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Discussion Starter · #1 ·
Hi all,

Looking for some help/advice/opinions.

To start off, I have a 2000 XJR. Over the last few weeks a very intermittent issue seems to have appeared. Periodically the car seems to have a short surge of acceleration. It only lasts for (at most) a second so really it's just noise as the revs kick-up, very slight increase in speed, then it corrects itself. It only happens under partial throttle. Car is fine when accelerating hard, or when foot is completely off the accelerator (running up to a red light etc).

Before anyone says it, it's not me losing control of my foot!

Throttle body was changed a couple of years ago. Took the liberty of changing the air filter (which was a bit manky).

Any suggestions on a cause?

Cheers all,

Martin
 

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Right, you could try checking the partial load breather attached to left bank and also check for any air leaks in the inlet trunking and the intercooler seals.
You should also check the ign. coils and the state of the spark plugs....when were they last attended to??

Cheers,
Jagman98
 

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Discussion Starter · #4 ·
Spark plugs were replaced 18k ago. I'll second that question on how do you check coil packs?

Wouldn't a leak anywhere on the inlet, breather or intercooler produce a more constant issue? Mines only has the wee "funny turn" every so often.

One thing I thought of was this :-

I've been using the fuel system cleaner BG44K in as high a concentration as can be done. Basically it strips carbon and other crap build-up from the throttle body onwards, cleanes cylinders etc. I just wonder if these wee "moments" are a bit of the crap "going through".

Thoughts?

Thank you for your help so far!
 

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Discussion Starter · #5 ·
Car is going to Jag for an OBD scan, I'll post any codes when I get them. Could someone tell me where the throttle position sensor is, is it part of the throttle body? Can this be cleaned easily enough? Occurred to me that this could be the culprit.
 

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TPS is plugged into the engine loom, it's one of the connections on the t-body, all you can do is clean the connectors, or replace the connectors with the gold pin upgrade from Jaguar - if it is the TPS it'll have logged a P1121 code. Ultimately, if it is, then a refurbed or new t-body is in order.
 

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Discussion Starter · #7 ·
Thanks for this mate. Coming to that conclusion myself. Though, given that this problem only occurs after a good bit of driving I am going to try cleaning the TB, MAF and part load breather. All easy done and could sort it.

If not though, anyone have a place to go for a recon. or new TB (except eBay)?
 

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Discussion Starter · #8 ·
Ok guys, OBD check at Jag... Car is throwing NO codes at all. One thing I have noticed, if I drive a reasonable period of time, stop and engine off (like going into the supermarket) then back out and start again (15 or so mins later), it's seems to crop up. I reckon still seems like sticky throttle body.. Any other suggestions?
 

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Discussion Starter · #10 ·
Yeah I'm going to do that; constant pissing rain in Scotland is holding me back though!

I am having trouble locating TB cleaner in a shop I could walk into and buy. Seems like the only option is online/eBay; anyone know of a shop (halfords or something) that sells decent TB cleaner? If not, is there something I could use as a substitute?
 

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Discussion Starter · #12 ·
I thought so, then I read a TB cleaning guide on the US Jag forum and the guy writing it was very specific about saying it CAN'T be carb. cleaner. I thought maybe one of those Redex type fuel system cleaners on a lint free cloth?
 
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