Jaguar 02 s type R

Sooo had my car decatted today in hopes of solving what i thought was a clogged cat this was Purley to eliminate them from my enquiries as to why my cars is stuttering mid range during acceleration but also my biggest problem at the moment which is the car completely losing power (violently) for a second and then regaining it as if its starved or there is a blockage.

everytime this sudden loss of power happens i check my scanner and the knock sensor has thrown a wobbler, this doesn't bring up the eml but is only there when i scan it so its obviously detecting the knock when the issue occurs.

I've now replaced a bunch of the standard go to parts when experiencing these symptoms and nothing has fixed it so far, i am running out of ideas now and the only thing i have left to check is possible fueling problems or change the MAF out, a lot of people say it will be a vacuum leak but I've changed breather hoses done smoke tests and nothing comes of it, plz help lol

 

Checking the code against AutoData, it says it could be a wiring short to positive, Knock sensor incorrectly tightened, the knock sensor itself or the ECM.

 

Thabks for takong the time to reply, the EML light doesnt iluminate after the problem occurs so im asssuming it isnt a primary issue with the knock sensor fro. What ive experienced the knock sensor is picking up a knock from the engine from whatever is causing this sudden jolt and just tripping the knock sensor to throw this code, im assuming there is a bigger problem that is causing this and not actually the knock sesnor that is at fault

 

Last thing first. Does the knock sensor share common power or a ground with the o2's?

 

If it's going bad but not consistently bad do not expect a code.

You may get a pending code.

Probably worth checking all the issues relating to it as per the workshop manual.

But also check fuel trims - see existing threads - especially at idle.

The electrical diagrams (part of the free download workshop manual) will show what shares what power/ground etc.

 

Why would a.knock sensor cause a mid range spluttering problem?.. it all comes down to fuel imo ie a weak fuel pump, the knock sensor code only comes up as a checked item not as a main eml fault,

 

The car idles.spot on and i have no starting problems either, it is just mid range/WOT that im feeling the problems

 

Just to be positive, the stuttering predates the removal of the cats?

How hard is it to access the knock sensors? My first thought is #1 knock sensor is acting up and being overly sensitive. The computer may be responding normally to what it thinks is a valid input. The perceived knock may not be bad enough to turn on the light right away, but it does store a pending code as it may be more extreme than normal. Call me Mr. Vegas, but I'd be willing to gamble on a new sensor as long as you're not hearing some horrible noise like a bad rod, etc.

If you don't want to spend any money on parts just yet, try swapping the knock sensors and see if the fault follows. If access is difficult, I'd be more inclined to just change it rather than go back in a second time. Maybe swap the known-good #2 sensor into the #1 position, and install the new one in the #2 position just in case the new one is bad from stock. Rare, but it happens.

 

If it is a fuel problem you should see a code. I lost the FP regulator on my 2005 STR and it would drive fine sometimes and then sputter and have no power.

So without a FP code how do know it's a fuel problem?

If you want to eliminate the fuel pressure there is a Schrader fitting on the rear passenger side of the fuel rail. I put my fuel pressure gauge on it and ran the gauge up past the wipers so I could close the hood and drive around while looking at the fuel pressure.

It should move around as your drive as it tries to keep fuel pressure at 45 psi above intake manifold pressure. So under boost you will see a rise in fuel pressure. Mine was spiking all around from 0 psi to over 75 psi! But again if this happening it will throw a code which you don't have.

Your problem sounds electrical and I would just bite the bullet and change 1 or both knock sensors. Consider doing both as they are hard to get to to swap. Remember the system IS telling you it see's something wrong with the knock sensor so stay focused on that for now.
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Any updates? I'd really like to learn about the resolution.

 

Yes please post back if you can.

Remember we are all just guessing and you have the car!
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Hi guys sorry about the delay and i really appreciate the input you are all giving, i basically had the car de-catted as i was looking into if my cats where possibly clogged but the sudden power loss and stuttering still remained so i have ticked the cats off the list as possible problems.

Now i have unearthed another issue which maybe related to my main problem, i am now getting the error code p0171 bank 1 too lean, im being told vacuum leak somewhere which if it is could be the problem thats setting my knock sensor off to pull the timing due to the cylinders misfiring as being too lean.


so now i am on the hunt for this leak and then we shall go from there

 

Can be due to de-catting. Or have you put working cats back on? If you have, might there be ANY (exhaust or not) leak no matter how tiny? Can easily cause that code.

 

The decat pipes are still on but ive noticed theres a slight exhaust seapage where the o2 bung was welded on so im assuming if thats sucking some air in it will be throwing the sensors readings out,
im going to get this sorted and see if it fixes the problem and get back to you, it makes sence as the codes only come up after the decat it never came up before.

If i reset the eml light it drives normal for a bit and then comes up with the lean code and restricted performance again so obviously a sensor is working it out first before tripping the limp mode

 

The sudden power loss and almost immediate come back has all the earmarks of something that would trigger restricted performance and an rpm cut at 3000 rpm's. It's sudden and kicks in at 3000 on the nose.

The codes you're now getting (P0171, etc.) usually will also trigger the check engine light and restricted performance message and would probably also been triggered long before your cats became plugged.

 

The loss pf power or timing pull happens at variable rpm's sometimes as high as 4-5 k so its sensing a fueling or misfire problem somewhere im thinking, and causing the limp mode

 

Forgot to say it and you probably already know this but EVERY time you read codes. Erase them all before unhooking the reader.

We must have repeatable codes for troubleshooting.

Now you have P0171 but do you still have the Knock sensor code?
Have you erased any codes so far or have you been erasing them after each code check?
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