenly dropped off, restricted performance mode engaged and the engine was running a little rough. After stopping for a time restricted performance mode went off but the car still felt a little rough. A while later during a bit of hard acceleration RP came on again and the engine was noticeably rougher running again. Computer shows an intermittent knock sensor issue. Mechanic thought it may be a faulty sensor because of the way the fault showed up and it has been an intermittent fault prior to pulley change. He is also wondering whether it is a fuel supply problem - I would have thought that if a fuel problem of this nature the engine would probably run OK under normal driving and only kick in under load?? Any comments/suggestions appreciated.
 
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Old 02-01-2018, 10:53 AM
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You hit it, its almost assuredly the knock sensor Gobbers. Intermittent code, try to accelerate hard or go to fast and she chugs hard like a stall until you let off the gas. You probably have a P0332 or P0333 stored to. I am dealing with that exact same scenario now. I have the sensor, I just have to get the time to pop off the SC and replace it. I'll probably do both since I really don't wish to do this job again anytime soon. FYI, you can get a knock sensor from Autozone for $69 (Duralast), which is the best price I could find anywhere.
 
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Old 02-01-2018, 11:25 AM
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The # 2 fuel pump doesn't turn on until certain high demand conditions or from # 1 pump failure . But you can trick both on at all times or just # 1 or # 2 for troubleshooting and you would still need to verify the # 1 and # 2 main power to the pump fuses for this test .

You could have a fuel pressure regulator failing by bypassing to a low fuel rail pressure condition and underfueling .

Injector cleaning by a least intrusive try of a tank additive ?
 

Last edited by Lady Penelope; 02-01-2018 at 11:48 AM.
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Old 02-01-2018, 01:50 PM
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Thanks, Highhorse - that is great info. Cheers
 
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Old 02-01-2018, 01:51 PM
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Thanks, Lady Penelope. Another good option to consider. Will have a look at this too.
 
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Old 02-01-2018, 04:10 PM
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Hi Highhorse - I have spoken with my mechanic and to save time and money I am going to source the parts. From your reply I take it there are two knock sensors? Also given the supercharger needs to come off what gaskets/seals are needed? I also noted some comments elsewhere about some heater hoses that it would pay to replace while s/c is off as they can become brittle over time - are you doing those on your car? Any info appreciated. Cheers
 
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Old 02-01-2018, 08:40 PM
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I did my hoses when I did my tensioners a couple years ago. I'm trying to recall about any gaskets for the SC for which I don't believe there are to do this. I believe all that needs to be undone has reusable gaskets. I'm sure someone will correspond that. If I am correct, I should only have to remove the belt, unbolt the cooling cap, the intercooler plate, unbolt the SC mounts, undo the TB mounts, take off the thermostat crossover (may be the only gasket to replace?) and bring the front of the SC high enough to access the sensor for removal. Its scenarios like this is why I document these and provide the info for the How-To section where its not already covered. Its also why I am probably going to do both sensors while there. I'm out of town on business and won't be back for about a week and a half.
Here's a link for repairs... JagRepair.com - Jaguar Repair Information Resource
Here's a pdf of the engines AJ26/AJ27... http://www.jagrepair.com/images/Trai...ual-9-5-01.pdf
...and here's a pic of the knock sensor locations "KS" (pg 20 of pdf link)...

 

Last edited by Highhorse; 02-01-2018 at 08:55 PM.
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