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Discussion Starter #1
Hi

Hoping everyone is ok

I am new here and please forgive me for my lack of knowledge or being able to explain my problem correctly.

A month ago I started to notice a weird problem, whilst accelerating my jaguar would splutter and lose power for a second then the power would kick back in. Like for a split second it was about to cut out and then drive normally.

To date I have had a new bypass valve fitted, apparently it allows air to both turbos ????? lol I have no idea :rolleyes:
It was changed as the arm had totally snapped off.

maf sensor, fan circuit controller module one. ???

Still, I have this problem, It only happens once from cold and usually happens within 10 minutes of driving then its fine.

No smoke from rear at all, no warning lights on the dash, had it on the computer and there are no codes. ???

The car is very responsive until that happens then its as fast as .... again

I have attached pics of the parts that have been changed.
181741
181742
 

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welcome!

Does it matter how hard you do accelerate to experience this? Have you noticed if this happens at a specific rpm or speed?
 

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Discussion Starter #3
Thank you, Actually a good point, When I am doing 30 mph / 40 mph. A steady speed

When it does happen, it's like its losing power, not getting enough fuel, breathing properly maybe, going to cut out
Not an expert at all!

When it does happen though, I do touch the accelerator a touch more thinking it's going to cut out and the problem does go away. It will drive normally after that.

It was serviced in March 2020.

I did have that restricted performance light on due to the bypass valve failing, but since all works have been done, no codes on computer. No warning lights on dash.

Frustrating lol as I want to sell the vehicle and get a newer model.
 

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Not an expert either but I wonder if it's a throttle body issue (as you mentioned that pushing the accelerator clears it). If you know anyone with an iCarsoft reader, that has a throttle reset function which might be useful. Or tell us where you are and there might be a FM close-by with one.
 

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Discussion Starter #5
I am from Wolverhampton.

Called the local garage that looks after my car and they don't have an iCarsoft reader
 

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I am from Wolverhampton.

Called the local garage that looks after my car and they don't have an iCarsoft reader
I should hope not. It's a tool for us amateurs. They would/should have an all-singing, all-dancing equivalent.
 

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I wonder if this is an accelerator pedal potentiometer issue - cheap and easy enough to try?
 

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Service done in March you said, was it a A or B Service? Fuel filter is changed every 2 years, was that done?
 

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And if it says it was done on the invoice it is still worth checking it WAS actually done. If changed in March it should look pretty new still and may even have the date on it. Some places can 'forget' to change things they think the customer may not see.
 

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Discussion Starter #10
Always a full Service every year, never missed. I was there when the last service was done. He changed the oil, fuel, air and pollen filter.

Car was plugged in last week and not one code showing.

Anyway he's going to take a look at the throttle body when I take it down the weekend. Also plug the computer in and check again.
 

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Thank you, Actually a good point, When I am doing 30 mph / 40 mph. A steady speed

When it does happen, it's like its losing power, not getting enough fuel, breathing properly maybe, going to cut out
Not an expert at all!

When it does happen though, I do touch the accelerator a touch more thinking it's going to cut out and the problem does go away. It will drive normally after that.

It was serviced in March 2020.

I did have that restricted performance light on due to the bypass valve failing, but since all works have been done, no codes on computer. No warning lights on dash.

Frustrating lol as I want to sell the vehicle and get a newer model.
Throttle actuator or pedal was my first thought but you say it happens once from cold.
what if you jump back to car when engine is still warm? If it doesn’t happen, I would say a turbo valve, egr valve or maf sensor (a loose connector?) it also could be fuel rail pressure regulator or fuel flow control valve.

as always I would recommend buying a cable to run SDD because that gives you a chance to read sensors when this happens.
A crack/ loose seal in air intake or vacuum lines that improve by temperature could cause this as well.
 

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Discussion Starter #12
If I drive in the morning, then leave it to stand and drive it later on in the day it will do it again. Once the problem is corrected by pumping the accelerator pedal it will not do it again whilst being driven. Without fault codes showing up on computer its hard to diagnose.
 

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Is it happening at a particular RPM that you've noticed dph?
 

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Is it happening at a particular RPM that you've noticed dph?...
 

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Discussion Starter #16
To be honest I haven't noticed, but when it does do it again I will look to see what's happening on the rpm
 

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The reason for the rpm question is that the second turbo kicks in around 2500 rpm (I’m sure someone will be along soon to give exact figure as I drive a petrol!) so if it is around that point it could indicate an issue.
 
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Did you change both MAF sensors? If not try swapping them around (top to bottom, bottom to top).

ive had a similar issue with my ‘10 3.0d s and the bottom sensor was fouled. I’m waiting for a replacement but I’m the meantime I’ve cleaned it as best I can and swapped it with the top sensor and it’s almost solved the hestitation.

incidentally if you put it into “s”, select 3rd manually and set the cruise to 55mph - how does the car run? does that bring on any of the symptoms?
 

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To be honest I haven't noticed, but when it does do it again I will look to see what's happening on the rpm
I am thinking Of Fuel rail pressure regulator (It’s on left bank) or fuel flow control valve (Center back, a part of HPFP). Specially first one because it’s only mechanical and it happens that valve sticks or spring breaks. Maybe some fuel additives would help clean it.
 

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I've had intermitted issues since i bought mine had bad intake issue, maf and dpf cycle issues, random RP but mainly at top end RP.

Last year I dismantled the intake between the V where the 2 EGR pipes go in and they were completely blocked up like golf balls of soot on each side. If you had issues with air fuel mix this could be helpful.

EGR should be being used at that speed going steady, long shot but its been a year without issue for me now im so happy.

GL

Sent from my Pixel 3 XL using Tapatalk
 
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